The phase relations in the system In₂O₃-TiO₂-MgO at 1100 and 1350°C

The phase relations in the system In₂O₃-TiO₂-MgO at 1100 and 1350°C are determined by a classical quenching method. In this system, there are four pseudobinary compounds, In₂TiO₅, MgTi₂O₅ (pseudobrookite type), MgTiO₃ (ilmenite type), and Mg₂TiO₄ (spinel type) at 1100°C. At 1350°C, in addition to these compounds there exist a spinel-type solid solution Mg(2-x)In(2x)Ti(1-x)O₄ (0 ≤ x ≤ 1) and a compound In₆Ti₆MgO₂₂ with lattice constants a = 5.9236(7) Å, b = 3.3862(4) Å, c =6.3609(7) Å, β = 108.15(1)°, and q =0.369, which is isostrucrural with the monoclinic In₃Ti₂FeO₁₀ in the system In₂O₃-TiO₂-MgO. The relation between the lattice constants of the spinel phase and the composition nearly satisfies Vegard's law. In₆Ti₆MgO₂₂ extends a solid solution range to In₂₀Ti₁₇Mg₃O₆₇ with lattice constants of a = 5.9230(5) Å, b =3.3823(3) Å, c =6.3698(6) Å, β = 108.10(5)°, and q =0.360. The distributions of constituent cations in the solid solutions are discussed in terms of their ionic radius and site preference effect.(C) 2000 Academic Press.