Preparation and Raman analysis of single-phase Y1−xPrxBa2Cu3O7−δ

Abstract

A series ${\mathrm{Y}}_{1-x}{\mathrm{Pr}}_x{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ materials with $0\le x\le 1$ have been prepared that do not show phase separation and have sharp superconducting transitions for $x\le 0.45$. These samples have been characterized by x-ray-diffraction, resistivity, field-cooled magnetization, and thermogravimetric analysis. Raman spectra have been obtained for the entire series, including the nonsuperconducting regions. The O(4) stretching mode at ∼500 ${\mathrm{cm}}^{-1\mathrm{}}$ is seen to harden by 15 ${\mathrm{cm}}^{-1\mathrm{}}$, while the Cu(2)-O(2,3) out-of-phase bending mode at ∼340 ${\mathrm{cm}}^{-1\mathrm{}}$ is seen to soften by 40 ${\mathrm{cm}}^{-1\mathrm{}}$ on going from Y${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ to Pr${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$. These changes fall on a universal curve for the Raman shifts of all the compounds $R{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_7$ ($R=\mathrm{rare}\mathrm{earth}$) as a function of the radii of the rare-earth ions. No abrupt changes in the Raman shifts are observed at $x=0.5\mathrm{}$, where the superconductivity is destroyed.