ELECTRON-BEAM-INDUCED COMPOSITIONAL AND STRUCTURAL-CHANGES IN TL2BA2CUO6+DELTA

Tl2Ba2CuO6+delta ceramics have been irradiated in a scanning electron microscope. The resultant changes in the cationic stoichiometry and ox ygen content of the samples were investigated by cathodoluminescence ( CL), secondary electron emission (SEE) and EDX microanalysis. ii deple tion and Ba enrichment are observed in the irradiated areas. CL spectr oscopy shows that irradiation causes the increase of a 540 nm emission band attributed to complex centres involving oxygen vacancies. Other features of the CL spectra strongly suggest the presence of radiation induced new phases. The SEE yield, Delta, has been found to depend on the oxygen content of the samples This dependence can be explained on the basis of two charge carrier subsystems and their mutual interactio n, Measurements of Delta allow us to detect an oxygen deficient region , sometimes extending up to a distance of about 1000 mu m, that surrou nds the irradiated material.