Electrical properties of Sm-doped BiFeO$_3$ ceramics

The results of a study of the electrical properties of ceramics Bi$_{1-x}$Sm$_x$FeO$_3$ ($x$ = 0.05–0.20), synthesized by the technology of spark plasma sintering of nanopowder, are presented. X-ray diffraction (XRD) showed a change in the structure of bismuth ferrite from rhombohedral to orthorhombic with increasing samarium concentration. It has been found that the substitution of samarium improves the dielectric properties of $\varepsilon_r$ and $\tan\delta$, while the doped bismuth ferrite in the orthorhombic Pbam and Pnma phases has higher dielectric permittivity values than in the rhombohedral R3c phase. A decrease in leakage currents with increasing Sm concentration at temperatures up to 300$^\circ$C was found. Near the Neel temperature, all Bi$_{1-x}$Sm$_x$FeO$_3$ compositions demonstrate a decrease in the temperature growth rate $\sigma_{\mathrm{ac}}$. An analysis of the frequency dependence of the conductivity $\sigma_{\mathrm{ac}}(\omega)$ at different temperatures was carried out based on the universal power law of Johnsher $\sigma\sim\omega^s$.