酸化物超伝導体の結晶化学-(Y,La,Ba)3Cu3Oy擬3元系の合成と超伝導

概要

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Superconductig compounds of pseudo-ternary (Y, La, Ba)3Cu3Oy system were synthesized and crystallographic parameters and superconducting properties were measured. Compounds of YBa2-xLaxCu3Oy series were found to be single phase up to x=1 and orthorhombic to tetragonal transition at room temperature took place with x=0.5. Tc decreased with increasing x and superconductivity disappeared for x>0.6. These results can be interpreted to be due to the decrease in average valence of copper Ions from 2.33 of YBa2Cu3O7 with Increasing x, which was caused by the substitution of divalent Ba ions by trivalent La Ions. On the other hand complete solid solution was formed for Y1-xLaxBa2Cu3Oy series, where Tc decreased gradually with Increasing x. Considerable Increase In Tc was found for the La substituted specimens by annealing around 400°C for 24hrs.