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.