(1-x)(Na₀.₅Bi₀.₅)TiO₃-xCaTiO₃ ceramics: Investigating structural and microstructural features for enhanced dielectric properties

Abstract

(1-<i>x</i>)(Na₀.₅Bi₀.₅)TiO₃-<i>x</i>CaTiO₃ Lead-free piezoelectric systems, positioned near the morphotropic phase boundary, were synthesized for varying compositions (x = 0.0, 0.05, 0.10, 0.15, and 0.20) using the solid-state reaction route. This study delves into the comprehensive investigation of the compositional effects on phase, structure, and electrical characteristics. Specifically, a morphotropic phase boundary (MPB) involving rhombohedral (<i>R</i>3<i>c</i>) and orthorhombic (<i>Pnma</i>) structures was seen in a (1-<i>x</i>)NBT-<i>x</i>CT crystal structure close to the composition of x = 0.10. Information on the pure phase formation and grain size of the intended composite system has been obtained using Rietveld refinement of the X-ray diffraction (XRD) diagram as well as scanning electron microscopy (SEM). The impact of the CT phase on the NBT lattice was investigated through an analysis of the charge density distribution. Using Williamson-Hall plots from XRD data, the average particle diameter was estimated to be between 131.87 nm and 136.54 nm. The relative permittivity increases with the addition of Ca²⁺, according to dielectric measurements. All ceramics exhibit a diffuse phase transition near (Tm) with a diffusivity range of 1.5-1.8, and a downward shift in depolarization temperature (Td). At the morphotropic phase boundary (MPB), excellent dielectric properties were observed at x = 0.10, which are attributed to the presence of both rhombohedral and orthorhombic structures as well as an appropriate particle size. The conduction process at different temperatures is thermally activated, as determined by the frequency-dependent ac conductivity.