7789-82-4Relevant articles and documents
Chemical vapour transport of ternary oxides in the systems Ca/Mo/O and Sr/Mo/O
Steiner, Udo,Reichelt, Werner
, p. 1257 - 1266 (2006)
The chemical vapour transport behaviour of ternary phases in the Ca/Mo/O and Sr/Mo/O systems has been investigated using Cl2 as transport agent in a temperature gradient 1423 to 1323 K. MMoO4 (M= Ca, Sr) migrate in the above-mentioned temperature gradient with rates of 0.1 to 0.2 mg/h. Starting from three phase mixtures crystals of the compounds MMo 5O8 have been grown (migration rates: M = Ca 0.1 mg/h, M = Sr 0.01 mg/h). The observed transport behaviour is compared with predictions given by thermo dynamical model calculations and the influences of source composition and the moisture contents are described in detail.
Photophysical and photocatalytic properties of Ca1-xBi xvxMo1-xO4 solid solutions
Yao, Weifeng,Ye, Jinhua
, p. 11188 - 11195 (2006)
New solid solutions with the composition of Ca1-xBi xVxMo1-xO4 prepared by a solid-state method were found as novel photocatalysts with enhanced activity for O 2 evolution from aqueous solu
Preparation, characterization and photoluminescence of nanocrystalline calcium molybdate
Phuruangrat, Anukorn,Thongtem, Titipun,Thongtem, Somchai
, p. 568 - 572 (2009)
Nanocrystalline calcium molybdate was successfully synthesized from Ca(NO3)2 and Na2MoO4 in ethylene glycol using a microwave radiation method. Body-centered tetragonal structured calcium molybdate with narrow n
Influence of SO42? anionic group substitution on the enhanced photoluminescence behaviour of red emitting CaMoO4:Eu3+ phosphor
Balakrishna, A.,Letswalo, M. L. A.,Ntwaeaborwa, O. M.,Reddy, L.,Swart, H. C.
, (2021)
CaMoO4:xEu3+(x = 0.5, 1.0, 1.5, 2.0, and 2.5) powder phosphors incorporating SO42? anions were synthesized at high temperature using the solid-state reaction technique. The structural, morphological and optical properties of these phosphors were analysed using X-ray diffraction (XRD), field emission scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and optical spectroscopy. The XRD results indicate that the incorporation of SO42? anions and Eu3+ dopant ions did not affect the crystal structure of the CaMoO4, but largely influenced the luminescence properties of the CaMoO4–SO4:Eu3+ phosphors.The optical properties of our materials were examined using the UV–vis absorption spectroscopy. The absorption edges of the phosphors with different concentrations of Eu3+ were less than the band gap energy of the CaMoO4 and their values ranged from 3.30 to 4.75 eV. The intensity of the red photoluminescence (PL) from CaMoO4:Eu3+ phosphors was enhanced considerably upon incorporation of SO42? anions, suggesting that SO42? acted to capture primary excitation energy and transfer it non-radiatively to Eu3+ ions. In addition, the incorporation of SO42? ions also improved the fluorescence decay life-time values of the CaMoO4:xEu3+ phosphors significantly. Tunable emission was observed when the Eu3+ concentration was varied. Our PL results indicated that the CaMoO4–SO4:Eu3+ phosphor exhibited the highest red emission intensity compared to CaMoO4: Eu3+ phosphors, suggesting that CaMoO4–SO4:Eu3+ could be a promising red component material for potential application in white light-emitting diode devices.
Photoluminescent properties of phosphors in the system Ca xCd1-xMoO4:Eu3+, Li+
Wang, Jiaguo,Jing, Xiping,Yan, Chunhua,Lin, Jianhua,Liao, Fuhui
, p. G534-G536 (2005)
The luminescent properties of the new red phosphors in the solid solution system CaxCd1-xMoO4:Eu3+, Li + are reported. Their dominating emission peaks are at 615 nm, which satisfies color purity. Under the excitation of ～ 320 nm UV light, some selected samples have luminescent intensity 30% higher than that of the commercial red phosphor Y2O2S:Eu3+. Therefore, it is a promising material for N2 plasma display application.
