- Report of the Double-Molybdate Phase Cs2Ba(MoO4)2with a Palmierite Structure and Its Thermodynamic Characterization
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The existence of a novel double-molybdate phase with a palmierite-type structure, Cs2Ba(MoO4)2, is revealed in this work, and its structural properties at room temperature have been characterized in detail using X-ray and neutron diffraction measurements. In addition, its thermal stability and thermal expansion are investigated in the temperature range 298-673 K using high-temperature X-ray diffraction, leading to the volumetric thermal expansion coefficient αV ≈ 43.0 × 10-6 K-1. The compound's standard enthalpy of formation at 298.15 K has been obtained using solution calorimetry, which yielded ΔfHm°(Cs2Ba(MoO4)2, cr, 298.15 K) = -3066.6 ± 3.1 kJ· mol-1, and its standard entropy at 298.15 K has been derived from low-temperature (2.1-294.3 K) thermal-relaxation calorimetry as Sm°(Cs2Ba(MoO4)2, cr, 298.15 K) = 381.2 ± 11.8 J K-1 mol-1.
- Colineau, Eric,De Zoete, Nathan,Griveau, Jean-Christophe,Rutten, Maikel,Smith, Anna L.,Van Eijck, Lambert
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- Structural and Thermodynamic Investigation of the Perovskite Ba2NaMoO5.5
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Neutron diffraction, X-ray absorption spectroscopy (XAS), and Raman spectroscopy measurements of the quaternary perovskite phase Ba2NaMoO5.5 have been performed in this work. The cubic crystal structure in space group Fm3ˉ m has been
- Bou?xière, Daniel,Clavier, Nicolas,Epifano, Enrica,Guéneau, Christine,Kauric, Guilhem,Martin, Philippe M.,Smith, Anna L.,Van Eijck, Lambert
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- Synthesis, crystal structure and TEM study of the new hollandite-type Ba～8/7Mo8O16
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Investigation of the Cs-Ba-Mo-O system by fused salt electrolysis at 960°C has led to the new related-hollandite compound Ba～8/7Mo8O16. Single-crystals of Ba～8/7Mo8O16 were examined by electron diffraction and high-resolution electron microscopy. Ba～8/7Mo8O16 was found to present a tetragonal I basic unit-cell (a=10.21 A?, c=2.89 A?) with a one-dimensional modulation of wavevector q close to 4/7 along c* at room temperature. Refinement of the crystal structure was made on X-ray single crystal data in the seven-fold supercell in the three-dimensional space group I4 (a=10.214(2) A?, c=20.255(5) A?, Rw(F2)=0.0844 for all 7767 independent reflections and 149 parameters). In the latter supercell approach, the Mo atoms in the double edge-sharing rutile-type chains form Mo3 triangles and planar rhomboidal Mo4 clusters that coexist in equal proportions. The Mo-Mo distances vary from 2.5341(8) to 2.696(2) A? and from 2.5341(8) to 2.894(4) A? in the Mo3 and Mo4 clusters, respectively. The shortest intercluster distance is 3.047(4) A?. The Mo-O distances range between 1.81(1) to 2.418(8) A? as usually observed in reduced molybdenum oxides. The Ba2+ cations occupy the large square channels in square prismatic environment of oxygen atoms with the distribution sequence ...Ba-□-Ba-Ba-□Ba-□-....
- Barrier,Gougeon,Retoux
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- Structural and electrical properties of double perovskite: (BaSr)FeMoO6
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In this article, the structural, micro-structural, and temperature-frequency dependence of electrical characteristics of double perovskite (BaSr)FeMoO6 have been reported. The compound crystalizes in cubic symmetry with lattice parameter a = 7.9280 (2) ?, and V = 245.95 (?)3. The micro-structural study suggests the uniform distribution of grains on its surface with small voids. The obtained high dielectric constant and low tangent loss value may be applicable for capacitor. In the impedance analysis we observed the behaviour of negative as well as positive temperature co-efficient of resistance. The study of the Nyquist plot suggests the existence of only grain effect. Based on both impedance and modulus spectroscopy, dielectric relaxation process is found to be of a non-Debye type. The frequency dependence of conductivity obeys the Jonscher's Power law which suggests the conduction phenomenon follows the non-overlaping small polaron tunnelling and correlated barrier hopping models. The calculated activation energy in the conduction process may be used in electron hoping. The comparative study of Z?? and M?? with frequency suggests the existence of short range ordering of charge carriers. The leakage current study reveals that the conduction mechanism follows the space charge limited conduction phenomenon.
- Choudhary, R. N. P.,Das, Rutuparna
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- HEATS OF FORMATION OF SOME SODIUM AND BARIUM VANADATES AND MOLYBDATES.
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An isoperibol room-temperature calorimeter has been constructed to measure the spontaneous reactions of BaO and Na//2O with MoO//3 and V//2O//5 after ignition. With this calorimeter, the heats of formation from the component oxides have been determined fo
- Kubaschewski,Hoster,Schlim
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- Photoluminescence properties of BaMoO4 amorphous thin films
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BaMoO4 amorphous and crystalline thin films were prepared from polymeric precursors. The BaMoO4 was deposited onto Si wafers by means of the spinning technique. The structure and optical properties of the resulting films were characterized by FTIR reflectance spectra, X-ray diffraction (XRD), atomic force microscopy (AFM) and optical reflectance. The bond Mo-O present in BaMoO4 was confirmed by FTIR reflectance spectra. XRD characterization showed that thin films heat-treated at 600 and 200 °C presented the scheelite-type crystalline phase and amorphous, respectively. AFM analyses showed a considerable variation in surface morphology by comparing samples heat-treated at 200 and 600 °C. The reflectivity spectra showed two bands, positioned at 3.38 and 4.37 eV that were attributed to the excitonic state of Ba2+ and electronic transitions within MoO2-4, respectively. The optical band gaps of BaMoO4 were 3.38 and 2.19 eV, for crystalline (600 °C/2 h) and amorphous (200 °C/8 h) films, respectively. The room-temperature luminescence spectra revealed an intense single-emission band in the visible region. The PL intensity of these materials was increased upon heat-treatment. The excellent optical properties observed for BaMoO4 amorphous thin films suggested that this material is a highly promising candidate for photoluminescent applications.
- Marques, Ana Paula Azevedo,De Melo, Dulce M.A.,Longo, Elson,Paskocimas, Carlos A.,Pizani, Paulo S.,Leite, Edson R.
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- Formation of periodic precipitation patterns: A moving boundary problem
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A new scenario for the formation of Liesegang patterns is proposed. The periodic precipitation pattern formation in a gel column is interpreted as a moving boundary problem. The existing time law, space law, and width law are revisited and reformulated on the basis of a moving boundary assumption and more meaningful explanations are given. All the new equations suggested were found to be in good agreement with experimental observations.
- George, Jacob,Varghese, George
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- Thermal stability of alkali and alkaline-earth substituted LAMOX oxide-ion conductors
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The high temperature demixing/recombination phenomenon previously observed in Ca-substituted La2Mo2O9 oxide ion conductors [A. Selmi et al., Solid State Ionics, 2006, 177, 3051; Eur. J. Inorg. Chem., 2008, 1813] has been visualised using scanning electron microscopy and EDX analysis. The demixed state appears as CaMoO4 straight solid streams erupted from pores within LAMOX grains. The thermal stability study is extended to other alkali and alkaline-earth substituted LAMOX compounds, all of which are shown, in temperature-controlled X-ray diffractograms, to present similar demixing/recombination processes. The most spectacular effect is observed in La1.88K0.12Mo0.6W1.4O 8.88 where demixing takes the form of a total decomposition, before full recombination at a higher temperature. Such a phenomenon is interpreted as originating from temperature-dependent solid solution limits with higher substitutional ranges at higher temperatures. It results in the metastabilisation of pure phases by quenching (or rapid cooling), whereas the stable state is demixed, as shown on slowly cooled samples. The Royal Society of Chemistry 2010.
