STRUCTURAL INVESTIGATION OF THE EUBA2CU3O7-DELTA HIGH-TC SUPERCONDUCTOR BY EU-151, SN-119, FE-57 AND CO-57 MOSSBAUER-SPECTROSCOPY

By introducing Eu-151, Sn-119, Fe-57 and Co-57 into the orthorhombic perovskite lattice of YBa2Cu3O7-delta high T(C) superconductors, the localization and distribution of these probe nuclides were investigated by Mossbauer spectroscopy in order to get further information on the structure of high T(C) superconductors. The Mossbauer spectra of superconductor samples were considered as superpositions of subspectra belonging to Mossbauer nuclides occupying different sites with various surroundings in the lattice. The Eu-151 spectra were evaluated as singlets corresponding to Eu(III) situated at the normal rare earth site. The Sn-119 spectra were decomposed into a singlet and a doublet, which were associated with Sn(IV) at the Cu(2) and the Cu(1) sites, respectively. The Fe-57 and Co-57 spectra could be fitted with three doublets representing Fe(III) and Fe(IV) at the Cu(1) site as well as Fe(III) at the Cu(2) site. Comparing the relative area fractions of Mossbauer lines corresponding to different Cu sites it was suggested that iron and cobalt prefer the Cu(1) site, while tin prefers the Cu(2) site in these superconductors.