Local disorder in the oxygen environment around praseodymium in Y1-xPrxBa2Cu3O7 from x-ray-absorption fine structure.

PrBa2Cu3O7 (PBCO) is unique in the RBa2Cu3O7 (R=rare earth) series because it is not superconducting. In fact, for Y1−xPrxBa2Cu3O7, Tc drops monotonically with Pr concentration, with Tc going to zero at ∼55% Pr. There have been many studies of this material with the hope that an explanation for the lack of superconductivity in PBCO might help explain why YBa2Cu3O7 (YBCO) is superconducting. Explanations center around hole localization, requiring an extra hole on the Y (Pr) site or a localized hole in the O 2p shell, at the expense of a mobile hole in the Cu-O planes. To help provide clues that could point to a particular model, and to search for anomalies in the local structure, we present K-edge XAFS (X-Ray Absorption Fine Structure) data for various concentrations of Pr in Y1−xPrxBa2Cu3O7. The character of the Pr K-edge XAFS data indicate that most of the Pr substitutes onto the Y site and is well ordered with respect to the unit cell. These data also show that the amplitude of the first Pr-O peak is greatly reduced when compared to the first Y-O peak in pure YBCO, and decreases with increasing