Degradation of properties of YBa2Cu3O(x) superconductors sintered in CO2-containing atmosphere.

摘要

Stability of the YBa(sub 2)Cu(sub 3)O(sub x) (YBCO) superconductor toward reacting with CO(sub 2) in CO(sub 2)/O(sub 2) gas mixtures during sintering was investigated as a function of the partial pressure of CO(sub 2) and temperature. The transport critical current density, J(sub c), of the superconductor decreased drastically with increasing partial pressure of CO(sub 2) was increased, J(sub c) became zero (at 77 K) even though the major phase of the sample was still a superconductor as determined by magnetic susceptibility measurements. Microstructures and compositions of the samples were investigated by transmission electron microscopy in conjunction with energy-dispersive x-ray spectroscopy. Two types of grain boundaries were observed: (approximately)10% of the grain boundaries contained a second phase; the regions near the remaining grain boundaries were tetragonal. At high partial pressures of CO(sub 2), the YBCO completely decomposed to BaCO(sub 3), Y(sub 2)BaCuO(sub 5), and CuO. 11 refs., 3 figs.