- Selmi,Galven,Corbel,Lacorre
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- Novel carbon and sulfur-tolerant anode material FeNi3?PrBa(Fe,Ni)1.9Mo0.1O5+:δ for intermediate temperature solid oxide fuel cells
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Suppression of carbon deposition and sulfur poisoning without sacrificing electrochemical performance is crucial for operating solid oxide fuel cells (SOFCs), especially at intermediate temperatures (IT). In this work, nickel-doped A-site deficient perovskite oxides (PrBa)0.95Fe1.9-xNixMo0.1O6-δ (PBFMNix, x = 0, 0.1, 0.2, 0.3, 0.4) were synthesized and investigated as potential anodes for IT-SOFCs. With increased amounts of Ni2+, the ratios of Fe2+/Fe3+ and Mo5+/Mo6+ in as-prepared PBFMNix continuously decreased under a charge-compensating mechanism, which simultaneously depressed the formation of the impurity phase (BaMoO4). Interestingly, the substitution of Ni2+ benefits the reduction of Fe3+ to Fe2+ and Mo6+ to Mo5+, and small portions of Fe and Ni elements are exsolved from the parent oxides, forming FeNi3 alloy nano-particles that greatly accelerate the chemical adsorption and surface reaction kinetics of H2, and thus improve the electrochemical performances of oxide-based anodes. Transformation of the electrical conduction from p-type to n-type after reduction was also observed. A very small polarization resistance of 0.028 Ω cm2 at 750 °C was achieved for the cell with the PBFMNi0.3 anode. Importantly, fueled with syngas with 50 ppm H2S, the maximum power density of a button cell based on the PBFMNi0.3 anode and an Sm0.2Ce0.8O1.9 (SDC) electrolyte-supporting configuration can reach 498 mW cm-2 at 750 °C, and long-term stability over 100 hours can be demonstrated with negligible performance decay. All these results indicate that PBFMNi0.3 is a promising high-performance anode material with good coking resistance and sulfur tolerance in intermediate temperatures.
- Xue, Shuangshuang,Shi, Nai,Wan, Yanhong,Xu, Zheqiang,Huan, Daoming,Zhang, Shaowei,Xia, Changrong,Peng, Ranran,Lu, Yalin
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- New microwave dielectric ceramics BaLn2(MoO4) 4 (Ln = Nd and Sm) with low loss
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In the present work, a pure monoclinic phase of BaNd2(MoO 4)4 and BaSm2(MoO4)4 was formed at 850°C and 600°C, respectively, via a solid-state reaction method. The ceramic samples were found
- Zhou, Di,Pang, Li-Xia,Guo, Jing,Wu, Ying,Zhang, Gao-Qun,Dai, Wei,Wang, Hong,Yao, Xi
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- Order and Disorder: Toward the Thermodynamically Stable α-BaMoO2F4from the Metastable Polymorph
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A fully ordered noncentrosymmetric barium molybdenum oxyfluoride, α-BaMoO2F4, has been synthesized by a hydrothermal reaction at 200 °C in a concentrated hydrofluoric acid solution. A centrosymmetric polymorph with O/F disorder, β-BaMoO2F4, has been obtained in several minutes when the reaction mixture was stirred at room temperature in the same medium. Interestingly, we found that the metastable β-BaMoO2F4 transforms into the thermodynamically stable α-BaMoO2F4 in an ambient condition. More detailed kinetic studies using powder X-ray diffraction indicate that the MoO2F4 octahedra in the kinetic phase, β-BaMoO2F4, rearrange through the constant dissolution/precipitation process to find a more stable orientation and form the fully ordered α-BaMoO2F4. Density functional theory (DFT) calculations suggest that the formation of the thermodynamically stable α-BaMoO2F4 is driven by the strong Mo-O π-interactions induced by Ba2+ cations. The new finding on the understanding of the kinetics of solid-state reactions suggests a novel way toward an effective discovery of functional materials with asymmetric structures.
- Jo, Hongil,Lee, Min Hyung,Ok, Kang Min
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- Synthesis and structural characterization of Ba(Ln 2/3 IIIB1/3VI)O3 (LnIII=Dy, Gd and Sm; BVI=Mo or W) complex perovskites
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We describe in this work the synthesis and crystal structure of five rare earth and Mo(VI) or W(VI) containing complex perovskites. The compounds studied are Ba(Dy2/3Mo1/3)O3, Ba(Dy2/3W 1/3)O3, Ba(Gd2/3Mo1/3)O 3, Ba(Gd2/3W1/3)O3 and Ba(Sm 2/3W1/3)O3 and were prepared starting from solutions, by the polymeric precursors method. Structural characterization by HREM, SAED and powder XRD revealed the five compounds to be ordered cubic perovskites, SG Fm-3m (225), with a cell parameter double of that of a simple perovskite cell and increasing as the size of the trivalent lanthanide ion increases (DyGdSm).
- Fuentes, Antonio F.,Garza-Garcia,Escalante-Garcia,Mendoza-Suarez,Boulahya, Khalid,Amador
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- Erbium-Doped Upconversion Phosphor in the Li2MoO4–BaMoO4–Y2(MoO4)3 System
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Abstract—: We have investigated subsolidus phase equilibria in the Li2MoO4–BaMoO4–Y2(MoO4)3 system and constructed its phase compatibility diagram. A ternary molybdate with the composition Li3Ba2Y3(MoO4)8 and a monoclinic scheelite-like structure (sp. gr. C2/c) has been identified on the BaMoO4–LiY(MoO4)3 join. Doping Li3Ba2Y3(MoO4)8 with Er3+ ions, we obtained a Li3Ba2Y2.85Er0.15(MoO4)8 upconversion phosphor possessing efficient anti-Stokes luminescence in the range 530–850 nm under IR excitation (λex = 977 nm). The synthesized phosphor has been characterized by X-ray diffraction, differential thermal analysis, and IR spectroscopy.
- Batueva, S. Yu.,Kozhevnikova, N. M.
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- Neutron diffraction study of the crystal structure of BaMoO4: A suitable precursor for metallic BaMoO3 perovskite
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BaMoO3, metallic and Pauli paramagnetic, has been prepared by controlled reduction of BaMoO4. This precursor, containing Mo(VI), is unusually stable against reduction, due to structural factors. The crystal structure of BaMoO4 has been refined from neutron powder diffraction data: space group I41/a (no. 88), Z=4, a=5.5479(9), and c=12.743(2) A. A bond-valence study allowed us to detect the presence of slight tensile and compressive stresses in the crystal structure of BaMoO4, in which Ba is overbonded and Mo is underbonded. However, this effect is less pronounced than in other AMO4 oxides with a scheelite structure (A=Ca, Sr, Ba; M=Mo, W): BaMoO4 contains the M cation exhibiting the closest valence to the nominal value of 6+, suggesting a large covalent contribution to the Mo-O bonds. This observation is coherent with the large thermal stability of this compound against reduction, taking place at temperatures above 920°C in H2 flow.
- Nassif, Vivian,Carbonio, Raul E.,Alonso, Jose A.
