AGING OF FRESH AND USED CA-SR-CUPRATE-BASED CATALYSTS

An ageing degeneration process was observed in a Ca-Sr-cuprate catalys t, both unused and after use in an NO decomposition reaction. The form ation of strongly interacting dipoles (SIDs) by Cu2+ and oxygen ions p erturbs the layerlike structure, which is typical of Sr3Cu5O8 species and is also characteristic of the present catalyst when it is fresh. T his phenomenon was observed with both unused and used aged samples. Fu rthermore, in the case of the used catalysts, the degeneration process lead to the disappearance of both the layerlike crystal structure and of the SID systems. However, the samples recover their properties whe n recalcined.