Structure and properties of antimony-doped lanthanum molybdate La2Mo2O9статья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Polycrystalline samples of the composition La2Mo2-xSbxO9-y, where 0 <= x <= 0.05, were prepared by solid-phase synthesis. Single crystals of La2Mo1.96Sb0.04O8.17 were obtained by spontaneous crystallization from flux. The structure of the metastable b(ms) phase of this compound was determined at room temperature by X-ray diffraction. It was found that the La, Mo, and O1 atoms are displaced from the threefold axis on which they are located in the high-temperature b phase. It was shown that molybdenum atoms in the crystal structure are partially replaced by antimony atoms, which are located on the threefold axis. In antimony-doped crystals, lanthanum atoms partially return to the site on the threefold axis and the coordination environment of molybdenum cations becomes more ordered, thus facilitating the stabilization of the cubic phase at room temperature. Calorimetric measurements (DSC) showed that the introduction of Sb as the dopant into the La2Mo2O9 structure leads to a decrease in the temperature of the a -> b phase transition from 570 to 520 C and to the partial suppression of this transition. The temperature behavior of the conductivity confirms the DSC data. Thus, doping with Sb contributes to the stabilization of the cubic phase at room temperature.