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- Magnetic and structural studies of the double perovskites Ba 2REMoO6
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A magnetic, electronic and structural study of the double perovskites Ba2REMoO6 (RE=Sm, Eu, Gd, Dy) has been performed. All materials crystallise in the cubic Fm3?m symmetry space group and the cell volume decreases as RE varies from Sm to Dy in accordance with Vegard's law. An antiferromagnetic transition is observed below TN=130 and 112 K for RE=Sm and Eu, respectively. The Néel temperatures of these ordered rare earth molybdenum double perovskites are much higher than previously observed in double perovskites containing Eu or Sm and a 4d or 5d transition metal arranged in an ordered rock salt configuration. The high Néel temperatures arise due to a strong superexchange magnetic interaction via the Mo-O-RE-O-Mo pathway. All of the phases are electronically insulating and there is no evidence of magnetoresistance at any temperature.
- McLaughlin
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- Aqueous mineralization process to synthesize uniform shuttle-like BaMoO4 microcrystals at room temperature
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Single-crystalline BaMoO4 microcrystals with uniform shuttle-like morphology have been successfully prepared via a facile aqueous solution mineralization process at room temperature. It was found that the pH value and the reaction temperature had important influences on the formation of the BaMoO4 microcrystals. The shuttle-like microcrystals can be obtained in alkaline aqueous solution (pH=9-14), and when the pH value was adjusted to 6-7, cocoon-like microcrystals appeared. A possible two-stage growth process has been proposed, and the Ostwald ripening was responsible for the formation of the shuttle-like BaMoO4 microcrystals. The products were characterized by XRD, XPS, FESEM, HRTEM and Raman spectroscopy. Room-temperature photoluminescence indicated that the as-prepared BaMoO4 microcrystals had a strong blue emission peak centered at 438 nm.
- Wu, Xueying,Du, Jin,Li, Haibo,Zhang, Maofeng,Xi, Baojuan,Fan, Hai,Zhu, Yongchun,Qian, Yitai
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- Solvothermal morphology studies: Alkali and alkaline earth molybdates
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A convenient and systematic solvothermal pathway towards alkali and alkaline-earth molybdates has been established. The solvothermal treatment of a molybdenum-based precursor material (yellow molybdic acid, MoO 3·2H2O) with ionic additives (alkali or alkaline-earth halides) provides access to a spectrum of molybdates. Their particle morphology can further be addressed by optimizing the reaction conditions. The resulting products cover a wide scope of sizes and morphologies, ranging from molybdenum oxide fibres with high aspect ratios and nanoscale diameters to millimeter-sized crystals of novel alkali molybdates. Both anionic and cationic additives exhibit certain synthetic profiles that offer the perspective of turning this approach into a 'toolbox' for the tailoring of molybdate-based materials.
- Michailovski, Alexej,Krumeich, Frank,Patzke, Greta R.
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- Phase formation, structural and microstructural characterization of novel oxynitride-perovskites synthesized by thermal ammonolysis of (Ca,Ba)MoO4 and (Ca,Ba)MoO3
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Reactions of AMoO4 and AMoO3 (A=Ca2+, Ba2+) with ammonia were investigated at 873 K3 and to study their crystal structure. CaMo(O,N)3 and BaMo(O,N)3 were prepared by thermal ammonolysis of the corresponding CaMoO3 and BaMoO3 precursors at T=898 and 998 K, respectively. The structural parameters of the oxynitrides were obtained from Rietveld refinements of X-ray and neutron powder diffraction data. CaMo(O,N)3 crystallizes in the GdFeO3 distorted perovskite structure with orthorhombic space group Pbnm and a=5.5029(1) A, b=5.5546(1) A, c=7.8248(1) A as determined by X-ray powder diffraction. Its O/N content refined from the neutron diffraction data corresponds to the composition CaMoO1.7(1)N1.3(1). BaMo(O,N)3 crystallizes in the cubic perovskite structure with space group Pm3m and a=4.0657(1) A as determined by X-ray powder diffraction. Transmission electron microscopy reveals a complex microstructure for both CaMoO3 and CaMoO1.7(1)N1.3(1) represented by twin domains of different orientation.
- Logvinovich,Aguirre,Hejtmanek,Aguiar,Ebbinghaus,Reller,Weidenkaff
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- Microwave-assisted synthesis of barium molybdate by a citrate complex method and oriented aggregation
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BaMoO4 powders, which have scheelite type structure, were successfully synthesized at low temperatures by a modified citrate complex method assisted by microwave irradiation. The citrate complex precursors were heat-treated at temperatures from 300 to 500 °C for 3 h. Crystallization of the BaMoO4 powders were detected at 350 °C, and completed at a temperature of 400 °C. TEM image of the BaMoO4 product obtained above 400 °C revealed spindle-rods-like or flake-like morphology. The anisotropic growth habit of BaMoO4 leads to the oriented aggregation, which is attributed to the high chemical potentials of the intrinsic structure of BaMoO4. The BaMoO4 powder prepared at 500 °C showed the strongest photoluminescent intensity.
- Ryu, Jeong Ho,Yoon, Jong-Won,Lim, Chang Sung,Shim, Kwang Bo
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- Synthesis, Characterization and Optical Properties of BaMoO4 Synthesized by Microwave Induced Plasma Method
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BaMoO4 crystals were synthesized by a 900 W microwave induced plasma process (MIP) for 40, 60, 120 and 140 min. Phase, morphology, vibrational mode and energy gap were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and UV-visible spectroscopy. In this research, the phase and morphology of product were influenced by microwave heating time. The sample processed for 140 min shows spherical particles tetragonal BaMoO4 phase with size of 200–700 nm in diameter. BaMoO4 with band gap of 3.35 eV shows a blue emission wavelength at 440 nm.
- Klinbumrung, Arrak,Phuruangrat, Anukorn,Thongtem, Titipun,Thongtem, Somchai
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- BaMoO4 powders processed in domestic microwave-hydrothermal: Synthesis, characterization and photoluminescence at room temperature
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In this paper, BaMoO4 powders were prepared by the coprecipitation method and processed in a domestic microwave-hydrothermal. The obtained powders were characterized by X-ray diffraction (XRD), Fourier transform Raman (FT-Raman) spectroscopy, ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurements. The morphology of these powders were investigated by scanning electron microscopy (SEM). SEM micrographs showed that the BaMoO4 powders present a polydisperse particle size distribution. XRD and FT-Raman analyses revealed that the BaMoO4 powders are free of secondary phases and crystallize in a tetragonal structure. UV-vis was employed to determine the optical band gap of this material. PL measurements at room temperature exhibited a maximum emission around 542 nm (green emission) when excited with 488 nm wavelength. This PL behavior was attributed to the existence of intrinsic distortions into the [MoO4] tetrahedron groups in the lattice.
- Cavalcante,Sczancoski,Tranquilin,Joya,Pizani,Varela,Longo
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- Catalytic behavior of AMoOx (A = Ba, Sr) in oxidation of 2-propanol
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Perovskite-type oxides, BaMoO3 and SrMoO3, were prepared by reduction of scheelite-type oxides, BaMoO4 and SrMoO4, in H2 flow at 873 K and characterized by XRD, TG, SEM, TPR, NH3-TPD, UV-vi
- Kubo, Jun,Ueda, Wataru
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- Microwave and infrared dielectric response of temperature stable (1-x) BaMoO 4-x TiO 2 composite ceramics
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The (1-x)BaMoO4-xTiO2 (x = 0.0, 0.2, 0.3, 0.338, 0.4, 0.5, 0.66) ceramics were synthesized by the conventional mixed-oxide process. The sintering behaviors, phase composition, chemical compatibility with silver, and microwave dielectric properties of pure (1-x)BaMoO4-xTiO 2 ceramics and 0.662BaMoO4-0.338TiO2 ceramic with H3BO3-CuO addition were studied. Infrared reflectivity spectra of (1-x)BaMoO4-xTiO2 (0.2 ≤ x a;circ 0.4) composites were measured in the range of 50-4500 cm-1 at room temperature. X-ray diffraction analysis reveals that scheelite BaMoO 4 and rutile TiO2 phase coexist with each other at 1275°C and both of them do not react with silver (Ag) at 850°C. When the mole fraction of TiO2 (x value) is 0.4, a temperature stable microwave dielectric material is obtained, with εr = 13.8, Q × f = 40 500 GHz (f = 8.02 G), and τf = -6.13 ppm/°C. Complex dielectric spectra gained from the infrared spectra were extrapolated down to microwave range, and they were in good agreement with the measured microwave permittivity and dielectric losses. With 5 wt% H3BO 3 and 1 wt% CuO addition, the 0.662BaMoO4-0.338TiO 2 ceramics can be sintered well below 900°C, and possess good microwave dielectric properties with εr = 14, Q × f = 48 360 GHz, and τf = +13.9 ppm/°C.