Structural, lattice vibrational, optical and microwave dielectric studies on Ca1-xSrxMoO4 ceramics with scheelite structure
Ramarao,Kiran, S. Roopas,Murthy
, p. 71 - 79 (2014)
Structural, optical and microwave dielectric properties of Ca 1-xSrxMoO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) compositions were studied with help of Rietveld refinement and Raman spectroscopy measurements. All these compositions were prepared by solid state reaction method and observed to possess tetragonal scheelite structure with I41/a space group. Microwave dielectric properties such as dielectric constant (εr), quality factor (Q×f) and temperature coefficient of resonant frequency (τf) were measured using Hakki-Coleman method, reflection technique and invar cavity attached to hot plate respectively. εr, (Q × f) and τf are correlated with molar volume (Vm), MoO bond strength and Raman shift of A1g mode respectively. All these compounds show good microwave dielectric properties (εr = 6.7-9.6, Q × f = 35,000-52,000 GHz and τf = -28 to -17 ppm/°C). Band gap of these compositions was observed in the range 3.3-3.5 eV and variation in band gap was fitted with Bowing equation.
High temperature crystal chemistry and thermal expansion of synthetic powellite (CaMoO4): A high temperature X-ray diffraction (HT-XRD) study
Achary,Patwe,Mathews,Tyagi
, p. 774 - 781 (2006)
In this communication, the high temperature crystal chemistry of scheelite type (space group: I41/a) CaMoO4 (powellite) is reported. The details of the high temperature crystal structures were obtained by high temperature X-ray diffractometer (HT-XRD) data in the temperature range of 25-1000 °C. The lattice thermal expansions of this compound show the an-isotropic behavior, with the coefficient of thermal expansion along c-axis (αc) is almost double of that along the a-axis (αa). The average values of thermal expansion coefficient for CaMoO4 are: αa=13.5×10-6 and αc=22.8×10-6 °C. The typical thermal expansion behavior is basically controlled by the temperature-induced expansion of the Ca-O bonds, i.e. by the thermal expansion of the CaO8 polyhedra. The MoO4 polyhedra acts as typical rigid unit, with virtually no expansion. The preliminary data analysis for CaWO4 indicates almost similar values of thermal expansion coefficients, viz. αa=12.7×10-6 and αc=21. 4×10-6/°C (for CaWO4) in the same temperature range. The further details are explained in this manuscript.
Lassner, E.,Schlesinger, H.
, p. 195 - 198 (1957)
Synthesis and study of ternary molybdates RbCaR(MoO4)3 with a scheelite-like structure in Rb2MoO4–CaMoO4–R2(MoO4)3 systems (R = Nd, Sm, Eu, Gd)
Kozhevnikova
, p. 1518 - 1521 (2016)
Phase ratios in the subsolidus regions of Rb2MoO4–CaMoO4–R2(MoO4)3 systems (R = Nd, Sm, Eu, or Gd) were studied by vibrational spectroscopy, X-ray diffraction, and differential thermal analysis. Ternary molybdates RbCaR(MoO4)3 (R = Nd, Sm, Eu, Gd) with scheelite derivative structures (monoclinic symmetry system, space group P21/n) were synthesized. Unit cell parameters were determined, and IR and Raman spectra were characterized.
