Influence of the powder calcination temperature on the microstructure in Bi(Pb)-2223 tapes

One goal of our research is to be able to manufacture high temperature superconducting cables for power transmission. The key elements is the production of superconducting tapes using the oxide powder in tube process. If quality and critical current density of the tapes can be improved, the quality and capacity of the final cable will also be improved. In this work we have calcinated the powder used in the powder in tube process at different temperatures and the microstructure of ceramic phase has been studied after rolling and after two annealings. It is observed that the powder calcination temperature has a strong influence on the microstructure, that is the arrangement and growth of superconducting phases as well as the secondary phases. It is found that the amount of big secondary particles is lowest for calcination temperatures of 820-830/spl deg/. Better crystal growth and grain sintering during first and second annealing are also observed for these calcination temperatures.