Improved synthesis and characterization of the copper Lyonsite-type compound Cu4−xMo3O12

A novel method involving a molten Ga flux for the synthesis of diffraction quality crystals of the compound Cu3.82(1)Mo3O12, a copper molybdate in the Lyonsite (α-Cu3Fe4(VO4)6) family, has been developed. Single-crystal X-ray diffraction data have been collected. Cu3.82(1)Mo3O12 crystallizes in the space group P212121 with cell dimensions of a=4.9972(1) Å, b=11.0259(3) Å, and c=17.4912(5) Å. Refinement of the resulting structure has enabled modeling of disorder in the channels of the structure and has indicated the localization of copper vacancies to these channel positions. Thermopower measurements indicate that Cu3.82(1)Mo3O12 is a rare and interesting example of a cation-deficient n-type material.