THE MICROSTRUCTURAL AND CRITICAL CURRENT PROPERTIES OF MELT-PROCESSED YBCO+AG THICK-FILMS

The eff ect of Ag addition on the microstructure and critical current properties of YBa2Cu3O7-x thick films is reported. A comparison between isothermally processed thick films of YBCO and YBCO + Ag2O revealed considerable differences in both surface morphology and internal microstructure. Addition of Ag reduces macroscopic cracking in the films and also reduces the extent of film/substrate reaction, thereby minimizing associated deviations from correct stoichiometry in the film. Evidence of a barium-copper-silver solution at high temperatures, which is thought to play an important role in the modification of microstructures obtained, and the decomposition temperatures of the phases involved are reported. A reduction in stability of several phases present in the Ag containing thick film precursor at high temperatures was determined using DTA. This included an approximate 30-degrees-C reduction of the YBa2Cu3O7-x phase formation and peritectic decomposition temperatures in an oxygen atmosphere. The addition of Ag increases the critical current densities of the films, realizing values of approximately 3000 A cm-2.