Influence of Sintering and Microstructure on the Superconductivity of YBa2Cu3Oy

Two kinds of YBa2Cu3Oy powders were cold pressed and sintered at 1073-1273K for 86.4ks; one is the mixed powders (M powders) and the other is the alloy powder (A powder) obtained by pulverizing the mixed powder aggregate fired at 1173K for 86.4ks, and the relation between the sintering behavior and superconducting properties were Investigated.The sintered density ratio of A specimen was higher than that of M specimen in any cases sintered at 1073-1273K, and the highest sintered density ratio of about 90% of theoretical was obtained in the A specimen sintered at 1253K for 86.4ks, whereas the highest zero resistance temperature of 94K was observed in the specimen sintered at 1173K for 86.4ks.The Cu rich phase other than YBa2Cu3Oy phase was detected in the M specimens sintered at 1223K and 1253K for 86.4ks, while in the A specimens sintered at the same temperatures, only YBa2Cu3Oy phase was observed.