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Synthesis of LnMoO4-type molybdates for the entire rare earths row was carried out in a vacuum furnace at 1400 degree(s)C during 20 hours using Ln2MoO6 and MoO2. The obtained molybdates in the Ladivided byNd row crystallize in cubic syngony, europium molybdate EuMoO4--in tetragonal syngony, LnMoO4 molybdates for Sm, Gddivided byLu, Y--in monoclinic symmetry. LnMoO4-type molybdates are stable up to 210 - 270 degree(s)C. The main oxidation occurs at 600 degree(s)C. Investigation of interaction processes between LnMoO4 and chlorine was carried out using a special- purpose set-up. Our results show that LnMoO4 interaction with chlorine occurs in 600 - 750 degree(s)C temperature range. The obtained rare earth oxochloromolybdates are close in their structure to that of gadolinium oxochlorotungstate GdWO4Cl, and crystallize in monoclinic syngony. The decomposition process of TR oxochloromolybdates begins at 600 degree(s)C. Interaction of LnMoO4 (Ln equals La, Nd, Gd, Dy, Er) with sulphur was studied at 600 and 1000 degree(s)C. The ratio LnMoO4:S was 1:1. The specimen of GdMoO4+S composition is homogeneous and has scheelite-type structure with unit cell parameters a equals 5.2023 angstroms, c equals 11.1960 angstroms. Increasing of quenching temperature for LnMoO4 with S up to 1000 degree(s)C leads to the description of primary crystal structure of molybdates.
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