CORROSION PROCESS OF BISMUTH-BASED SUPERCONDUCTOR CUPRATES IN A MOISTURE ATMOSPHERE

Sintered pellets and single crystals of Bi2Sr2CaCu2O8 (2212) and Bi2Sr 2CuO6 (2201) have been exposed to moistened air or just to water vapou r. The following alterations observed have been studied by SEM, microa nalysis, optical microscopic techniques, and FTIR. A possible reaction path for the alteration process is proposed. By means of optical and SEM observations, several morphologies of the alteration products have been observed. Two main steps, responsible for the degradation, have been found: the leaching of Sr and Ca cations from the matrix by fixed water, then a carbonate and hydroxide precipitation. In both cases, C a and Sr extraction leads to Bi2CuO4.