ON THE THERMODYNAMICS OF THE FORMATION OF YBA2CU3O7-X FROM TERNARY OXIDE PRECURSORS

Gibbs energy data on the formation of T2Cu2O 5, BaCuO2, Y2BaCuO5 (2-1-1 phase) and YBa2Cu3O7-x (1-2-3 phase) have been applied to assess the role of various oxide precursors in the method of synthesis of ceramic superconductors. Such an analysis upheld the validity of the 1223 K section of the phase diagram of the YO1.5-BaO-CuO system in air for the 1023 K section of this system in oxygen at 1 atmosphere, in the regions surrounding the 1-2-3 and 2-1-1 phases. The ternary precursors method using Y2Cu2O5 and BaCuO2 for the synthesis of 1-2-3 compounds appears to be more advantageous from a thermodynamic point of view in limiting the occurrence of the 2-1-1 phase than other methods.