Thermal behavior of the Pb-substituted Bi-2223 phase was examined by characterizing samples annealed at 500°C to 850°C in air and also those subsequently reheated at 850°C in air by XRD, SEM and magnetic measurements. Very interesting reactions occurred, which were segregation of precipitates on annealing below 830°C and dissolution of the precipitates on subsequent reheating at 850°C into the 2223 phase. The precipitates were identified as Sr2.5Bi0.5Pb3Ca2CuO2. The precipitation and the dissolution were clearly confirmed by morphological observations of a fixed portion of a sample before and after heat treatments. These results strongly suggest that the 2223 phase changes its composition reversibly between the relatively Pb-rich composition stabilized above 850°C and relatively Pb-poor ones stabilized in essentially the same structure below 830°C. However, Tc remained almost constant at 113 K.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering