Investigation of electrocaloric effect and scaling behavior with correlation of structural, electrical, and impedance properties in Sn-substituted NBT–BT ceramics near MPB

Abstract

The Sn-substituted 0.94 (Na_0.5Bi_0.5TiO₃) – 0.06 (BaTi_1-xSn_xO₃) (x = 0.11, 0.12, and 0.13 mol%) ceramics were synthesized using the conventional solid-state reaction method near the MPB. Rietveld refinement confirmed a single-phase perovskite structure, exhibiting a coexistence of monoclinic (Cc) and tetragonal (P4mm) crystal symmetries. Microstructural analysis through SEM revealed detailed grain distribution and surface morphology, while XPS provided comprehensive insights into elemental compositions, oxidation states, and average binding energies. The introduction of Sn led to a subtle increase in UV absorbance, accompanied by a marginal band gap enhancement. Temperature-dependent dielectric investigations revealed a pronounced impact of Sn substitution on ferro – to antiferro and antiferro – to – paraelectric phase transitions. The frequency dependence of AC conductivity at various temperatures was analyzed using Jonscher's power law. Complex impedance spectra (Cole-Cole plots) were fitted using different bricklayer models to investigate the contributions of grain, grain boundary, and interfacial resistances over a wide temperature range, showing a reduction in the semi-circular arc size and overall resistance due to grain boundary conduction. The electric field- and frequency-dependent P-E loop scaling properties were studied to analyze domain switching and polarization responses. Additionally, temperature-dependent ferroelectric studies were conducted to examine polarization behavior with thermal attenuation and to explore energy storage and electrocaloric properties.