- Guo, Jing,Zhou, Di,Wang, Hong,Chen, Yuehua,Zeng, Yi,Xiang, Feng,Wu, Ying,Yao, Xi
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- Controllable route to barium molybdate crystal and their photoluminescence
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A simple precipitation route has been developed to synthesize BaMoO4 with different morphologies, such as flower-like spheres, spindle-like and octahedron crystals, by using a novel organic compounds poly-(styrene-alt-maleic acid) (PSMA) as crystal growth modifier. The concentrations of PSMA and reactants have significant influences on the morphology control of BaMoO4. PSMA efficiently controls the morphology by inhibiting the oriented growth direction. The photoluminescence spectra show broad green emission at 530 nm, which is attributed to the 1T2 → 1A1 transition in the intrinsic MoO42- group.
- Lei,Ye,Ding,Bi,Xiao,Sun,Fan,Yang,Wang
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- Simultaneous presence of (Si3O10)8- and (Si2O7)6- groups in new synthetic mixed sorosilicates: BaY4(Si2O7)(Si3O 10) and isotypic compounds, studied by single-crystal X-ray diffraction, Raman spectroscopy and DFT calculations
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Three new, isotypic silicate compounds, BaY4(Si 2O7)(Si3O10), SrYb 4(Si2O7)(Si3O10) and SrSc4(Si2O7)(Si3O10), were synthesized using high-temperature flux growth techniques, and their crystal structures were solved from single-crystal X-ray intensity data: monoclinic, P21/m, with a=5.532(1)/5.469(1)/5.278(1), b=19.734(4)/19.447(4)/19.221(4), c=6.868(1)/6.785(1)/6.562(1) A, β=106.53(3)/106.20(3)/106.50(3), V=718.8(2)/693.0(2)/638.3(2) A3, R(F)=0.0225/0.0204/0.0270, respectively. The topology of the novel structure type contains isolated horseshoe-shaped Si3O 10 groups (Si-Si-Si=93.15-95.98), Si2O7 groups (Si-Obridge-Si=180, symmetry-restricted) and edge-sharing M(1)O 6 and M(2)O6 octahedra. Single-crystal Raman spectra of the title compounds were measured and compared with Raman spectroscopic data of chemically and topologically related disilicates and trisilicates, including BaY2(Si3O10) and SrY2(Si 3O10). The band assignments are supported by additional theoretical calculation of Raman vibrations by DFT methods.
- Wierzbicka-Wieczorek, Maria,Toebbens, Daniel M.,Kolitsch, Uwe,Tillmanns, Ekkehart
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- Microwave-assisted synthesis of BaMoO4 nanocrystallites by a citrate complex method and their anisotropic aggregation
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BaMoO4 powders, which have scheelite-type structure, were successfully synthesized at low temperatures by a modified citrate complex method assisted by microwave irradiation. The citrate complex precursors were heat-treated at temperatures from 300 to 500 °C for 3 h. Crystallization of the BaMoO4 powders were detected at 350 °C and completed at a temperature of 400 °C. TEM image of the BaMoO4 product heat-treated at 400 °C revealed spindle-rods-like and flake-like morphology at 500 °C. The anisotropic aggregation habit of BaMoO4 lead to two-dimensionally aggregated powder morphology, which was attributed to the high chemical potentials of the intrinsic structure of BaMoO4.
- Ryu, Jeong Ho,Yoon, Jong-Won,Shim, Kwang Bo
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- Magnetic and magneto-transport properties of (Ba0.8 Sr0.2)2 - x Ndx FeMoO6
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The variation in structural, magnetic and magneto-transport properties of the double perovskite system (Ba0.8Sr0.2)2-xNdxFeMoO6?{0.03+ doping (electron doping) has been
- Pandey, Vibhav,Verma, Vivek,Aloysius,Bhalla,Kotnala
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- Novel electrochemical technique: Grain control in preparation of polycrystalline BaMoO4 film
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BaMoO4 films have been prepared by a novel electrochemical technique without impressed current on molybdenum substrates at room temperature in barium hydroxide aqueous solution. In order to form desired surface morphology and grain size, the BaMoO4 crystal grains have been controlled effectively by adjusting ion-concentration and adding adequate surfactant. The as-prepared BaMoO4 films have been characterized by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). SEM and XRD results indicate that the morphology, grain size, phase and crystallinity were significantly developed.
- Cui, Chunhua,Bi, Jian,Wu, Chunyan,Zhang, Shu,Gao, Daojiang
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- An investigation of the optical properties and water splitting potential of the coloured metallic perovskites Sr1?xBaxMoO3
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The solid solution Sr1?xBaxMoO3 (x=0.00, 0.025, 0.050, 0.075, 0.100 and 1.00) has been synthesised. Rietveld refinement of X-ray diffraction data shows that all materials crystallise with cubic (Pm-3m) symmetry and that a miscibility gap exists from x=0.1–1.0. The optical properties of the metallic perovskites Sr1?xBaxMoO3 have been investigated by a combination of UV–vis spectroscopy and density functional theory (DFT). Upon increasing x from 0 to 1 in Sr1?xBaxMoO3 there is a reduction in the measured band gap from 2.20?eV to 2.07?eV. The measured band gap is attributed to the electronic transition from the Mo 4d t2g band to the eg band. The potential of SrMoO3 and BaMoO3 as water-splitting photocatalysts was explored but there was no evidence of hydrogen or oxygen evolution, even with the presence of a Pt co-catalyst.
