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Published online by Cambridge University Press: 15 February 2011
In constrast to other rare earths, replacement of Y with Pr in the high Tc superconductor YBa2Cu3O7 has a pronounced effect on Tc, with Tc going to zero at ≈ 55% Pr. We present Pr XAFS K-edge data for various concentrations of Pr in Y1−xPrxBa2Cu3O7. The Pr K-edge data show that the amplitude of the first Pr-O peak is greatly reduced when compared to the first Y-O peak in pure YBa2Cu3O7. In constrast, for the Y K-edge data in these alloys, there is little if any change in the oxygen environment, while the Cu K-edge data show at most a 10% reduction in the first Cu-0 peak. Fits to the Pr data suggest either that oxygen atoms in the CuO2 planes are missing or that some oxygen atoms about the Pr become highly disordered. Either result could help explain the reduction of Tc with increasing concentration of Pr.