Textured Thick Films of Bi2Sr2Ca1Cu2Ox

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Abstract
Thick textured films of Bi2Sr2Ca1Cu2O x are obtained by partially melting and slow cooling doctor-blade-processed tapes. Heat treatment between 890 and 870°C produces aligned microstructures on substrates of either Ag or Ag coated MgO. During heat treatment dissolution of Ag into the liquid oxide occurs. Because silver lowers the melting point of the oxide, the processing temperatures must be increased by about 10°C when an MgO substrate is used. The resulting films show that the oxide surface plays an important role in grain alignment. The Bi2Sr2Cu1O x phase, stable for temperatures greater than about 870°C, always transforms to the desired Bi2Sr2Ca1Cu2O x phase regardless of the heat treatment history (quenched from 890°C and annealed at 870°C or slowly cooled from 890°C to 870°C). The texture of the microstructure, however, is dependent upon the heat-treatment path, with a higher texture obtained with slower cooling.