Direct Preparation of Fine Powders of the 80K Superconducting Phase in the Bi-Ca-Sr-Cu-O System by Spray Pyrolysis.

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The preparation of fine superconductive Bi_2Ca_1Sr_2Cu_2O_x particles by ultrasonic spray-pyrolysis technique verified the feasibility of controlling the properties of the final product particles by changing the temperature profile, initial concentration of corresponding metal nitrate solution and the flow rate. The experimental results shows that there exists the possibility of morphological control of superconductive particles generated from the evaporation and thermal decomposition of solution droplets.The body sintered from these powders at 840^ﾟC showed the offset of superconducting transition at TAU_c=104K. Furthermore, the thick films have been prepared on a Ag plate or between two Ag plates using the powders. The powders were pressed on a Ag plate or between two Ag plates at 200 kg/cm^2 and heat-treated at 855^ﾟ for 30 min. The resultant films on a Ag plate were again heat-treated at 840^ﾟC for 62 hr after the cooling to room temperature. The thick films obtained showed the offset temperature of 104K. On the other hand, the films sandwiched between Ag plates, which were heat-treated also at 855^ﾟC for 40 hr after the cooling, showed the offset temperature of 80K.