Electron-energy-loss spectroscopy has been used to investigate the changes of the electronic structure in ${\mathrm{Y}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Pr}}_{\mathit{x}}$${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ (0≤x≤1). The O 1s absorption edges and the low-energy-loss function indicate that Pr does not fill holes in the ${\mathrm{CuO}}_2$ planes. This suggests, by comparison with other experiments, that Pr localizes mobile holes thereby leading to the suppression of superconductivity and the metal-insulator transition.

• Received 22 May 1990

DOI:https://doi.org/10.1103/PhysRevB.42.4823