Luminescence spectra and crystal structure of high-temperature superconductors

The luminescence spectra are obtained in the visible region for the high-T _c superconductors La₂CuO₄, YBA₂Cu₃O_7−δ , Bi₂Sr₂CaCu₂O_8±δ , and YBa₂Cu₃O_8±δ and for the secondary phases BaCuO_2±γ and Y₂Cu₂O₅. The presence of a luminescence band with energy E _lum∼2.4 eV in the spectra of all the investigated compounds is established. The nature of the observed luminescence bands is discussed on the basis of a comparative analysis of the crystal structures and luminescence spectra and on the basis of notions as to the presence of bands in the spectra accompanied by photoinduced diffusion of weakly bound oxygen and photoinduced charge transfer in the CuO₂ planes. Fiz. Tverd. Tela (St. Petersburg) 39, 1739–1746 (October 1997)