- Hopper,Le,Cheng,Weller,Marschall,Bloh,Macphee,Folli,Mclaughlin
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- Barium molybdate and barium tungstate nanocrystals synthesized by a cyclic microwave irradiation
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BaMoO4 and BaWO4 nanocrystals were synthesized from Ba(NO3)2 and Na2MeO4 (Me=Mo and W) solutions using 50% of 600 W microwave irradiation for 20 min. The products were characterized using X
- Phuruangrat, Anukorn,Thongtem, Titipun,Thongtem, Somchai
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- Room-temperature preparation of BaMoO4 nano-oetahedra by mieroemulsion method
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Uniform barium molybdate nano-octahedra with a mean edge length of 50 nm have been prepared in Triton X-100 water-in-oil (w/o) microemulsions at room temperature. BaMoO4 nano-octahedra present tetragonal single crystals. The size of these nano-
- Mi, Yan,Huang, Zaiyin,Zhou, Zeguang,Hu, Feilong,Meng, Qiufeng
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- Combining second-order Jahn-Teller distorted cations to create highly efficient SHG materials: Synthesis, characterization, and NLO properties of BaTeM2O9 (M = Mo6+ or W6+)
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Two new oxides, BaTeMo2O9 and BaTeW2O9, have been synthesized, by standard solid-state techniques, that have strong SHG intensities of 600 × SiO2, on the order of LiNbO3. Both materials contain cations susceptible to second-order Jahn-Teller (SOJT) distortions, resulting in asymmetric coordination environments. The SOJT distortion polarizes the M6+-O and Te4+-O bonds. Equally importantly, these polarizations constructively add, resulting in the large SHG responses. Powder SHG measurements on BaTeM2O9 (M = Mo6+ or W6+) indicated that both materials are phase-matchable and have a (deff)exp of 28 and 22 pm/V, respectively. Using bond hyperpolarizability values (β's) of 130 × 10-40 and 305 × 10-40 m4/V for Te4+-O and Mo6+-O respectively, we calculate a deffcalc of 20pm/V for BaTeMo2O9. In addition, through the powder SHG measurements, we are able to give a more reasonable value for β(W6+-O), 230 × 10-40 m4/V. This value is consistent with the smaller polarizability and magnitude of the intra-octahedral distortion of W6+ compared with Mo6+. Copyright
- Ra, Hyun-Seup,Ok, Kang Min,Halasyamani, P. Shiv
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- Electrical conductivity and thermal expansion behavior of MMoO4 (M = Ca, Sr and Ba)
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Abstract Alkaline earth (Ca, Sr, Ba) molybdates were synthesized by solid state reaction route. The compounds were characterized by powder-XRD, TG-DTA techniques. The electrical conductivities of these compounds were measured by AC-impedance technique at
- Maji, Binoy Kumar,Jena, Hrudananda,Asuvathraman,Kutty, K.V. Govindan
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- Single phase melt processed powellite (Ba,Ca)MoO4 for the immobilization of Mo-rich nuclear waste
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Crystalline and glass composite materials are currently being investigated for the immobilization of combined High Level Waste (HLW) streams resulting from potential commercial fuel reprocessing scenarios. Several of these potential waste streams contain elevated levels of transition metal elements such as molybdenum (Mo). Molybdenum has limited solubility in typical silicate glasses used for nuclear waste immobilization. Under certain chemical and controlled cooling conditions, a powellite (Ba,Ca)MoO4 crystalline structure can be formed by reaction with alkaline earth elements. In this study, single phase BaMoO4 and CaMoO4 were formed from carbonate and oxide precursors demonstrating the viability of Mo incorporation into glass, crystalline or glass composite materials by a melt and crystallization process. X-ray diffraction, photoluminescence, and Raman spectroscopy indicated a long range ordered crystalline structure. In situ electron irradiation studies indicated that both CaMoO4 and BaMoO4 powellite phases exhibit radiation stability up to 1000 years at anticipated doses with a crystalline to amorphous transition observed after 1 × 1013 Gy. Aqueous durability determined from product consistency tests (PCT) showed low normalized release rates for Ba, Ca, and Mo (2).
- Brinkman, Kyle,Fox, Kevin,Marra, James,Reppert, Jason,Crum, Jarrod,Tang, Ming
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- Influence of the cation size on the framework structures and space group centricities in AMo2O5(SeO3)2 (A = Sr, Pb, and Ba)
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Two new quaternary mixed-metal selenites, SrMo2O 5(SeO3)2 and PbMo2O 5(SeO3)2, have been synthesized as crystals and pure polycrystalline phases by standard solid-state reactions using SrMoO 4, PbO, MoO3, and SeO2 as reagents. The crystal structures of the reported materials have been determined by single-crystal X-ray diffraction. SrMo2O5(SeO3)2 and PbMo2O5(SeO3)2 are isostructural and crystallized in the triclinic centrosymmetric space group P1 (No. 2). The reported materials exhibit chain structures consisting of MoO6 octahedra and asymmetric SeO3 polyhedra. Complete characterizations including IR spectroscopy and thermal analyses for the compounds are also presented, as are dipole moment calculations. In addition, the powder second-harmonic-generating (SHG) properties of noncentrosymmetric polar BaMo2O5(SeO3)2 have been measured using 1064 nm radiation. Through powder SHG measurement, we are able to determine that BaMo2O5(SeO3)2 has a SHG efficiency of approximately 80 times that of α-SiO2. Additional SHG measurements reveal that the material is phase-matchable (type 1). A detailed cation size effect on the symmetry and framework structure is discussed.
- Oh, Seung-Jin,Lee, Dong Woo,Ok, Kang Min
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- Metal-Doping of La5.4MoO11.1 Proton Conductors: Impact on the Structure and Electrical Properties
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La5.4MoO11.1 proton conductors with different metal doping (Ca2+, Sr2+, Ba2+, Ti4+, Zr4+, and Nb5+) have been prepared and structurally and electrically characterized.
- López-Vergara, Adrián,Porras-Vázquez, José M.,V?llestad, Einar,Canales-Vazquez, Jesús,Losilla, Enrique R.,Marrero-López, David
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- Fabrication of AMoO4 (A = Ba, Sr) film on Mo substrate by solution reaction assisted ball-rotation
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Alkaline earth molybdates, such as BaMoO4 and SrMoO4, films have been successfully fabricated on a Mo metal substrate in AOH (A = Ba, Sr) solutions by a ball-rotation-assisted solution reaction, at room temperature. The dissolution of Mo was mainly controlled by the concentration of the H2O2 oxidizing agent and ball-rotation to form MoO42- in the solution. AMoO4 was deposited on the substrate by the reaction between MoO42- and A2+ ions without any high energy or high-temperature treatment. Also, the mass transport of alkaline earth ions onto the solid/solution interface was improved as a result of the vigorous solution agitation by the ball-rotation. Therefore, the rate of deposition of the AMoO4 films was accelerated by the ball-rotation. A decrease in the grain size of the film was observed with an excessive ball-rotation.
- Rangappa, Dinesh,Fujiwara, Takeshi,Watanabe, Tomoaki,Yoshimura, Masahiro
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- Novel shape evolution of BaMoO4 microcrystals
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Dendritic BaMoO4 microcrystals with lengths of about 5-15 μm were synthesized simply under ambient conditions by a microemulsion-mediated method within an ultrashort time. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and field-emission scanning electron microscopy (FESEM), which showed that the products were in pure tetragonal BaMoO4 structure and that an individual dendrite had a long central stem with four array shrunken branches. Detailed studies revealed that the formation of these 3-D structures was strongly dependent on the composition of the microemulsion. At prolonged aging time, the dendrites evolved into rods and further into particles, driven by the lattice distortion energy required to evolve the crystal from a metastable to a stable state. This novel crystal shape evolution provides insight into crystallization behavior given that the growth history and shape evolution process have traditionally been poorly understood.
- Gong, Qiang,Qian, Xuefeng,Cao, Hongliang,Du, Weimin,Ma, Xiaodong,Mo, Maosong
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- Synthesis, characterization and luminescent properties of green phosphor BaMoO4:Tb3+
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The green phosphor BaMoO4:Tb3+ was prepared by sol-gel method. The effects of doping concentration and sintering temperature on the crystal structure and luminescent properties were investigated by X-ray powder diffraction, scanning
- Zhang, Jianfu,Zhu, Lili,Xie, Jianping,Chen, Yuanpeng,Wang, Zhenling
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- Well-defined barium molybdate hierarchical architectures with different morphologies: Controllable synthesis, formation process, and luminescence properties
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Uniform and well-dispersed barium molybdate (BaMoO4) hierarchical microspheres and microflowers have been successfully synthesized via a hydrothermal route by using sodium dodecyl benzenesulfonate (SDBS) as surfactant. The reaction conditions, including SDBS additive, pH value of the initial solution, as well as reaction temperature, have great effect on the size and morphology of the BaMoO4 products. The possible formation process of the BaMoO4 microspheres has been investigated by time-dependent experiments. The as-synthesized BaMoO4:Ln3+ (Ln = Eu, Tb, Dy, and Sm) phosphors show intense characteristic red, green, green-yellow, and orange-red emissions under ultraviolet light excitation, which might find potential applications in the fields of light emitting phosphors, advanced flat panel displays, and light-emitting diodes (LEDs).
