GASEOUS OXYGEN AT HIGH-PRESSURE AND ITS INTERACTION WITH CUPRIC OXIDE

Powder samples of CuO have been heat treated in gaseous O2 at temperat ures from 673 to 973 K an gas pressures up to 3000 atm using high-temp erature, metal pressure cells. Samples have also been run in a higher- pressure ''belt'' apparatus using KClO3 as the source of oxygen. The C uO incorporates excess oxygen up to about 2% but no higher oxides such as Cu3O4 or Cu2O3 or CuO2 were found. The excess oxygen in CuO may be present as peroxide ions. These produce only small effects on the ele ctrical properties of CuO. Some experiments of a similar nature were m ade on Cu2Y2O5 which accommodates more excess oxygen. These results ar e discussed as a function of both oxygen pressure and oxygen fugacity. Since no previous correlations of oxygen pressure and fugacity were a vailable, this study presents such plots. A pressure-temperature-densi ty plot for solid and fluid oxgyen is given up to 170 000 atm, 1300 K, and 2.6 g/cm-3 from which oxygen fugacities have been calculated. Com parisons of the present results with previous work on NiO, ZnO, and La 2CuO, are also given.