MICROSTRUCTURAL DEVELOPMENT AND ELECTRICAL-PROPERTIES OF SINTERED AND ANNEALED BISRCACU2OX

Samples of nominal composition BiSrCaCu2Ox were sintered and subsequently annealed. Differential thermal analysis (DTA) runs on calcined powders were used to determine the sintering temperature. Following sintering at 875-degrees-C the samples exhibit a multiphase microstructure, the matrix phase consisting of Bi2Sr2CaCu2Ox and Bi2Sr2Ca2Cu3Ox with a volume fraction of about 80%. The resistivity vs. temperature of the sintered samples shows a small drop at 110 K and a non-vanishing residual resistivity below 70 K. Additional annealing of these samples at 860-degrees-C results in a resistivity drop at 110 K and vanishing resistivity below 100 K. The critical current density initially increased with increasing annealing time and then became smaller for longer annealing times. This behaviour is explained by changes of internal interfaces caused by the postsinter annealing treatment.