- Zhang, Cuimiao,Zhang, Lei,Song, Changying,Jia, Guang,Huo, Shuying,Shen, Shigang
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- Preparation, characterization and electrical conductivity studies of nanocrystalline la doped BaMoO4
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Different compositions of scheelite type nanocrystalline La doped BaMoO4 [Ba1-xLaxMoO4+x/2, where x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5] samples were prepared by acrylamide assisted sol-gel combustion process. Dried gels prepared at 60 °C were heated at different temperatures and characterized using TG/DTA, XRD, FTIR and SEM-EDX techniques. From XRD patterns, crystalline phases for La doped BaMoO4 samples were confirmed and their average crystallite sizes were calculated using Scherrer's formula and it was found to be less than 80 nm. Structure and thermal behavior of scheelite type nanocrystalline La doped BaMoO4 samples were identified respectively using FTIR and TG/DTA measurements. Microstructure and existence of O, La, Ba and Mo elements in the La doped BaMoO4 samples were obtained from SEM-EDX and HRTEMtechniques. The 'd' spacing values were obtained for different (h k l) planes and were well matched with the standard BaMoO4. (h k l) values for different directions of planes were assigned for the observed HRTEM images and were matched with standard BaMoO4. Grain and grain boundary conductivities were evaluated by analyzing the impedance data, using the Winfit software, measured at different temperatures.
- Nallamuthu,Prakash,Satyanarayana,Venkateswarlu
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- Structural disorder in AMoO4 (A = Ca, Sr, Ba) scheelite nanocrystals
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The crystal structure of sub-15 nm AMoO4 (A = Ca, Sr, Ba) scheelite nanocrystals has been investigated using a dual-space approach that combines Rietveld and pair distribution function (PDF) analysis of synchrotron X-ray diffraction data. Rietveld analysis yields an average crystal structure in which the Mo-O bond distance exhibits an anomalously large contraction (2.8%) upon chemical substitution of Ba2+ for Ca2+. Such a dependence on chemical composition contradicts the well-known rigid character of MoVI-O bonds and the resulting rigidity of MoO4 tetrahedra in scheelites. Unlike Rietveld, PDF analysis yields a local crystal structure in which the Mo-O bond distance shows a negligible contraction (0.4%) upon going from Ba2+ to Ca2+ and, therefore, appears independent of the chemical composition. Analysis of the anisotropic displacement parameters of the oxygen atom reveals that the disagreement between the average and local structural models arises from the presence of static orientational disorder of the MoO4 tetrahedra. Rietveld analysis averages the random rotations of the MoO4 tetrahedra across the scheelite lattice yielding an apparent Mo-O bond distance that is shorter than the true bond distance. In contrast, PDF analysis demonstrates that the structural integrity of the MoO4 tetrahedra remains unchanged upon chemical substitution of the alkaline-earth cation, and that their orientational disorder is accommodated through geometric distortions of the AO8 dodecahedra.
- Rabuffetti, Federico A.,Culver, Sean P.,Suescun, Leopoldo,Brutchey, Richard L.
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- Photoluminescent BaMoO4 nanopowders prepared by complex polymerization method (CPM)
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The BaMoO4 nanopowders were prepared by the Complex Polymerization Method (CPM). The structure properties of the BaMoO4 powders were characterized by FTIR transmittance spectra, X-ray diffraction (XRD), Raman spectra, photoluminescence spectra (PL) and high-resolution scanning electron microscopy (HR-SEM). The XRD, FTIR and Raman data showed that BaMoO4 at 300 °C was disordered. At 400 °C and higher temperature, BaMoO4 crystalline scheelite-type phases could be identified, without the presence of additional phases, according to the XRD, FTIR and Raman data. The calculated average crystallite sizes, calculated by XRD, around 40 nm, showed the tendency to increase with the temperature. The crystallite sizes, obtained by HR-SEM, were around of 40-50 nm. The sample that presented the highest intensity of the red emission band was the one heat treated at 400 °C for 2 h, and the sample that displayed the highest intensity of the green emission band was the one heat treated at 700 °C for 2 h. The CPM was shown to be a low cost route for the production of BaMoO 4 nanopowders, with the advantages of lower temperature, smaller time and reduced cost. The optical properties observed for BaMoO4 nanopowders suggested that this material is a highly promising candidate for photoluminescent applications.
- De Azevedo Marques, Ana Paula,De Melo, Dulce M.A.,Paskocimas, Carlos A.,Pizani, Paulo S.,Joya, Miryam R.,Leite, Edson R.,Longo, Elson
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- Tm3+ doped barium molybdate: A potential long-lasting blue phosphor
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Molybdates have applications in various fields such as phosphors, optical fibers, scintillators, magnets, sensors and catalysts. Thulium ion is an excellent blue activator and plays an important role in the design of persistent luminescent materials. This paper reports the investigation of the structural and luminescent properties of Barium Thulium Molybdate (Ba1?xTmx)MoO4 microcrystals (with x = 0, 0.01 or 0.03). The scheelite-type crystalline structure was identified from XRD and Raman studies. Under ultraviolet (359 nm) excitation, photoluminescence (PL) spectra present the characteristic emission bands at 453 nm and 545 nm which are due to the D12→F34 and D12→H34,5 transitions, respectively, from Tm3+ ions. Thermoluminescence (TL) measurements were performed with powdered samples previously irradiated with beta radiation. The depth of traps, associated with trap levels located inside the band-gap, was determined from TL data using different methods of glow curve analysis. The kinetic parameters, determined from thermoluminescent glow curves, provide evidence about a possible persistent luminescence emission from the (Ba0.97Tm0.03)MoO4 sample. This is a potential blue-light or ultraviolet long-lasting phosphor, with a trapping level lifetime, at room-temperature (300 K), of about 6 days.
- Marques, Ana Paula de Azevedo,Künzel, Roseli,Umisedo, Nancy K.,Latini, Renato Mazin,Yoshimura, Elizabeth Mateus,Okuno, Emico
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- Microstructure and spectroscopic properties of AMoO4 (A = Ca, Ba) particles synthesized via cyclic microwave-assisted metathetic route
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AMoO4 (A=Ca, Ba) particles have been successfully synthesized via cyclic microwave-assisted metathetic route in ethylene glycol followed by further heat-treatment. The AMoO4 (A=Ca, Ba) particles were well crystallized after heat-treatment at 400-600 °C for 3 h. The microstructures exhibited fine morphologies with sizes of 0.5-1 and 1.5-2 μm for the CaMoO4 and BaMoO4 particles, respectively. The synthesized AMoO4 (A=Ca, Ba) particles were characterized by X-ray diffraction, scanning electron microscopy. Other spectroscopic properties were also examined using photoluminescence emission measurements and Raman spectroscopy.
- Lim, Chang Sung
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- Synthesis and Luminescence Properties of a CsBaGd(MoO4)3:Er3+ Phosphor with a Scheelite-Like Structure
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A CsBaGd(MoO4)3:Er3+ phosphor with a scheelite-like structure (sp. gr. P21/n) has been synthesized and its luminescence properties have been studied. The synthesized material has been characterized by X-ray diffraction, differential thermal analysis, Raman spectroscopy, and IR spectroscopy.
