STRUCTURAL AND COMPOSITION CHANGES IN SUPERCONDUCTING CERAMICS LOCALLY IRRADIATED BY ELECTRONS

The structural changes and the cation and anion compositions of the su rface of superconducting YBa2Cu3O7-x and Tl2Ba2CuO6+x ceramics after l ocal irradiation for several seconds by an electron probe with an acce lerating voltage of 25 kV and a current exceeding 10(-7) A are investi gated by secondary-electron emission and by cathodoluminescence and x- ray microanalysis in a scanning electron microscope, Morphologically a ltered regions are detected in the irradiation epicenter, where the st ructure, chemical composition, and phase composition of the original c ompound are completely lost. In the intermediate zone between the epic enter and the periphery a distribution of the secondary emission yield is observed with a complex character that differs for the yttrium and thallium ceramics, and anomalies appear in the cathodoluminescence sp ectra, The experimental data are interpreted on the basis of ideas of oxygen losses under the direct influence of the electron probe and rel ated electronic processes in superconductors. (C) 1997 American Instit ute of Physics.