I. M. TangMahidol University2018-09-072018-09-071999-01-01International Journal of Modern Physics B. Vol.13, No.17 (1999), 2291-2298021797922-s2.0-0343989594https://repository.li.mahidol.ac.th/handle/123456789/25785The depressions of the Tc's of the "123" REBa2Cu3O7HTSC's due to the substitution of Zn2+ions into the Cu(2) layer are studied. The orthorhombic distortion which occurs in the "123" ceramics is assumed to induce a modification to the spin-fluctuation (SF) mediated pairing interaction which inturn causes the order parameters of these HTSC's to be of mixed (d + s)-wave symmetry. It is shown that part of the rapid depression of the Tc's caused by Zn2+substitution into the CuO2is due to a reduction of the SF-mediated pairing interaction. The differences in the rates of suppression of Tcdue to Zn2+doping in the different "RE-123" HTSC's are shown to be due to the changes in the orthorhombicity which depend on the size of the rare earth ions. © World Scientific Publishing Company.Mahidol UniversityPhysics and AstronomyArticleSCOPUS10.1142/S021797929900240X