Effects of Zn doping on crystal structure, Raman spectra and superconductivity of SmBa2Cu3O7−δ systems

Polycrystalline SmBa2Cu3−xZnxO7−δ (SBCZO) (x = 0.0–0.4) samples are prepared by the usual solid-state reaction technique. The effects of Zn doping on the structure, the grain morphology, Raman spectra and electronic transport properties of SBCZO systems have been investigated. The orthorhombic structure of the samples does not change remarkably. The samples become denser and grain boundary becomes unclear with the increase of Zn content. Raman spectra exhibit different features with increasing Zn content which shows that Zn ions act as strong scattering centers to the charge carriers in the CuO2 planes, enhance the disorder of the CuO2 planes and increase oxygen depletion in CuO chains. The measurements of the resistivity show that the superconducting transition temperature Tc decreases rapidly and the superconducting transition width increases gradually with increasing Zn contents. Furthermore, the changes of the samples’ normal state resistivity from metallic to semi-conducting behavior show the increase of heterogeneities with increasing Zn content which causes inter-grain or intra-grain disorders. All the results suggest that lattice disorder in the CuO2 planes, the oxygen content change in CuO chains and local weak superconductivity regions due to the substitution of Zn for Cu are related to the suppression of Tc in the SBCZO systems.