The effect of \textit{Sm} substitution on properties of Bi$_{1.6}$Pb$_{0.4}$Sr$_{2}$Ca$_{2-x}$Sm$_{x}$Cu$_{3}$O$_{y}$ superconductors.

The effect of the partial substitution of \textit{Ca} by \textit{Sm} in the \textit{Bi-2223} superconducting samples have been investigated in terms of XRD, magnetoresistivity, critical temperature, transport critical current density, and ac susceptibility. The samples were prepared by the conventional solid-state reaction method. XRD patterns are used to calculate lattice parameters and obtain about Bi-2223 phase ratio. The volume fraction was determined from the intensities of Bi-2223 and Bi-2212 peaks. The room temperature XRD patterns of the samples showed the presence of Bi-2223 phase decreases with increasing the \textit{Sm} content. We estimated the transition temperature, the activation energy values of the samples from the resistivity vs. temperature measurements in dc magnetic fields up to 0.6 T. We observed that transition temperature, $T_{c}$, and transport critical current density, $J_{c}$\textit{trans}, depend on the Sm substitution. They both decrease with increasing the \textit{Sm} substitution. Activation energy, $U_{0},$ is calculated from resistivity versus temperature at various magnetic fields in both high temperature region and low temperature region. It is observed that $U_{0}$ depend on both the \textit{Sm} content of samples and the applied magnetic field.