Thermal decomposition of [R_2(H_2O)_(12)Mo_8O_(27)] centre dot H_2O (R= rare earth) at 700-800 deg C in air gave single crystals of novel R_2O_3:MoO_3 compounds with 1:6, 1:5, 1:4, 2:7, and 3:10 ratios. The crystallization, which occurred in the melt of the precursor, was enhanced by repeated use of the same alumina crucible. The preparation of 1:5 and 2:7 compounds can be achieved exclusively by this method, and that by usual solid state reactions has been unsuccessful. Structural details for some compounds are described in the presentation.
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