- Kozhevnikova
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- Synthesis, structural and magnetic characterisation of the double perovskite A2MnMoO6 (A = Ba, Sr)
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A study of the crystallographic structure and magnetic properties of the double perovskites Ba2MnMoO6 and Sr2MnMoO 6 in polycrystalline form has been carried out by means of neutron powder diffraction (NPD) and magnetization measurements. The Rietveld analysis of room temperature data shows that the Mn2+ and Mo6+ ions are B-site ordered, i.e. the structure is a NaCl-type ordered double perovskite. Ba2MnMoO6 crystallizes in the cubic space group Fm3m (a = 8.1680(1)) and Sr2MnMoO6 crystallizes in the space group P42/n (a = 7.9575(5), c = 7.9583(9)). Bond valence sum (BVS) calculation revealed that these compounds have the valency pair of {Mn2+(3d5;t32ge2 g), Mo6+(4d0)}. The magnetic measurements suggest that these compounds transform to an antiferromagnetic state below 10 K.
- Azad,Eriksson,Ivanov,Mathieu,Svedlindh,Eriksen,Rundl?f
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- Bimetallic BaMoO4 nanoparticles for the C-S cross-coupling of thiols with haloarenes
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We disclosed new bimetallic BaMoO4 nanoparticles for the C-S cross-coupling reaction. The C-S cross-coupling reaction of alkyl/aryl thiols with haloarenes was accomplished with high yields. The reaction has good functional group tolerance and selectivity. This is an efficient protocol for synthesizing the building blocks of pharmaceuticals containing C-S bonds. The catalyst is recyclable. The unactivated bromo- and 4-acetyl fluoro-arenes can well couple to afford thioethers in high yields. The reaction is believed to proceed by oxidative addition and reductive elimination.
- Panda, Subhalaxmi,Sahu, Santosh Kumar,Behera, Pradyota Kumar,Panigrahi, Reba,Garnaik, Bamakanta,Rout, Laxmidhar
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supporting information
p. 2500 - 2504
(2020/02/20)
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- Insight into sulfamethoxazole degradation, mechanism, and pathways by AgBr-BaMoO4 composite photocatalyst
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A composite photocatalyst, AgBr-BaMoO4 was fabricated by two step method; microwave hydrothermal and precipitation-deposition. The as prepared photocatalyst samples were characterized by various techniques. The facet coupling was seen between the (204) plane of BaMoO4 and (200)/(222) planes of AgBr on the basis of XRD/HRTEM analysis. The pharmaceutical pollutant, sulfamethoxazole was adopted to investigate the photocatalytic performances of samples under UV–vis irradiation. The AgBr-BaMoO4 composite degraded the aqueous sulfamethoxazole drug in UV–vis light about 64% within 75 min, which was attributed to efficient separation of photogenerated electron–hole pairs across the interface between Ag/AgBr and BaMoO4. The multi-electron induced oxygen reduced reaction (ORR) was observed. The radical trapping experiment indicates that OH? has major role for sulfamethoxazole degradation. The four successive photodegradation of sulfamethoxazole in UV–vis light indicates the stability of composite photocatalyst. Furthermore, the three different degradation pathways were designed on the basis of retention time and molecular masses of 18 degraded organic fragments that was confirmed by high-performance liquid chromatography photodiode array (HPLC-PDA) and high resolution-quadruple time of flight electrospray ionization mass spectroscopy (HR-QTOF ESI/MS) techniques. The total organic carbon (TOC) analysis suggested the mineralization of SMZ by composite photocatalyst. This study not only demonstrates the enhancement of photocatalytic performance of wide band gap semiconductor by making composite with narrow band gap semiconductor but also detail degradation pathways and mechanisms of sulfamethoxazole.
- Ray, Schindra Kumar,Dhakal, Dipesh,Lee, Soo Wohn
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p. 686 - 695
(2018/07/14)
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- Incorporation of Europium(III) into Scheelite-Related Host Matrixes ABO4 (A = Ca2+, Sr2+, Ba2+ B = W6+, Mo6+): Role of A and B Sites on the Dopant Site Distribution and Photoluminescence
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Scheelite- and powellite-related materials doped with trivalent lanthanides or actinides have been the subject of extensive research due to their important role in mineralogical, technological, and environmental implications. Detailed structural knowledge of these solid solutions is essential for understanding their physicochemical properties and predicting material properties. In this work, we conduct a comprehensive spectroscopic analysis by means of polarization-dependent site-selective time-resolved laser-induced fluorescence spectroscopy, to delineate the influence of the host phase cations for a series of scheelite-type matrixes based on a general formula of ABO4 (A = Ca2+, Sr2+, Ba2+ B = W6+, Mo6+) on the local environment of the Eu3+ dopant. Eu3+ has been used as a luminescent probe to access the local structural environment of crystalline substitutional sites suitable for trivalent lanthanide or actinide occupation. Our results show that the lattice distortion is overall minor, but increases with increasing mismatch of host and guest cation size. We observe a linear dependence of Eu3+'s excitation energy on the host cation size and the A-O bond distance, which can be used to determine the hitherto unknown Eu-O bond distance in NaEu(WO4)2. A value of 2.510 ? was determined, somewhat larger than a previously reported number for NaEu(MoO4)2. The results also show clear evidence that the local coordination environment of Eu3+ in WO42- materials is more symmetrical than in their isostructural MoO42- counterparts. The detailed spectroscopic interpretation conducted in this study resolves the relation between local distortion around a dopant and the host phase cations in structural disordered materials and may give novel insights with respect to rational design and tailoring of functional materials.
- Xiao, Bin,Schmidt, Moritz
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p. 14948 - 14959
(2017/12/26)
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- Synthesis and luminescence properties of a Li3BaCaY3(MoO4)8:Er3+ phosphor with a layered scheelite-like structure
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A Li3BaCaY3(MoO4)8:Er3+ phosphor with a scheelite-like structure (sp. gr. C2/c) has been synthesized and its luminescence properties have been studied. The phosphor has been characterized by X-ray dif
- Kozhevnikova
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p. 419 - 423
(2017/04/06)
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- Enhancement of upconversion luminescence in BaMoO4: Er3+/Yb3+ microcrystals by the addition of KCl
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BaMoO4, co-doped with Er3+, Yb3+ and K+, microcrystals were synthesized by the microwave hydrothermal process. The crystal structure and particle morphology were investigated by X-ray diffraction (XRD) and scann
- Ray, Schindra Kumar,Adhikari, Rajesh,Joshi, Bhupendra,Gyawali, Gobinda,Kshetri, Yuwaraj K.,Regmi, Chhabilal,Tripathi, Khagendra,Lee, Soo Wohn
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p. 11173 - 11179
(2016/11/02)
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- Preparation of 2,3-diarylthiazolidin-4-one derivatives using barium molybdate nanopowders
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Barium molybdate (BaMoO4) nanopowder was successfully synthesized via a simple precipitation route without any surfactant. The prepared nanopowder was applied for the facile synthesis of 2,3-diarylthiazolidin-4-one derivatives using cyclization
- Taghrir, Hadi,Ghashang, Majid
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p. 246 - 250
(2015/10/12)
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- A study on the thermal conversion of scheelite-type ABO4 into perovskite-type AB(O,N)3
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Phase-pure scheelite AMoO4 and AWO4 (A = Ba, Sr, Ca) were thermally treated under an ammonia atmosphere at 400 to 900°C. SrMoO4 and SrWO4 were shown to convert into cubic perovskite SrMoO2N and SrWO1.5N1.5, at 700°C and 900°C respectively, and to form metastable intermediate phases (scheelite SrMoO4-xNx and SrWO4-xNx), as revealed by X-ray diffraction (XRD), elemental analysis and FTIR spectroscopy. High-temperature oxide melt solution calorimetry reveals that the enthalpy of formation for SrM(O,N)3 (M = Mo, W) perovskites is less negative than that of the corresponding scheelite oxides, though the conversion of the scheelite oxides into perovskite oxynitrides is thermodynamically favorable at moderate temperatures. The reaction of BaMO4 with ammonia leads to the formation of rhombohedral Ba3M2(O,N)8 and the corresponding binary metal nitrides Mo3N2 and W4.6N4; similar behavior was observed for CaMO4, which converted upon ammonolysis into individual oxides and nitrides. Thus, BaMO4 and CaMO4 were shown to not provide access to perovskite oxynitrides. The influence of the starting scheelite oxide precursor, the structure distortion and the degree of covalency of the B-site-N bond are discussed within the context of the formability of perovskite oxynitrides.
