Phase formation and grain growth kinetics of high-T-c superconducting Tl-1223 ceramics

The phase formation and grain growth of (Tl,Pb,Bi(Sr,Ba)(2)Ca2Cu3O9-delta ceramics were investigated in the temperature range between 860 degrees C and 1000 degrees C. It was found that partial melting seems to improve the texture of the samples. The phase purity, however, is limited due to an incomplete reprecipitation process due to the formation of a liquid phase, which is already present above 885 degrees C. The resulting grain growth exponent n, however, appears to differ from the classical exponent of 1/3 for the coexistence of a liquid phase in the temperature range between 885 degrees C and 920 degrees C. For the first time, the activation energy for the high-T-c Tl-1223 phase has been determined showing faster grain growth kinetics than for Y-123 and Bi-2223.