Characterization of high T/sub c/ superconductor by luminescence methods

High T/sub c/ superconductors have been systematically investigated by photo- (PL) and x-ray excited thermally stimulated luminescence (TSL) techniques. In PL measurements, characteristic PLs have been observed in the infrared region of 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 significantly 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, which might reflect their band structures. 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 range from 0.1 eV to 0.3 eV. Characteristic TSLs have also been observed in the Ho-Ba-Cu-O and new high T/sub c/ superconducting systems including no rare-earth elements, e.g., Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O