PHASE RELATION IN Y211-Y123-AG SYSTEM AND MORPHOLOGY OF SILVER IN Y123 CRYSTAL

Phase relation in the Y2BaCuO5 (Y211)- YBa2Cu3O7-x (Y123)-Ag system, w hich is important for the fabrication of Y123/silver composite, and th e morphology of silver particles dispersed in the Y123 matrix were inv estigated. The formation temperature of Y123 monotonously decreased to about 970 degrees C as increasing Ag content up to a pseudo-monotecti c composition and kept constant at the temperature with further Ag add ition. The Y123/silver composite could be obtained at the temperatures lower than 970 degrees C. These results suggest that Y123 phase is so lidified by monotecto-peritectic reaction; Y211 + L1 (Ba-Cu rich liqui d) = Y123 + L2 (Ag rich liquid). The morphology of silver particles in Y123 was altered by the addition of excess Y211. in the samples witho ut excess Y211, silver particles dispersed in Y123 were disk-like shap ed. On the other hand, those became spherical in the samples with exce ss Y211. The capturing mechanism of L2 liquid is considered to be the Uhlmann, Chalmers, and Jackson (UCJ) type pushing one. The amount of r esidual Y211 particles at the growth interface is considered to cause the morphological difference of captured silver between samples with a nd without excess Y211. (C) 1998 Elsevier Science B.V.