Texture, strains, and superconductivity in Y1-xPrxBa2Cu3O7-δ

We investigate the Y1-xPrxBa2Cu3O7-delta (0 <= 1 x <= 1) and YBa2-yPryCu3O7-delta (y = 0.1 and 0.2) polycrystalline compounds via X-ray diffraction and Raman measurements. The oxygen concentration measurements show all samples to be optimally doped or overdoped. The magnetic measurements M(Y) and chi(ac)(T) verify that the increase of the Pr content leads to the expected strong systematic decrease of the critical temperature T-c and the suppression of superconductivity for x > 0.55. Systematic micro-Raman studies of the observed vibrational modes reveal a coexistence of locally different rare-earth seemingly nanoscopic environments in the mixed rare-earth Y123 systems that has been overlooked to a great extent up to now. The comparison of the Raman spectra from the two sets of compounds proves that an increased amount of Ba is occupied by Pr in Y1-xPrxBa2Cu3O7-delta and indicates that loss of superconductivity is mainly due to hole filling by this occupancy. (c) 2007 Elsevier B.V. All rights reserved.