Revised phase diagram of Li2MoO4–ZnMoO4 system, crystal structure and crystal growth of lithium zinc molybdate

Orthorhombic lithium zinc molybdate was first chosen and explored as a candidate for double beta decay experiments with 100Mo. The phase equilibria in the system Li2MoO4–ZnMoO4 were reinvestigated, the intermediate compound Li2Zn2(MoO4)3 of the α-Cu3Fe4(VO4)6 (lyonsite) type was found to be nonstoichiometric: Li2−2xZn2+x(MoO4)3 (0≤x≤0.28) at 600 °C. The eutectic point corresponds to 650 °C and 23 mol% ZnMoO4, the peritectic point is at 885 °C and 67 mol% ZnMoO4. Single crystals of the compound were prepared by spontaneous crystallization from the melts and fluxes. In the structures of four Li2−2xZn2+x(MoO4)3 crystals (x=0; 0.03; 0.21; 0.23), the cationic sites in the face-shared octahedral columns were found to be partially filled and responsible for the compound nonstoichiometry. It was first showed that with increasing the x value and the number of vacancies in M3 site, the average M3–O distance grows and the lithium content in this site decreases almost linearly. Using the low-thermal-gradient Czochralski technique, optically homogeneous large crystals of lithium zinc molybdate were grown and their optical, luminescent and scintillating properties were explored.

The phase diagram of the system Li2MoO4–ZnMoO4 was revised, Li2−2xZn2+x(MoO4)3 (0≤x≤0.28 at 600 °C) isotypical to α-Cu3Fe4(VO4)6 was found. Structural studies for x=0; 0.03; 0.21; 0.23 show consecutive increasing the number of vacancies and atomic displacement anisotropy in the face-shared octahedral columns. Large Li2Zn2(MoO4)3 crystals were grown and their optical, luminescent and scintillating properties were explored.Figure optionsDownload as PowerPoint slide