Dielectric properties and impedance spectroscopic study of (1−x)[0.90NaNbO₃–0.10Bi(Mg_0.5Ta_0.5)O₃]–x(Bi_0.5Na_0.5)_0.7(Sr_0.7La_0.2)_0.3Ti_0.9Zr_0.1O₃ ceramics

The solid-state reaction method was employed to synthesize (1−x)[0.90NaNbO₃–0.10Bi(Mg_0.5Ta_0.5)O₃]–x(Bi_0.5Na_0.5)_0.7(Sr_0.7La_0.2)_0.3Ti_0.9Zr_0.1O₃, denoted as (1−x)(NN–BMT)–xBNSLTZ (xBNSLTZ). XRD analysis of xBNSLTZ confirmed that all samples possessed a pure perovskite structure. SEM micrographs demonstrated homogeneous grain distribution and minimal porosity. With an increasing concentration of BNSLTZ, there was a gradual reduction in average grain size. Impedance spectroscopy was utilized to investigate the electrical properties of xBNSLTZ across a frequency sweep of 10 Hz–1 MHz and over a temperature range of 420–560 °C. The complex impedance and modulus spectra reveal non-Debye-type dielectric relaxation, indicative of two contributing mechanisms: grain and grain boundary effects on conduction. Electric modulus analysis indicated that the low-frequency relaxation process was temperature independent. The dc conductivity variation with temperature follows the Arrhenius equation. The ac conductivity was found to adhere to Jonscher power law. The E_a (the relaxation activation energy) and E_c (conductance activation energy) confirmed the relaxation mechanism of 0.3BNSLTZ is dipolar conduction. The dielectric properties showed a significant dependence on both frequency and temperature. A dielectric anomaly pointed to the presence of a single relaxation behavior. It was observed that an increase in BNSLTZ concentration led to a decrease in the maximum dielectric constant. Optimum performance was obtained with the 0.3BNSLTZ ceramics, which has the smallest average grain size (1.54 μm), considerable resistance value (R ~ 1000 K  \({\Omega }cm\) $\mathrm{\Omega }cm$ ), and moderate dielectric constant (ε_r ~ 600), superior to the pure NN-BMT ceramic. These results demonstrate that the electrical property of the xBNSLTZ ceramics have some potential value in the application of electrical materials.