Bi-Pb系酸化物高温超伝導体のHIP処理 (酸化物系超伝導物質と材料<特集>)

概要

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It is well known that HIP treatment provides highly densified ceramics. The influences of HIP treatment on the densification of the Bi-Pb high-Tc ceramics and the electrical conductivity have been studied on the sample with a nominal composition of Bi0.96Pb0.24Sr1.0Ca1.1Cu1.6Ox. It was found that the density of the sample was attained over 90% of the theoretical density of the Bi-Pb high-Tc phase by the HIP treatment at 850°C for 2h. While the electrical resistance of the sample without HIP treatment decreased in linear with decreasing temperature from 280K to 120K and dropped to zero near 100K within the experimental limit, that of the HIP treated sample increased semiconductively between the temperature range from 280K to 110K, and below 110K gradually dropped to zero at 60-70K. However, the degradation of the HIP treated sample in the electrical conductivity was recovered by the heat treatment at 850°C for 48h in air. This behavior in the electrical conductivity seems to be associated with the precipitation of Ca2PbO4 in the grain boundary and the deficient of oxygen in the high-Tc phase.
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