Effect of oxide additions on the polymorphism of tantalum pentoxide. III. ""Stabilization"" of the low temperature structure type

The "low temperature structure type" of Ta2O5 has been found to occur in two distinct forms with the lowest temperature form having a unit cell 14 times the subcell and an intermediate temperature form with a unit cell 11 times the subcell. The two types form intermediate partially ordered mixtures which are apparently in thermal equilibrium at various temperatures between ~ 1000 and 1350 °C. The addition of MoO3, WO3, SiO2, GeO2, ZrO2, TiO2, B2O3 and Al2O3 each affect the multiplicity of the true unit cell in different ways. WO3, SiO2, GeO2, B2O3, and Al2O3 form phases structurally similar to "low-Ta2O5" which are stable up to the solidus temperatures of the corresponding systems.