Phase relations in the systems Na2OIrO2 and Na2OPtO2 in air

The equilibrium phase relations for the Na₂OIrO₂ and Na₂OPtO₂ systems were determined in air using the quenching technique. The Na₂OIrO₂ system contains two stable compounds Na₂O·IrO₂ and 2Na₂O·3IrO₂, which dissociate at 1235 and 1040°C, respectively. The Na₂OPtO₂ system contains three compounds: Na₂O·PtO₂, metastable 2Na₂O·3PtO₂, and Na_xPt₃O₄ (0 ? x ? 1). Their dissociation temperatures are 890, 710, and 810°C, respectively. Indexed X-ray diffraction powder patterns for Na₂O·IrO₂ and 2Na₂O·3IrO₂ are given.