Phase Relations in the System In₂O₃-TiO₂-Fe₂O₃at 1100°C in Air

Phase relations in the system In₂O₃-TiO₂-Fe₂O₃at 1100°C in air are determined by means of a classic quenching method. There exist In₂TiO₅, Fe₂TiO₅having a pseudo-Brookite-type phase and a new phase, In₃Ti₂FeO₁₀having a solid solution range from In₂O₃:TiO₂:Fe₂O₃=4:6:1 to In₂O₃:TiO₂:Fe₂O₃= 0.384:0.464:0.152 (mole ratio) on the line "InFeO₃"-"In₂Ti₂O ₇." The crystal structures of In₃Ti₂FeO₁₀are pyrochlore related witha_m=5.9171 (5) Å,b_m=3.3696 (3) Å,c_m=6.3885 (6) Å, andβ=108.02 (1)° in a monoclinic crystal system at 1100°C, anda₀=5.9089 (5) Å,b₀=3.3679 (3) Å, andc₀=12.130 (1) Å in an orthorhombic system at 1200°C. The relationship between the lattice constants of these phases and those of the cubic pyrochlore type are approximately as follows:a_m=-14a_p+(-12)b_p+(-14)c _p,b_m=-14a_p+(0)b_p+(14)c _p,c_m=14a_p+(-12)b_p+(14)c _pandβ=109.47° in the monoclinic system, anda₀=-14a_p+(-12)b_p+(-14)c_p,b ₀=-14a_p+(0)b_p+(14)c_p, andc₀=23a_p+(-23)b_p+(23)c_pin the orthorhombic system, wherea_p=b_p=c_p=9.90 (Å) are the lattice constants of "In₂Ti₂O₇" having the cubic pyrochlore type. All solid solutions of In₃Ti₂FeO₁₀have incommensurate structures with a periodicity ofq×b^*(q=0.281-0.356) along theb^*axis and the stoichiometric phase hasq=13. InFeO₃having a layered structure type is unstable between 750 and 1100°C.