High-pressure x-ray study ofCu2O andAg2O

Abstract

Pressure-induced phase transitions have been found in ${\mathrm{Cu}}_2$O and ${\mathrm{Ag}}_2$O by high-pressure x-ray diffraction technique at room temperature. ${\mathrm{Cu}}_2$O transforms from the cuprite to a hexagonal structure at a pressure of 10 GPa. This hexagonal form changes in the pressure range from 13 to 18 GPa into another hexagonal form, with a Cd${\mathrm{Cl}}_2$-type structure. Up to 24 GPa, the highest pressure generated, no decomposition of ${\mathrm{Cu}}_2$O into Cu and CuO was observed. ${\mathrm{Ag}}_2$O transforms at 0.4 GPa from the cuprite structure to a hexagonal structure which is identical with that found above 10 GPa in ${\mathrm{Cu}}_2$O. Extended $p-T$ phase diagrams of ${\mathrm{Cu}}_2$O and ${\mathrm{Ag}}_2$O are presented using the results of the x-ray study and, in the case of ${\mathrm{Cu}}_2$O, additional results of an optical investigation.