Energy storage properties and stability in Nd3+/Ta5+ modified 0.6Na0.5Bi0.5TiO3-0.4Sr0.7Bi0.2TiO3 lead-free relaxor ferroelectric ceramics under a low electric field

Abstract

Due to the prevalence of wearable electronic devices, Lead-free dielectric ceramics with excellent recoverable energy storage density and efficiency at low electric fields are well worth investigating. Moreover, maintaining excellent energy storage performance (ESP) in different environments is a huge challenge for researchers. In this study, 0.6Na0·5Bi0·5TiO3-0.4Sr0·7Bi0·2TiO3 lead-free relaxor ferroelectric ceramics were modified by (Sr0.7Nd0.2) (Ta0·4Ti0.5)O3 (BNST-xSNTT x = 0, 0.02, 0.04, 0.06). On one hand, BNT has a very high polarization strength, making it a very suitable basic element for designing high energy storage dielectric materials. On the other hand, Sr0·7Bi0·2TiO3 and (Sr0.7Nd0.2) (Ta0·4Ti0.5)O3 were introduced to improve the performance of ceramics, such as inducing polar nanoregions (PNRs), refining grain size, and increasing impedance. The results demonstrate that the energy storage characteristics of BNST-xSNTT were enhanced by introducing SNTT to the BNST. The ceramics exhibited a significant grain size reduction from 0.946 μm (x = 0) to 0.346 μm (x = 0.06). In addition, a great polarization difference (ΔP = 44.29 μC/cm2) was simultaneously achieved in the x = 0.02 sample. As a result, BNST-2SNTT (x = 0.02) ceramic obtained an excellent recoverable energy density of 3.24 J/cm3 and a satisfactory efficiency of 81.4 % at a low electric field of 190 kV/cm. Furthermore, the BNST-2SNTT ceramic exhibits excellent temperature stability (20°C–140 °C), frequency stability (1 Hz–500 Hz), and cycling reliability (10°-106 cycles). The corresponding fluctuation of ESP is less than 5 %. These properties indicate that the BNST-2SNTT ceramic is an excellent dielectric material for energy storage.