We present a detailed investigation of the bulk electronic properties of Y 1−x Pr x Ba 2 Cu 3 O 7 ͑YPrBCO͒ using x-ray absorption spectroscopy in the partial fluorescence yield mode ͑PFY-XAS͒ at Pr L 3 , Ba L 3 , and Cu K edges together with Pr 2p 3/2 3d 5/2 and Cu 1s2p resonant inelastic x-ray scatterings. Pr L 3 PFY-XAS spectra show that Pr is in the mixed-valence state ͑with the valence number slightly greater than 3͒ for the whole x = 0.2-1 range, while the Pr valence decreases with increasing x. The decrease of the Pr 4+ component upon Pr doping, hinting at a weakening Pr-O hybridization, is inconsistent with the scenario according to which the increase in Pr-O hybridization quenches the superconductivity in YPrBCO for x ജ 0.6. It rather suggests that the superconductivity may be suppressed by the total increase of the Pr-related states in the electronic structure due to the Pr ion concentration upon doping. No doping dependence is found in the electronic structure of the Ba and Cu sites, consistent with their invariant environment. No temperature dependence in our data is observed within the experimental accuracy.

x-ray emission in LiNbO 3 is confirmed by thermal treatments in a vacuum system by a new cleaning method of the crystal. Detailed single-crystal high-temperature x-ray structure refinements were carried out at 297, 323, 373, 423 and 473 K, far below the phase transition (∼1473 K). The unit cell dimensions a and V show a linear increase with temperature; however, the lattice parameter, c shows only a slight linear increase. The length of Nb-O bonds in adjacent octahedra is almost constant below 423 K. It is suggested that the valence electron in Nb changes in the compound. Therefore, x-ray emission induced by charged particles including electrons can be considered to have a close relation to the electric charge of Nb in LiNbO 3 .

No abstract