Characterization of high Tc superconductor by luminescence methods

High-T_c superconductors have been investigated by photoluminescence (PL) and X-ray excited thermally stimulated luminescence (TSL) techniques. Characteristic PLs have been observed in the infrared region in the Er-Ba-Cu-O and Nd-Ba-Cu-O systems, which are tentatively assigned to electronic transitions between weakly crystal-field-split spin-orbit levels of trivalent Er and Nd ions. The spectral shapes and/or peak positions are dependent on the crystal arrangement surrounding the rare-earth ion. Such PLs have never been obtained in the Eu-Ba-Cu-O and Yb-Ba-Cu-O systems. TSL measurements have been performed with particular emphasis on the Gd-Ba-Cu-O system. Characteristic TSLs have been observed in this system, depending on the composition, preparation conditions and cumulative X-ray irradiation time. The activation energy of the related traps ranges from 0.1 eV to 0.3 eV. Characteristic TSLs have also been observed in the Ho-Ba-Cu-O and new high-T_c superconducting systems containing no rare-earth elements