Structure-property relationships of novel microwave dielectric ceramics with low sintering temperatures: (Na0.5xBi0.5xCa 1-x)MoO4
Guo, Jing,Zhou, Di,Li, Yong,Shao, Tao,Qi, Ze-Ming,Jin, Biao-Bing,Wang, Hong
, p. 11888 - 11896 (2014)
A novel series of microwave dielectric ceramics (Na0.5xBi 0.5xCa1-x)MoO4 (0 ≤ x ≤ 0.6) was synthesized by the solid state reaction method. The crystal structures, microstructures, dielectric responses, and vibrational properties were investigated using X-ray diffraction, scanning electron microscopy, a microwave network analyzer, and terahertz, Raman and infrared spectroscopies. All the samples could be sintered well below 850 °C and a scheelite solid solution could be formed without any secondary phase. At x = 0.5 and x = 0.6, low-firing (750-775 °C) high performance microwave dielectric materials were obtained with permittivities of 19.1-21.9, Q × f values of 20,660-22,700 GHz, and near-zero temperature coefficients. The factors affecting microwave dielectric properties were discussed based on the vibrational data. As revealed by Raman spectroscopy, the disorder degree grows with x rising, which might increase the permittivities and decrease the Q × f values. The infrared spectra were analyzed using the classical harmonic oscillator model, and the complex dielectric responses gained from the fits were extrapolated down to the microwave and THz range. It is believed that the external vibration modes located at low frequencies dominate the main dielectric polarization contributions, especially the Na-O/Bi-O translational mode. This result indicates that the microwave dielectric properties of (Na0.5xBi 0.5xCa1-x)MoO4 ceramics mainly depend on the behavior of AO8 polyhedra. This journal is the Partner Organisations 2014.
Synthesis and electrical properties of scheelite Ca1-xSm xMoO4+δ solid electrolyte ceramics
Cheng, Jihai,Liu, Chenfei,Cao, Wenbing,Qi, Mingxing,Shao, Guoquan
, p. 185 - 189 (2011)
Scheelite-type Ca1-xSmxMoO4+δ electrolyte powders were prepared by the sol-gel auto-combustion process. The crystal structure of the samples was determined by employing the techniques of X-ray diffraction (XRD). According to the XRD analysis, the formed continuous series of Ca1-xSmxMoO4+δ (0 ≤ x ≤ 0.3) solid solutions had the structure of tetragonal scheelite, and the lattice parameters increased with increasing x in the Sm-substituted system. Results of sinterability and electrochemical testing revealed that the performances of Sm-doped calcium molybdate were superior to that of pure CaMoO4. Ca1-xSmxMoO4+δ ceramics show higher sinterability, and the Ca0.8Sm0.2MoO4+δ sample with 98.7% of the theoretical density were obtained after being sintered at 1250 °C for 4 h. The conductivity increased with increasing samarium content, and a total conductivity 9.54 × 10-3 S cm-1 at 800 °C could be obtained in Ca0.8Sm0.2MoO 4+δ sintered at 1250 °C for 4 h.
Microwave dielectric properties of the (1?x)La(Nb0.9V0.1)O4-xCaMoO4 (0.05?≤?x?≤?0.50) scheelite solid solution ceramics
Ma, Zhili,Zhao, Jinxiong,Zhou, Di
, p. 345 - 350 (2019)
The CaMoO4 was added into La(Nb0.9V0.1)O4 ceramics by solid state reaction method to adjust the temperature coefficient of frequency (TCF) values. The series of (1?x)La(Nb0.9V0.1)O4-xCaMoO4 (0.05 ≤ x ≤ 0.5) ceramics were sintered at 1060–1180 °C and found to possess permittivity (εr) = 10.38–17.73, Q × f = 31,820–76,570 GHz (Q = 1/dielectric loss, f = resonant frequency lying between 8.5 and 9 GHz), and TCF = ?26.3 ～ +160.7 ppm/°C. The structures of ceramic samples changed from monoclinic fergusonite to tetragonal scheelite continuously at x = 0.20 along with the shift of TCF values from positive to negative. The best microwave dielectric properties with εr = 15.71, Q × f = 76,310 GHz (at 8.825 GHz), and TCF = ? 26.3 ppm/°C were obtained in 0.8La(Nb0.9V0.1)O4-0.2CaMoO4 ceramics sintered at 1160 °C and these ceramics might be good candidates for microwave devices.
LUMINESCENCE OF CALCIUM MOLYBDATE.
Groenink,Hakfoort,Blasse
, p. 329 - 336 (1979)
Two emission bands are observed, one in the green and another in the orange spectral region. The shorter wavelength emission band is assigned to the **3T//1 yields **1A//1 transition in the tetrahedral molybdate group. The longer wavelength band is ascribed to a similar transition in a molybdate group lacking an oxygen ion, i. e. a MoO//3 group. Similar observations are made in the case of calcium tungstate.
