Mechanochemical effects of grinding on the Bi-Pb-Sr-Ca-Cu-O superconductor

The effects of mechanical grinding on the powder of the Bi-Pb-Sr-Ca-Cu-O superconductor (so-called 'high Tc phase') were examined. The grain size of the powders decreased with increased grinding time accompanied by the degradation of crystallinity. Powders involving relatively lower crystal strain recovered their crystallinity as 'high Tc phase' by postheat treatment. But powders having relatively excessive crystal strain recrystallized as 'low Tc phase' and others. Such an effect reveals the metastability of the high Tc phase under the condition of excessive crystal strain.