Thermomechanical Analysis of (Cu0.5Tl0.5)-1223 Substituted by Pr and La

Abstract

The thermomechanical analysis (TMA) of Cu0.5Tl0.5Ba2a2−xRxCu3O10−δ, where R=Pr and La, with 0.0≤x≤0.15, was carried out in temperature range from 450 to 1145 K. The samples were prepared by single-step solid state reaction technique. The prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The superconductivity of the prepared samples was investigated by electrical resistivity measurement. The results showed that low substitution content enhanced the (Cu0.5Tl0.5)-1223 phase formation, while the higher substitution content degraded this phase. The higher superconducting transition temperatures Tc were found to be 114 K and 109 K at x= 0.025 for Pr- and La-substitutions, respectively The average linear thermal expansion coefficient increased as x increased, while the shrinkage temperature decreased as x increased. Those results were emphasized by porosity and Vickers microhardness calculations. Debye temperature θD was calculated from the linear thermal expansion coefficient data and correlated to Tc to estimate the electron-phonon coupling λep.