REAL STRUCTURE AND PHOTOLUMINESCENCE SPECTRA OF COPPER OXIDE HIGH-Tc SUPERCONDUCTOR SINGLE CRYSTALS AND CERAMICS. T.V.Smirnova and P.V.Zinoviev, B.Verkin Institute for Low Temperature Physics & Engineering, Kharkov, UA 310164, Ukraine

The present work is aimed at studying correlation between peculiarities of the real structure (RS) of HTSC and evolution of the photoluminescence spectra (PS) and establishing the nature of spectral bands of superconducting cuprates. PS of single crystals with different oxygen content and coarse-grained ceramics of YBa₂Cu₃O_7- have been studied. The oxygen index d in single crystals was defined by the Raman spectra and XRD. PS of single crystals with = 0.1 and = 0.9 in the blue-green region exhibit, in fact, a single band with a maximum in the vicinity of 2.8 eV, whereas those of single crystals with non-stoichiometric oxygen exhibit also the band with a maximum near 2.4 eV. In superconducting (T_c ~ 92 K) coarse-grained ceramics samples of YBa₂Cu3O_7- the main contribution to the PS is from the band with a maximum near 2.8 eV. The contribution from the band near 2.4 eV increases upon mechanical grinding and light exposure of the samples. The effect of RS and light exposure is associated with processes of the oxygen vacancies formation.