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.

Date Published: 24 March 1999
PDF: 6 pages
Proc. SPIE 3724, International Conference on Solid State Crystals '98: Single Crystal Growth, Characterization, and Applications, (24 March 1999); doi: 10.1117/12.343006

Published in SPIE Proceedings Vol. 3724:
International Conference on Solid State Crystals '98: Single Crystal Growth, Characterization, and Applications
Andrzej Majchrowski; Jerzy Zielinski, Editor(s)