Structure determination of LISICON solid solutions by powder neutron diffraction

The structures of Li₃Zn_0.5GeO₄ and Li_3.5Zn_0.25GeO₄ have been determined by powder neutron diffraction studies at room temperature. Both compounds are members (x = 0.5, x = 0.75) of the LISICON solid solution series Li_(2+2x)Zn_(1-x)GeO₄ where -0.36 = x = 0.87. The structures, which are essentially similar, have been solved in the orthorhombic space group Pnma (No. 62) with cell dimensions a = 10.8720(5), b = 6.2882(3), and c = 5.1696(2) Å for Li₃Zn_0.5GeO₄ and a = 10.8845(7), b = 6.2683(4), and c = 5.1551(2) Å for Li_3.5Zn_0.25GeO₄; Z = 4. The basic structure of both compounds consists of an oxide ion array that is intermediate between hexagonal close packing and tetragonal packing, with Ge, Zn, and Li located in tetrahedral sites between the oxide ions. Additional Li is located in octahedral interstices which share faces with adjacent tetrahedral sites: Li ions in these tetrahedral sites are repelled through their faces to more distant tetrahedral sites. © 1988.