The effects of anneal time and cooling rate on the formation and texture of Bi2Sr2CaCu2O8 films

The effects of anneal time and cooling rate on the formation and texturing of superconducting Bi₂Sr₂CaCu₂O₈ (BSCCO) films were investigated. Samples were prepared by sputter-depositing amorphous BSCCO films, annealing them at 870°C in flowing 20% O₂-80% Ar for 30, 60, or 180 min, and then cooling them. Two cooling rates were investigated: a fast cool of 80°C/min and a slow cool of 9°C/min. It was observed that effective coupling between superconducting 2212 grains occurs when films exhibit a minimum amount of (00l) texturing. The nucleation and growth kinetics are significantly different for the isothermal and cooling regimes of thermal processing. Consequently, anneal time and cooling rate play distinct roles in the achievement of the appropriate texture and microstructure in the films: longer anneal times increase the volume fraction of the 2212 phase, while slower cooling rates enhance grain growth and texturing. The mechanism by which 2212 grains are coupled within a film is not well understood. It is suggested that grain growth mechanisms and rates may determine the extent of coupling between grains