EXAFS AND XANES STUDY OF STRUCTURAL AND ELECTRONIC CHANGES IN Y1-XPRXBA2CU3O7

We present X-ray absorption fine structure (EXAFS) data from Y,Pr,Ba a nd Cu edges for various concentrations of Pr in Y1-xPrxBa2Cu3O7. Analy sis of Y K-edge EXAFS shows no evidence for major changes in interatom ic distance or in its mean square variation with composition. The indi vidual Ba-O distances have weak compositional dependence. The Pr-O dis tance is found to vary linearly with composition. We have interpreted the changes in Pr-O distance to conclude the existence of pr in a mixt ure of Pr3+ and Pr4+ states. The Cu-O coordinates at about 2.4 Angstro m, (the apical oxygen for Cu) appear to have a compositional dependenc e. Changes in electronic structure are also discussed besides structur al changes along with their correlation.