Excitation spectra and luminescence decay analysis of K+ compensated Dy3+ doped CaMoO4 phosphors
Dutta,Som,Sharma
, p. 7380 - 7387 (2015)
A series of Dy3+/K+ doped calcium molybdate phosphors were synthesized by a hydrothermal synthesis method and structural, photoluminescence and decay studies were carried out. The crystal structure and phase of the prepared phosphors were investigated using X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). These studies show that the phosphors are of a tetragonal structure with a nanorod morphology. The photoluminescence results indicate that these phosphors could be efficiently excited by near-ultraviolet radiation which causes emission in the blue and yellow regions. A novel approach was used to calculate different spectral parameters of powder samples using excitation spectra instead of conventional absorption spectra. Quantitative calculation of spectral parameters, luminescence decay and quantum yield suggest the suitability of this phosphor as an efficient luminescent medium for light emitting devices.
The disordered cluster compound CaMo5(Mo0.38Ti 0.62)O10
Gougeon,Gall
, p. i30-i32 (2008)
The title compound, calcium penta-molybdenum titanium deca-oxide, is isomorphous with the AMo5(Ti0.7Mo0.3)O10 (A = Sr and Eu) compounds. The smaller size of calcium induces a higher molybdenum content on the capping sites of the bioctahedral Mo10 clusters, leading to more Mo11 and Mo12 clusters in the crystal structure. The oxygen framework derives from the stacking of close-packed layers along the a direction in the ABAC sequence. The Ca 2+ ions occupy large cavities which result from the fusion of two cubo-octahedra and are surrounded by ten O atoms. The Ti4+ ion is octa-hedrally coordinated by the O atoms.
Luminescence and photometric characterization of K+ compensated CaMoO4:Dy3+ nanophosphors
Dutta,Som,Sharma
, p. 9654 - 9661 (2013)
A series of CaMoO4 phosphors doped with trivalent dysprosium (Dy3+) and codoped with potassium (K+) ions were prepared by hydrothermal method. The nanostructures of the as-synthesized phosphors were investigated by X-ray diffraction (XRD). The results reveal that the obtained powder phosphors are single-phase scheelite structure with tetragonal symmetry and the crystallite size is in the range of 10-60 nm. The emission spectra show a bright yellow emission at 576 nm and blue emission at 487 nm. As a charge compensator, K+ ions were incorporated into CaMoO4:Dy 3+ phosphors, which enhance the PL intensities depending on the doping concentration of K+. The CIE parameters such as colour coordinates, colour correlated temperature and luminous efficacy of radiation were calculated using spectral energy distribution functions and McCamy's empirical formula. Photometric characterization indicates the suitability of K+ compensated CaMoO4:Dy3+ phosphor for white LED applications. The Royal Society of Chemistry 2013.
Traditional salt-in-water electrolyte: Vs. water-in-salt electrolyte with binary metal oxide for symmetric supercapacitors: Capacitive vs. faradaic
Appadoo, Dominique,Sundaram, Manickam Minakshi
, p. 11743 - 11755 (2020/09/09)
The electrochemical energy storage of lithium and sodium ions from aqueous solutions in binary metal oxides is of great interest for renewable energy storage applications. Binary metal oxides are of interest for aqueous energy storage due to their better structural stability and electronic conductivity and tunability of redox potentials. They have also been widely studied as novel electrodes for supercapacitors. The interactions between water and lithium/sodium ions, and water and binary metal oxide surface determine the electrochemical reactions and their long-term stability. Our results indicate that the aqueous sodium electrolyte has a stronger influence on the capacitance and cycling stability of the binary (Ca and Mo) metal oxide electrode than its lithium cousin. The symmetric cell in a two-electrode configuration was assembled with the proposed binary metal oxide, which shows an average discharge voltage of 1.2 V, delivering a specific capacitance of 72 F g-1 at a specific energy density of 32 W h kg-1 based on the total mass of the active materials. The development of highly concentrated aqueous electrolytes such as the water-in-salt electrolyte showed a larger electrochemical (voltage) window with enhanced storage capacitance for increasing the salt concentrations has also been discussed.
