Several samples of PrBa2Cu3O0.67, Pr1+xBa2-xCu3O7-δ and La1+xBa2-xCu3O7-δ have been synthesized and examined by X-ray diffraction and polarized micro-Raman scattering. The X-ray diffraction refinement results on these samples show a decrease of the Cu(2)-O(4)-Cu(1) bond length due to partial Ba-site substitution by large radius RE-ions. The Raman scattering shows an increase of the apical O(4) stretching frequency in agreement with the structure data. The increasing of the O(4) vibration frequency with the rare-earth induced bond-length changes can account for previous seemingly contradictory Raman results on PrBa2Cu3O7. An empirical relation was found between the effective force constant k for O(4) and the Cu(1)-Cu(2) spacing d: k∝d-6. The oxygen disorder induced peak at ∼ 600 cm-1 is also discussed.
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