Phase Relations in the Systems TiO₂-IrO₂ and SnO₂-IrO₂ in Air

The pseudobinary systems TiO₂-IrO₂ and SnO₂-IrO₂ were studied by x-ray diffraction after treatment at various temperatures in air. Their equilibrium phase diagrams were similar, with no intermediate phases detected in either system. Maximum solid solution of TiO₂ occurs with the addition of about 5 mole percent IrO₂ at 1040 °C. Solid solution of TiO₂ in IrO₂ extends to a maximum of about 12 mole percent TiO₂ at 1040 °C, the dissociation temperature. Limited solid solubility of SnO₂ in IrO₂ exists up to 3 mole percent SnO₂ at the dissociation temperature, 1025 °C. Solid solution in SnO₂ was not detected at temperatures up to 1400 °C.