Effect of Sn Substitution on Structural Properties of Bi 2-xSn xSr 2CaCu 2O 8+δ Ceramics Superconductors

The effects of substitution of Bi by Sn in Bi_2-xSn_xSr₂CaCu₂O_8+δ with (x = 0-0.05) on the structural and physical properties were investigated in this paper. The samples were obtained by a solid-state reaction method and pressed uniaxially under 225 MPa before the last heat treatment. The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), and electron dispersive X-ray (EDX). XRD studies indicated that all prepared samples were single phase with a small fraction of Bi₂Sr₂CuO_6+δ secondary phase. The lattice parameters of the Bi-2212 and Bi(Sn)-2212 phases were identified using DicVol04 software by [Boultif et al.] The elemental compositions analysis, which was determined from EDX, indicated that the Sn introduced into the microstructure of Bi-2212 phase. The SEM micrographs show that the undoped sample consists of grains well connected with a random distribution. A very different microstructure is obtained for the doped samples, where the grains are more connected with a flat shape characteristic of the Bi-based superconductors. DC magnetic measurements show that the onset transition temperature, of about 81 K for the undoped sample, increases until about 86.2 K for the doped sample.