Solid-state synthesis of Pb2Sr2CaCU3-ySx and conducting properties

Abstract

In this study complete substitution of O by S in Pb-Sr-Ca-Cu-O superconducting system that has the general formula Pb2Sr2MCu3O8+delta (M = Y, Ca) had been attempted. For this purpose, solid-gas reactions of solid mixture, PbO, Sr(NO3)(2), CaO and CuO with a sulfidizing gas consisted of COS, CS2, CO, CO2 and sulfur vapour were performed. For M, only Ca was used. The obtained product Pb2Sr2CaCu3-ySx, was characterized by XRD, IR, SEM, EDX, conductivity measurements and chemical analysis. X-Ray powder diffraction pattern of Pb2Sr2CaCu3-ySx was found to be very similar to PbS diffraction pattern reported in JCPDS Card No.5-592 which has a rock salt structure with a = 5.946 Angstrom. Pb2Sr2CaCu3-ySx. was indexed in monoclinic system with the refined unit cell parameters of a = 5.947(8), b = 5.941(3), c = 11.98(1) Angstrom and beta = 90.19(9)degrees. Since V unit cell dimension is almost twice of a and b, it is concluded that a superstructure formation had resulted which is common for complex sulfides. The absence of metal oxygen bands in IR and O bands in EDX spectra is taken to be the proof of the complete substitution of O by S by solid gas reactions. The conductivity of Pb2Sr2CaCu3-ySx, was measured by four-probe conductivity technique and was found to be metallic.