Phase structure, AC conductivity, and thermistor performance in 0.70Na₀.₅Bi₀.₅TiO₃–0.30BaMn₀.₅Ti₀.₅O₃ ceramics

Abstract

This study investigates the structural, dielectric, and magnetic properties of a 0.70Na₀.₅Bi₀.₅TiO₃ − 0.30BaMn₀.₅Ti₀.₅O₃ composite synthesized via the solid-state reaction method. X-ray diffraction (XRD) analysis confirms a tetragonal P4-mm crystal structure, with Rietveld refinement providing a good fit. A minor TiO₂ rutile phase is detected. Scanning electron microscopy (SEM) reveals agglomerated, irregular nanoparticles, which influence the dielectric behavior of the material. Dielectric studies show that the permittivity decreases with increasing frequency, in agreement with dipole relaxation behavior described by the Havriliak-Negami model. AC conductivity measurements, following Jonscher’s power law, suggest thermally activated conduction mechanisms. Impedance spectroscopy, represented by a Nyquist plot, exhibits a single semicircle, indicative of bulk properties, with impedance decreasing at higher temperatures. Lattice expansion, inferred from the shift of the (110) XRD peak to lower 2θ angles, suggests Ba²⁺ ion substitution. The Williamson-Hall method estimates the crystallite size and strain, and the calculated tolerance factor (t = 1.25) indicates tetragonal distortion. These results demonstrate that the 0.70Na₀.₅Bi₀.₅TiO₃ − 0.30BaMn₀.₅Ti₀.₅O₃ composite possesses favorable structural, dielectric, and magnetic characteristics, positioning it as a potential candidate for electronic applications.