Temperature impedance spectroscopy of $(1-x)$Na$_{1/2}$Bi$_{1/2}$TiO$_3$–$x$LaMg$_{1/2}$Ti$_{1/2}$O$_3$ solid solutions

The dielectric properties of $(1-x)$Na$_{1/2}$Bi$_{1/2}$TiO$_3$–$x$LaMg$_{1/2}$Ti$_{1/2}$O$_3$ solid solutions (0 $\le x\le$ 0.4) were studied over the temperature range 650–1030 K by measuring the impedance spectra over the frequency range 25–10$^6$ Hz. The Curie temperature $T_C$ was determined as a function of the composition of the solid solutions. It is shown that $T_C$ decreases linearly with increasing $x$. The temperature dependences of the dc component $(\sigma_{dc})$ and the polarization component ($(\sigma'_{ac})$) of the real part of the conductivity are found. The activation energy for the conductivity $\sigma_{dc}$ is shown to increase abruptly as the temperature increases above approximately 770 K for all solid solution compositions. Over the temperature range corresponding approximately to the region of existence of the tetragonal phase of Na$_{1/2}$Bi$_{1/2}$TiO$_3$, the polarization component $\sigma'_{ac}$ of the solid solutions, as well as that of the pure compound, is anomalously high at low frequencies, which can be due to structural inhomogeneities.