CATHODOLUMINESCENCE MICROSCOPY OF SUPERCONDUCTING AND NONSUPERCONDUCTING TL2BA2CUO6+DELTA POLYCRYSTALS

Luminescence properties of Tl2Ba2CuO6+delta samples with different sup erconducting transition temperatures have been studied by cathodolumin escence (CL) in the scanning electron microscope. Independent of the c rystal structure, tetragonal or orthorhombic, the Cl spectra show two resolved bands at about 430 nm (2.9 eV) and 540 nm (2.3 eV), respectiv ely. The results show that the 2.3 eV emission is related to oxygen co ntent and is more intense in low-oxygen content superconducting sample s. It is proposed that this band is related to a complex center involv ing oxygen vacancies. A comparison of spectra from Tl2Ba2CuO6+delta an d from precursors used in the synthesis (CuOx, Tl2Ba2O5) has been carr ied out.