Luminescent properties of x-irradiated rare-earth-doped barium copper oxides

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Abstract
Thermally stimulated luminescence (TSL) of x-ray-induced defects in R-Ba–Cu–O (R = Gd, Ho, and Eu) has been measured. In the interval 25–400°C, Ho- and Eu-doped samples exhibit similar TSL with peaks at 65, 135, and 185°C. The GdBa2Cu3Ox has, in addition to the three aforementioned peaks, a maximum at 310°C. All TSL peaks are attributed to recombination of F+s – and F−s center electrons with Vs-type holes, requiring typical thermal activation energies 0.5–1.0 eV. Spectral emission data support this conclusion. Irreversible quenching of TSL is found to occur in each sample. It is postulated that adsorbed oxygen molecules interact with radiation-induced F+s and Fs centers to produce O−2 and O2−2 molecular ions, respectively, thereby reducing the surface oxygen vacancy concentration and quenching the luminescence. In addition to activation energies, other TSL parameters are extracted from the data. It is suggested that surface TSL in these oxide superconductors is independent of rare-earth dopant.