Modified energy storage properties of lead-free Sr0.3Bi0.35Na0.335Li0.015TiO3 ceramics with La3+ substitution via the solid-state combustion technique

Abstract

In this study, the influence of La3+ substitution on the phase structure, microstructure, electrical and energy storage properties of (Sr0.3Bi0.35Na0.335Li0.015)1-xLaxTiO3 (SBNLT-xLa) ceramics with x = 0–0.05, using the solid-state combustion technique, was investigated. X-ray diffraction (XRD) patterns indicated a pure perovskite structure formed, along with coexisting rhombohedral and tetragonal phases in all ceramics. The Rietveld refinement analysis showed the tetragonal phase increased while the rhombohedral phase decreased with increased La3+ content. The morphology of the SBNLT-xLa ceramics displayed polygonal grain shapes and anisotropic grain growth. Average grain sizes increased from 2.01 to 2.43 μm as x increased from 0 to 0.01 and afterwards decreased as x increased further. Both the measured density and maximum dielectric constant (ɛm) decreased from 5.48 to 5.29 g/cm3 and from 4667 to 2313, respectively, when x increased from 0 to 0.05. A decrease in the dielectric properties caused by the phase ratio shifting away from a morphotropic phase boundary (MPB) condition, poor microstructure and low density was produced with La3+ replacement. The maximum polarization (Pmax), remnant polarization (Pr) and coercive field (Ec) decreased with increased La3+ content. A decline in Pr and Ec improved the energy storage efficiency (ƞ) and energy storage loss (Wloss), resulting in enhanced energy storage properties. At x = 0.02, the ceramic showed good energy storage properties (Wtotal of 0.781 J/cm3, Wrec of 0.624 J/cm3, Wloss of 0.157 J/cm3 and ƞ of 79.8%), measured at 60 kV/cm.