Single crystals with known Tc values of Y1-xPrxBa2Cu3O7-δ (YPr1:2:3) and YBa2Cu3-xZn3-xZnxO7-δ (YZn1:2:3) systems are studied by Raman measurements. The Raman spectra for (YPr1:2:3) single crystals show that the frequencies of Ba and Oz modes increase as the Pr content increases. The results are consistent with the hole-localization scheme proposed for the suppression of superconductivity in the polycrystalline YPr1:2:3 systems. On the other hand, in the YZn1:2:3 system, all the Raman modes do not change in frequencies. However, the FWHM of the Cu(2) mode increases with the decrease of Tc, indicating strong scattering of charge carriers by the substituted Zn ions in the CuO2 planes. The induced disorder in the CuO2 planes may be related with suppression of Tc in the YZn1:2:3 system. Thus, the suppression mechanism in the YZn1:2:3 systems seems to be different from that in the YPr1:2:3 systems.
Bibliographical noteFunding Information:
The authors are grateful for support from the Korea Science & Engineering Foundation under contract Nos. 931-0200-032-2 (ISY) and 941-0200-005-2 (WCL).