XANES and EXAFS study of (Tl0.5Pb0.5)Sr2(Ca1−xGdx)Cu2Oz superconductors

Results of X-ray absorption spectroscopy study on Gd doped (Tl0.5Pb0.5)Sr2(Ca1−xGdx)Cu2Oz. (x=0.1, 0.2 and 0.3) superconductors are reported. The Gd L3 absorption edges were studied in the XANES (near-edge) region and in the EXAFS (extended X-ray absorption) region. The XANES spectra are typical for Gd in oxide compounds with the absorption edge followed by a strong “white line” peak which slightly decreases its intensity with increasing Gd content x. The Fourier transformed EXAFS spectra reveal two well resolved peaks corresponding to the oxygen nearest neighbours and the cation next neighbour shell, respectively. From simulations and of the EXAFS spectra to the structure of the host 1212 compound the location site of gadolinium is determined and its possible influence on the local structural environment of the site is analyzed.

► EXAFS study of (Tl0.5Pb0.5)Sr2(Ca1−xGdx)Cu2Oz shows that Gd locates at the Ca site.
► Replacement of Ca by Ga does not cause lattice distortions.
► The location of Gd at the Ca sites does not deteriorate the superconducting properties.