Polarized Raman measurements of Y1-xPrxBa2Cu3O7.

We report polarized Raman measurements on small single crystals embedded in ${\mathrm{Y}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Pr}}_{\mathit{x}}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ polycrystalline pellets. The measurements show two-mode behavior in the Cu-O bending mode of the ${\mathrm{CuO}}_{2}$ planes (${\mathit{B}}_{1\mathit{g}}$ mode). The increase in frequency with x of the Ba-Ba stretching mode and the chain copper\char21{}apical oxygen Cu(1)-O(4) stretching mode is consistent with hole localization on Ba sites due to Ba 5d\char21{}O 2p covalency. This localization may be related to the suppression of superconductivity in this compound, which increases with increasing x.