A complete range of spinel-like solid solutions forms between Li,Ti,O,, and Zn,TiO,. Over a range of intermediate compositions, Li, 33xZn2 -2xTil + o 6 7 x 0 4 (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, Li,ZnTi,O,, which is isostructural with LiFe,O,. 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 11 50 "C for x = 0.75. The subsolidus phase diagram Li,Ti0,-Ti02-Zn0 at 1150 "C has been determined.Conflicting reports on the occurrence of spinel-like phases in the system Li,O-ZnO-TiO, have appeared. The two endmember phases, Li,Ti,O,, and Zn2Ti04, are well established as spinels.'.2 In the system ZnO-TiO,, a range of spinel-like solid solutions is reported to form between Zn,Ti04 and ZnTiO, at temperatures below about 900"C;3 it has been suggested that instead of a solid solution, a second spinel-like phase with a defective structure, Zn2Ti,0s, forms4 but also that Zn2Ti,0, is in fact, a low-temperature polymorph of ZnTiO, .5 Spinel solid solutions are reported between Zn,Ti04 and Li4Ti5012, with a change in lattice type from face-centred to primitive cubic with increasing Li4Ti5012 content.6 Spinel phases have been reported with the formulae Li,ZnTi,O, and Li,Zn,Ti,0,,,7 both of which lie on the spinel join, Zn2Ti04-Li4Ti5012, but also with the composition Li,ZnTi,O,,, which lies to the Ti0,-rich side of the spinel join.' In addition, an area of spinel-like solid solutions between Zn,TiO,, ZnTiO, and Li,ZnTi,O, has been reported.6 Whilst Zn,TiO, was generally regarded as a cubic, inverse spinel with Ti,Zn disorder over octahedral sites, prolonged annealing at low temperatures led to a tetragonally distorted structure with octahedral siteWe have carried out a phase diagram study of the system Li,O-ZnO-TiO, in order to resolve the formula(e) of the ternary spinel-like phases and to understand the nature of the face-centred to primitive transition.
