13451-05-3Relevant articles and documents
Synthesis, structures and temperature-induced phase transitions of the Sr2Cd1-xCaxWO6 (0 ≤ x ≤ 1) double perovskite tungsten oxides
Faik,Igartua,Pizarro
, p. 196 - 201 (2009)
The solid solution with double perovskite structure and general chemical formula Sr2Cd1-xCaxWO6 (0 ≤ x ≤ 1) has been synthesized by the co-precipitation method. The Cd2+ cation substitution by Ca
Well-defined strontium tungstate hierarchical microspheres: Synthesis and photoluminescence properties
Jia, Guang,Huang, Cuimiao,Zhang, Cuimiao,Ding, Shiwen,Wang, Liyong
, p. 611 - 616 (2013)
Uniform and well-dispersed SrWO4 microspheres have been successfully synthesized through a hydrothermal method by using trisodium citrate and SDS as surfactants. XRD and SEM results demonstrate that the as-synthesized SrWO4 particles are high purity well crystallized and exhibit a relatively uniform spherical morphology. The as-obtained SrWO 4:Ln3+ (Ln = Tb, Eu, Dy, and Sm) microspheres show intense light emissions with different colors coming from different Ln3+ ions under ultraviolet excitation, which might find potential applications in the fields such as light emitting phosphors, advanced flat panel displays, and light-emitting diodes (LEDs). Copyright
Controllable synthesis of hierarchical nanostructures of CaWO4 and SrWO4 via a facile low-temperature route
Chen,Gong,Zhu,Yuan,Qian,Qian
, p. 45 - 50 (2009)
CaWO4 and SrWO4 nanostructures have been synthesized via a simple microemulsion-mediated route. With careful control of the fundamental experimental parameters including the concentration of reactants, the reaction time and the tempe
Structural and thermal investigations of Sr2WO5
Keskar, Meera,Sali,Vats,Phatak,Krishnan,Kannan
, p. 3639 - 3647 (2017)
The crystal structure of Sr2WO5has been refined using powder X-Ray diffraction (XRD) and neutron diffraction (ND) data. The corner connected WO6octahedra forms infinite cis-bridged chains along b axis which are further connected by the layer of Sr atoms to give a three dimensional network. Thermogravimetric study revealed that Sr2WO5on storage picks up moisture from the surrounding to give a mixture of Sr(OH)2and SrWO4. Percentage of Sr(OH)2in Sr2WO5increases with increase of storage time under normal atmospheric condition. The hydrated compound on heating up to 1473?K again yield back Sr2WO5. High Temperature X-ray Diffraction (HTXRD) studies of Sr2WO5and SrWO4in vacuum showed positive thermal expansion in the temperature range of 298–1273?K. Thermogram of Sr2WO5recorded with Differential Scanning Calorimeter (DSC) showed a reversible phase transition at 423?K. Specific heat capacity of Sr2WO5was measured between temperature 463–863?K using heat flux DSC.
Raman studies of A2MWO6 tungstate double perovskites
Andrews,Heyns,Woodward
, p. 10700 - 10707 (2015)
The Raman spectra of seven A2MWO6 tungstate double perovskites are analysed. Ba2MgWO6 is a cubic double perovskite with Fm3m symmetry and its Raman spectrum contain three modes that can be assigned in a straightforward manner. A fourth mode, the asymmetric stretch of the [WO6]6- octahedron, is too weak to be observed. The symmetry of Ba2CaWO6 is lowered to tetragonal I4/m due to octahedral tilting, but the distortion is sufficiently subtle that the extra bands predicted to appear in the Raman spectrum are not observed. The remaining five compounds have additional octahedral tilts that lower the symmetry to monoclinic P21/n. The further reduction of symmetry leads to the appearance of additional lattice modes involving translations of the A-site cations and librations of the octahedra. Comparing the Raman spectra of fourteen different A2MWO6 tungstate double perovskites shows that the frequency of the symmetric stretch (ν1) of the [WO6]6- octahedron is relatively low for cubic perovskites with tolerance factors greater than one due to underbonding of the tungsten and/or M cation. The frequency of this mode increases rapidly as the tolerance factor drops below one, before decreasing gradually as the octahedral tilting gets larger. The frequency of the oxygen bending mode (ν5) is shown to be dependent on the mass of the A-site cation due to coupling of the internal bending mode with external A-site cation translation modes.
