Phase Equilibrium in Y–Ba–O System

In order to make clear the phase equilibrium in the Y–Ba–O system, the samples were prepared using the raw materials of Y2O3 and BaCO3 or BaO2 in natural air or in mixed gas of 21%O2+Ar, respectively. The phase relation was investigated using X-ray diffraction and EPMA methods. The carbon content was measured by means of oxygen combustion infrared absorption method. From the experimental results, the isobaric sections of the Y–Ba–O system were evaluated. Four compounds were found to exist in the air when using BaCO3 or BaO2 as one of the raw materials and also when using BaCO3 in a mixed gas of 21%O2+Ar. However, two of them, Y2Ba3O6·CO2 and Y2Ba4O7·CO2, were oxycarbonates. On the other hand, by sintering the raw materials of BaO2 and Y2O3 in the mixed gas of 21%O2+Ar, only two pure oxides, Y2BaO4 and Y4Ba3O9, were detected.