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[en] Methods of X-ray diffraction, electron-microscopic, X-ray spectrometric and electron-diffraction analysis were used to study CdWO₄ crystals, grown by Czochralski method from charge with different ratio of CdO and WO₃ oxides under positive oxygen pressure of 150 kPa. It is shown that a new phase is separated under growing of CdWO₄ crystals, due to deviation of their composition from stoichiometric one. This phase is precipitated on walls of pores in crystrals. Precipitation composition is determined by the ratio of CdO and WO₃ oxides in initial charge. It was establishet that a new phase was not precipitated in thge absence of pore formation during crystal growing

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[en] The crystal structure of TR₂WO₆ oxytungstates was determined for TR--Ho-Lu and Y taking Y₂WO₆ and Yb₂WO₆ as examples (sp. gr. P2/c, Z=4, R=4.5 and 2.9%, respectively). Three-dimensional skeleton is formed of polyhedrons WO₆(octahedrons), TR1O₈ and TR2O₈ (antiprisms) and TR3O₇ (single-cap trigonal prisms). The presence of rather perfect fluorite-like cation frame is typical

[en] Polarized Raman spectra have been obtained on oriented single crystals of Ag₈W₄O₁₆ from 20⁰C to the melting point (620⁰C) and also of the melt, both in air and in an oxygen atmosphere. The temperature dependences of the low-frequency Ag⁺-ion vibrations show no anomalies, in contrast to those in ionic conductors such as α-AgI. Polarization versus temperature measurements have been made on the crystals under the same conditions as the Raman measurements. The results indicate that there is decomposition of the crystals in air which produces irreversible conducting phases. The oxygen atmosphere impedes this decomposition, and the results in this case confirm an earlier prediction that there is no crystallographic transformation of the crystals up to the melting point and that the (W₄O₁₆)^8- ions continue to be noncentrosymmetric in the melt

[en] Cation positions in 20 structural types of double molybdates and tungstates with mono- and trivalent metals representing more than 300 structures of compounds of this class are analysed. Cation accumulation near crystallographic planes with d_hkl=2.9-3.7 A is characteristic for most of them, that gives evidence about high density of cation population in these planes with minimum inter-cation contacts 3.5-4.5 A. A regular sublattice with individual order of cation population in the nodes for each compound can be detected in the most popular case (15 structures) in the cation matrix. Such cation matrices are call linear. In three structural types analogous cation matrix is divided into layers connected by microtwinning or crystallographic shift operations (linear-block cation matrices)

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[en] The systems Ag₂WO₄-Sc₂(WO₄)₃ and Ag₂WO₄-In₂(WO₄)₃ have been explored by using the methods of the differential-thermal, X-ray phase, and infrared-spectroscopy analyses. The consititutional diagrams for these systems have been constructed. In the systems indicated, there form compounds with the component ratio 1:1, which show incongruent melting: AgSc(WO₄)₂ Melts at 695 deg C, whereas AgIn(WO₄)₂, at 93 deg C, these binary compounds undergoing polymorphic transformations at 660 deg C and 890 deg C, respectively. Their eutectic compositions in both cases contain approximately 1 mole % of trivalent metal tungstate and melt at a temperature of 590 deg C