Stoichiometry, structures and polymorphism of spinel-like phases, Li1.33xZn2 – 2xTi1 + 0.67xO4

Abstract

A complete range of spinel-like solid solutions forms between Li₄Ti₅O₁₂ and Zn₂TiO₄. Over a range of intermediate compositions, Li_1.33xZn_{2 – 2x}Ti_{1 + 0.67x}O₄(0.50 ⩽ x ⩽ 0.90), the solid solutions are primitive cubic, but for compositions to either side, they are face centred. Rietveld refinement of powder X-ray diffraction data shows that ordering of Li and Ti onto two sets of octahedral sites is responsible for the primitive structure; Li and Zn are disordered over the tetrahedral sites. A fully ordered, ideal composition occurs at x = 0.75, Li₂ZnTi₃O₈, which is isostructural with LiFe₅O₈. The phase diagram of the spinel join shows that the ordered, primitive cubic solid solutions transform to disordered, face-centred cubic solid solutions at high temperatures, with a maximum in the transition temperature at 1150 °C for x = 0.75. The subsolidus phase diagram Li₂TiO₃–TiO₂–ZnO at 1150 °C has been determined.