部分溶融プロセスで作製したBi2212相厚膜の表面抵抗

抄録

Using a dielectric resonator method at 10.7GHz in the TE₀₁₁ mode, we investigated the microwave surface resistance (R_s) of screen-printed Bi₂Sr₂CaCu₂O_x (Bi2212) thick films on Ag substrate subjected to a partial-melt solidification process. Heat treatment conditions on the partial-melt solidification process influence the R_s value of thick films through changes in microstructures therein. We obtained a low R_s value of 1.6mΩ at 20K by heating the film up to a maximum temperature of 880°C, subsequent slow cooling at 4°C/h from 880 to 860°C, isothermal annealing for 10h at 860°C and final cooling to room temperature. To our knowledge, this R_s value is the lowest record for Bi2212 thick films subjected to the partial-melt solidification process. The factor dominating the R_s value of Bi2212 thick films was investigated from a microstructural point of view. The film with low R_s value shows a large grain size, small amount of impurity phases and also a high degree of grain alignment. A significant correlation between microstructures and R_s values of Bi2212 thick films was suggested.