Raman Scattering of Ca-Substituted YBa2Cu3O7-d Synthesized by Polymerized Complex Method

Two types of Ca-substituted Y123 phase, (A) Y1-0.75xBa2-0.25xCaxCu3O7-d and (B) Y1-xCaxBa2Cu3O7-d have been prepared by a polymerized complex method X-ray powder diffraction and complex magnetic susceptibility measurements have shown that only type (A) is virtually of single phase without any impurities such as BaCuO2 and Y2BaCuO5. The superconducting transition temperature Tc decreases from 92.2K (x=0) to 83.2K (x=0.2) with increasing x in (A). Furthermore, we investigated the effect of Ca-substitution on phonon Raman spectra of type (A) by using a micro-Raman spectrometer. Ba and 0(4) phonons are significantly shifted towards lower frequencies by 3cm-1 and 4cm-1, respectively, when x is increased from 0 to 0.2. A possible origin of the decrease in both Tc and Ba-0(4) layers phonon energies are discussed in terms of both hole doping in the CuO2 planes and internal pressure induced by the Ca-substitution.