DIFFERENCES BETWEEN THE FORMING PROCESSES OF RBA2CU3O7-X (R=Y, YB) PHASES AND PREPARATION OF THE SINGLE-PHASE YB-123 SUPERCONDUCTOR

The formation of YBa2Cu3O7-x(Y-123) and YbBa2Cu3O7-x(Yb123) phases, the synthesis of single-phase Yb-123, and the lowest temperature for obtaining the single-phase Y-123 superconductor have been studied by X-ray diffraction, differential thermal analysis, and superconductivity measurements. The results indicate that the Y-123 phase is formed from the principle chemical reaction Y2O3 + 4BaCO3 + 6CuO + (1 - 2x)/2O2 --> 2YBa2Cu3O7 - x + 4CO2 up The reactions for forming Yb-123 phase are Yb2O3 + BaCO3 + CUO --> Yb2BaCuO5 + CO2 BaCO3 + CuO --> BaCuO2 + CO2 up Yb2BaCuO5 + 3BaCuO2 + 2CuO + (I - 2x)/2O2 --> 2YbBa2Cu3O7-x. In our experiments, the lowest temperature for obtaining the near-single-phase Y-123 bulk superconductor is 780-degrees-C; a simple procedure for synthesis of the single-phase Yb-123 superconductor is described. (C) 1994 Academic Press, inc.