7787-37-3Relevant academic research and scientific papers
Report of the Double-Molybdate Phase Cs2Ba(MoO4)2with a Palmierite Structure and Its Thermodynamic Characterization
Colineau, Eric,De Zoete, Nathan,Griveau, Jean-Christophe,Rutten, Maikel,Smith, Anna L.,Van Eijck, Lambert
, p. 13162 - 13173 (2020)
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.
Structural and Thermodynamic Investigation of the Perovskite Ba2NaMoO5.5
Bou?xière, Daniel,Clavier, Nicolas,Epifano, Enrica,Guéneau, Christine,Kauric, Guilhem,Martin, Philippe M.,Smith, Anna L.,Van Eijck, Lambert
, (2020)
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
Synthesis, crystal structure and TEM study of the new hollandite-type Ba～8/7Mo8O16
Barrier,Gougeon,Retoux
, p. 120 - 126 (2001)
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-□-....
Structural and electrical properties of double perovskite: (BaSr)FeMoO6
Choudhary, R. N. P.,Das, Rutuparna
, (2021)
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.
HEATS OF FORMATION OF SOME SODIUM AND BARIUM VANADATES AND MOLYBDATES.
Kubaschewski,Hoster,Schlim
, p. 367 - 369 (1981)
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
Photoluminescence properties of BaMoO4 amorphous thin films
Marques, Ana Paula Azevedo,De Melo, Dulce M.A.,Longo, Elson,Paskocimas, Carlos A.,Pizani, Paulo S.,Leite, Edson R.
, p. 2346 - 2353 (2005)
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.
Formation of periodic precipitation patterns: A moving boundary problem
George, Jacob,Varghese, George
, p. 8 - 12 (2002)
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.
Thermal stability of alkali and alkaline-earth substituted LAMOX oxide-ion conductors
Selmi,Galven,Corbel,Lacorre
, p. 93 - 102 (2010)
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.
Novel carbon and sulfur-tolerant anode material FeNi3?PrBa(Fe,Ni)1.9Mo0.1O5+:δ for intermediate temperature solid oxide fuel cells
Xue, Shuangshuang,Shi, Nai,Wan, Yanhong,Xu, Zheqiang,Huan, Daoming,Zhang, Shaowei,Xia, Changrong,Peng, Ranran,Lu, Yalin
, p. 21783 - 21793 (2019)
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.
New microwave dielectric ceramics BaLn2(MoO4) 4 (Ln = Nd and Sm) with low loss
Zhou, Di,Pang, Li-Xia,Guo, Jing,Wu, Ying,Zhang, Gao-Qun,Dai, Wei,Wang, Hong,Yao, Xi
, p. 2800 - 2803 (2011)
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
