SUPERCONDUCTING PROPERTIES AND STRUCTURAL STABILITY OF BI2SR2CACU2O8+DELTA COMPOUND PREPARED BY ELECTROCHEMICAL REDUCTION IN PROTOGENIC ELECTROLYTE

Superconducting Bi2Sr2CaCu2O8+delta (Bi-2212) compound was electrochem ically reduced in a protogenic electrolyte of benzoic acid dissolved i n acetone. The critical temperatures (T-c) of the reduced Bi-2212 were enhanced from 75 K up to similar to 90 K, which were reportedly the h ighest value of Bi-2212 superconductor, In spite of the enhancement of T-c, a diamagnetism of Bi-2212 was weakened after the reduction. This phenomenon was discussed in terms of the flux penetration depth. The electrochemically reduced Bi-2212 had a different structural stability from a partly oxygen-removed Bi-2212 which was prepared by annealing in reducing atmospheres. These results are attributable to injection o f protons from the benzoic acid into the Bi-2212 structure.