Compounds and Phase Relations in the SrO–CaO–CuO System under High Pressure

Abstract

The phase relation in the ternary SrO–CaO–CuO system under high pressure has been studied by means of powder X-ray diffraction, electron diffraction, and high-resolution electron microscopy. In the SrO–CuO system studied in a pressure and temperature range of 1.7–8 GPa and 850–1150°C, Sr 2CuO 3, SrCuO 2(II), Sr 2Cu 3O 5, and SrCu 2O 3form. In the CaO–CuO system, CaCuO 2(I) of the infinite-layer type forms at 3–5 GPa and 1050–1200°C. This compound undergoes a polymorphic structural transformation into another high-pressure form CaCuO 2(II) which comprises a new type of CuO 2planes. A structural model built on the basis of electron diffraction and high-resolution electron microscopy is presented. The ternary phase diagram at 4 GPa and 1020°C is presented.