Thermal expansion and Vickers hardness measurements on Bi1.6Pb0.4Sr2Ca2−xSmxCu3Oy superconductors

In this work, Bi1.6Pb0.4Sr2Ca2−xSmxCu3Oy (x = 0.0000, 0.0005, 0.0010, 0.0050, 0.0100, 0.1000, 0.5000, 1.0000, 1.5000) superconductors were prepared by conventional solid-state reaction method. The effect of the substitution of Sm for Ca in the high-Tc phase Bi-2223 was investigated by DTA, thermal expansion coefficient, Vickers microhardness, XRD and SEM analysis. The lattice constants and volume fractions are estimated from XRD analysis. The thermal expansion coefficient, the microhardness, the volume fraction, and the lattice constants strongly depend on the Sm content of the samples. XRD data show that the high-Tc phase decreases and the low-Tc phase increase as the Sm substitution changes from x = 0.0–1.5. The coefficients of thermal expansion (in the range of 30–800 °C) of the pure (x = 0.0) and high doped (x = 1.5) samples were 7.90 × 10−7 and 5.70 × 10−7 °C−1, respectively. The results of Vickers hardness measurements varied between 0.254 and 0.623 GPa as increasing the Sm concentration.