- Li, Wenjie,Li, Duan,Gao, Xin,Gurlo, Aleksander,Zander, Stefan,Jones, Philip,Navrotsky, Alexandra,Shen, Zhijian,Riedel, Ralf,Ionescu, Emanuel
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p. 8238 - 8246
(2015/05/13)
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- Aqueous sol-gel synthesis and thermoanalytical study of the alkaline earth molybdate precursors
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The preparation and characterization of the M-Mo-O nitrate-tartrate (M = Mg, Ca, Sr, and Ba) gels, which were produced by the simple aqueous sol-gel method and calcined at 500, 600, 700, 800, 900, and 1,000 °C temperatures are reported. The crystalline al
- Braziulis, Gediminas,Janulevicius, Gytautas,Stankeviciute, Ruta,Zalga, Arturas
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p. 613 - 621
(2015/01/09)
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- Coexistence of localized and itinerant electrons in the double-perovskite Ba2Fe2/3Mo4/3O6
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A polycrystalline Ba2Fe2/3Mo4/3O 6 double-perovskite has been prepared by decomposition of citrate precursors and subsequent thermal treatment under a reducing atmosphere. The crystal structure has been studied by combined X-ray and neutron powder diffraction (XRPD and NPD). At room temperature, the structure is cubic (Fm3?m) with lattice parameter a = 8.0710(1) ?. It is unchanged between 3 and 320 K. The crystallographic formula is Ba2[Fe 0.52(2)Mo0.48(2)]4a[Fe0.14(2)Mo 0.86(2)]4bO5.9(2). NPD, electron spin resonance (ESR), and magnetization measurements show spontaneous magnetization below the Curie temperature (TC) = 310 K. The ESR behavior is associated with the presence of localized Fe3+ ions, whereas the transport properties (electrical conductivity and Seebeck effect) suggest the presence of highly correlated electrons in a metallic band with disorder, which can be associated with the Mo t2g electrons. The coexistence of localized and itinerant electrons leads to non-negligible magnetoresistance properties.
- L?pez, Carlos A.,Saleta, Martín E.,Pedregosa, José C.,Sánchez, Rodolfo D.,Alonso, José A.,Fernández-Díaz, María T.
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p. 3555 - 3563
(2014/08/18)
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- Coexistence of localized and itinerant electrons in the double-perovskite Ba2Fe2/3Mo4/3O6
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A polycrystalline Ba2Fe2/3Mo4/3O6 double-perovskite has been prepared by decomposition of citrate precursors and subsequent thermal treatment under a reducing atmosphere. The crystal structure has been studied by combined X-ray and neutron powder diffraction (XRPD and NPD). At room temperature, the structure is cubic (Fmbar {3}m) with lattice parameter a = 8.0710(1) ?. It is unchanged between 3 and 320 K. The crystallographic formula is Ba2[Fe0.52(2)Mo0.48(2)]4a[Fe0.14(2)Mo0.86(2)]4bO5.9(2). NPD, electron spin resonance (ESR), and magnetization measurements show spontaneous magnetization below the Curie temperature (TC) = 310 K. The ESR behavior is associated with the presence of localized Fe3+ ions, whereas the transport properties (electrical conductivity and Seebeck effect) suggest the presence of highly correlated electrons in a metallic band with disorder, which can be associated with the Mo t2g electrons. The coexistence of localized and itinerant electrons leads to non-negligible magnetoresistance properties. A double-perovskite Ba2Fe2/3Mo4/3O6 with Fe/Mo (1:2 ratio) mixed valence states was obtained. From a synthesis under reducing conditions we have stabilized the coexistence of itinerant (associated with Mo) and localized (associated with Fe) electrons. This coexistence of electrons leads to non-negligible magnetoresistance properties.
- L?pez, Carlos A.,Saleta, Martín E.,Pedregosa, José C.,Sánchez, Rodolfo D.,Alonso, José A.,Fernández-Díaz, María T.
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p. 3555 - 3563
(2015/04/27)
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- Synthesis and electrical properties of ternary molybdates Li 3Ba2R3(MoO4)8 (R = La-Lu, Y)
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X-ray diffraction and differential-thermal analyses were used to study the phase relations in the subsolidus region of the system Li2MoO 4-BaMoO4-R2(MoO4)3. The temperature dependence of th
- Kozhevnikova,Kopylova
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p. 384 - 387
(2011/09/13)
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- Synthesis and X-ray diffraction and IR spectroscopy studies of ternary molybdates Li3Ba2R3(MoO4) 8 (R = La-Lu, Y)
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Ternary molybdates Li3Ba2R3(MoO 4)8 (R = La-Lu, Y) were synthesized by the solid-phase method. Their unit cell parameters were determined and IR spectra were assigned. The compounds are isostructural
- Kozhevnikova,Kopylova
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p. 935 - 938
(2012/03/12)
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- Phase formation in Li2MoO4-K2MoO 4-MMoO4 (M = Ca, Pb, Ba) systems and the crystal structure of α-KLiMoO4
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Solid-phase interactions in Li2MoO4-K 2MoO4-MMoO4 (M = Ca, Pb, Ba) systems were studied, and the subsolidus regions of these systems were triangulated. The lead and barium systems were studied in a more detailed way to discover that, along KLiMoO4-K2M(MoO4)2 (M = Pb, Ba), KLiMoO4-PbMoO4, and Li2MoO4-K 2Ba(MoO4)2 quasi-binary sections, there are homogeneity regions reaching 6-11 mol % based on K2M(MoO 4)2 and lead molybdate. Triple molybdates are formed in none of the systems, which is verified by experiments on spontaneous crystallization from solution in melt. Crystallization experiments yielded crystals of potassium dimolybdate and simple and double molybdates from the boundary systems. The crystal structure was solved for a hexagonal KLiMoO 4 phase: (Na,K){ZnPO4}, a = 18.8838(7) ?, c = 8.9911(6)?, Z = 24, space group P63, R = 0.065. The structure comprises a three-dimensional tridymite framework built by an alternation of corner-sharing LiO4- and MoO4 tetrahedra wherein voids are occupied by potassium cations.
- Gudkova,Solodovnikova,Solodovnikov,Zolotova,Kurat'Eva
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p. 1443 - 1452
(2011/12/13)
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- Synthesis and study of Li3BaSrR3(MoO 4)8 compounds (R = La-Lu, Y) with stratified sheelite structure
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Possibility of substituting barium ions with strontium ions in the stratified sheelite structure of Li3Ba2R 3(MoO4)8 (sp. gr. C2/c) was examined. The molybdates Li3BaSrR3(MoOsub
- Kozhevnikova,Kopylova
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p. 1498 - 1501
(2012/01/14)
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