Investigations of oxygen diffusion in high temperature superconductors on the cuprate basis and of the degradation of YBa2Cu3O6+δ in oxygen atmospheres containing carbon dioxide and water

Interaction between ceramic high temperature superconductors (YBa2Cu3O6+δ and La2-xSrxCuO4±y) and atmospheric components (oxygen O2m carbondioxide CO2 and water H2O) were examined during the production process at high temperatures (900-1000 C) and during storage at room temperature. The reaction kinetics were determined by the methods of chemical diffusion and tracer diffusion. The diffusion of CO2 and H2O led to a decomposition reaction of the superconductor. Thin Ba(OH)2 and BaCO3 layers and other non-superconducting reaction products are formed on the sample surface. The growth of the reaction layer was controlled by the diffusion of carbon and water through the layer formed. In the further course of the reaction, there was a local decomposition reaction of the YBaCu3O6+δ and the formation of a complex layer system with very finely distributed phases. The diffusion coefficients of the water had the same order of magnitude as those of oxygen, while the diffusion coefficients of the carbon were two orders of magnitude smaller. (orig./MM)