Room-temperature preparation of crystallized luminescent Sr1-xCaxWO4 solid-solution films by an electrochemical method
Cho, Woo-Seok,Yashima, Masatomo,Kakihana, Masato,Kudo, Akihiko,Sakata, Tadayoshi,Yoshimura, Masahiro
, p. 137 - 139 (1996)
A complete series of well-crystallized solid-solution oxide films, Sr1-XCaXWO4 (0≤X≤1), has been prepared on a tungsten substrate in the electrolytic solution containing Sr2+ and Ca2+ ions by an electrochemical method at room temperature (25°C). The composition of solid-solution oxide films could easily be controlled by the concentrations of Sr and Ca species in the starting solutions. The films showed only single blue emission at liquid nitrogen temperature (-196°C), strongly suggesting that they consisted of well-crystallized defect-free crystals.
Effect of MWO4 (M = Ca, Sr, Ba) dispersion on the interfacial processes in (+/-)WO3|MWO4|WO3(-/+) cells and transport properties of metacomposite phases
Pestereva,Safonova,Nokhrin,Neiman
, p. 876 - 882 (2010)
We compare data on the reciprocal electrosurface transfer (EST) of WO 3 and MWO4 components through WO3|MWO 4 eutectic heterointerfaces using MWO4 (M = Ca, Sr, Ba) samples prepared by standard ceramic technology (CER) and nitrate-organic technology (N/O); these samples considerably differ in both the grain size of precursor powders and the grain size of sintered ceramics. When an electric field is applied, the interpenetration of WO3 and MWO4 components occurs though WO3|MWO4 (M = Ca, Sr, Ba) heterointerfaces. The general(-)WO3 MWO4(+) intermigration pattern in the cells is not influenced by tungstate preparation technology. However, interpenetration rates are far greater forMWO 4N/O. The transport properties of {MWO4 ·xWO3} two-phase eutectic metacomposites manufactured by both technologies were studied. Tungstate and composite manufacturing technologies have no radical influence on the electric properties (overall and partial conductivity, transference numbers) of the samples, only changing conductivity versus concentration relationships. Our data well fit the model of formation of a nonautonomous electrolytic inter-phase. Pleiades Publishing, Ltd., 2010.
PREPARATION OF CUBIC PEROVSKITES A(B2/5W3/5)O3 (A equals Ba OR Sr, B equals Na OR Li).
Hikichi,Suzuki
, p. c. 99-c. 100 (1987)
Pure cubic perovskites Ba(Na//2/////5W//3/////5)O//3, Sr(Na//2/////5W//3/////5)O//3 were prepared by solid-state reaction at 600 degree to 650 degree C in air, by starting with oxides or carbonates of the various elements. The cubic forms have an ordered arrangement of the B cations in the ABO//3 structure.
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
Xiao, Bin,Schmidt, Moritz
, p. 14948 - 14959 (2017)
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.
Synthesis, characterization and novel photoluminescence of SrWO4:Ln3+ nanocrystals
Xu, Bingyu,Li, Mingxia,Pan, Kai,Li, Rong,Fan, Naiying,Wang, Guofeng
, p. 3522 - 3526 (2016)
SrWO4:Ln3+ (Ln = Eu, Ce, and Tb) nanocrystals were successfully synthesized by a hydrothermal method, and were characterized by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. The results indicated that the crystalline size of nanocrystals decreases with increasing Eu3+ concentrations and increases with increasing annealing temperature, gradually. The photoluminescence properties of SrWO4:Ln3+ were investigated in detail. In the emission spectra of SrWO4:Eu3+, the luminescence was dominated by 5D0 → 7F2 transition, indicating that Eu3+ occupied a site lacking inversion symmetry. The concentration quenching effect hardly occurs. In the excitation spectra of SrWO4:Eu3+ nanocrystals monitored at 619 nm, the most intense peak is centered at 467 nm when the Eu3+ concentration was less than 10%, while the most intense peak is centered at 396 nm when the Eu3+ concentration was 15%. In the normalized emission spectra of SrWO4:Ce3+/Tb3+ nanocrystals excited at 254 nm, the intensity ratio of the sharp emission peaks from Tb3+ ions to the broad emission band from Ce3+ ions increased with increasing Tb3+ concentration.
