Enhanced energy storage and temperature-stable dielectric properties in (1-x)[(Na0.4K0.1Bi0.5)0.94Ba0.06TiO3]-xLa0.2Sr0.7TiO3 lead-free relaxor ceramics

Abstract

With the continuous growth in sustainable and renewable technologies, ceramic capacitors are emerging as a promising energy storage device. Lead-free (1-x)[(Na0.4K0.1Bi0.5)(0.94)Ba0.06TiO3]-xLa(0.2)Sr(0.7)TiO(3) (0 <= x <= 0.40) ceramics were prepared using the solid-state reaction technique for obtaining relaxor characteristics with improved energy storage density, efficiency, and temperature stability of dielectric permittivity. A high recoverable energy density (W-r) similar to 2.39 J/cm(3) with a good efficiency (eta) of similar to 75.21% was obtained for x = 0.30 composition under 220 kV/cm applied field. The specimen x = 0.30 exhibited excellent fatigue resistance during 10(5) cycles and good temperature stability of energy storage characteristics (W-r > 0.87 J/cm(3), eta > 74%) in the temperature range of 25-180 degrees C under 100 kV/cm. In addition, the temperature range in which the dielectric permittivity variation was less than +/- 15% was very wide (204 degrees C (63-267 degrees C) and 275 degrees C (39-314 degrees C) for x = 0.30 and 0.20 specimens, respectively). Significant improvements in material performance were attributed to A-site engineering, which resulted in a mixture of P4bm and R3c polar nano regions (PNRs), leading to reduced hysteresis loss and temperature-stable dielectric permittivity. Additionally, the size of PNRs ranged between 3 and 6 nm, with the P4bm phase dominating in the x = 0.30 specimen, leading to a large maximum polarization under an applied electric field. Therefore, (1-x)[(Na0.4K0.1Bi0.5)(0.94)Ba0.06TiO3]-xLa(0.2)Sr(0.7)TiO(3) relaxor ceramics are promising for high energy density materials and electronic applications requiring high permittivity stability over a wide temperature range.