Remarkable energy storage performances of tungsten bronze Sr0.53Ba0.47Nb2O6-based lead-free relaxor ferroelectric for high-temperature capacitors application

Abstract

Simultaneously integrating outstanding energy storage performance and good temperature stability in advanced ferroelectrics is a promising strategy to boost the practical application for next-generation high-temperature pulse devices. However, these constrains cannot happen hand-in-hand, and the realization of high-performance dielectric capacitors always comes at the expense of high-temperature tolerance due to thermal breakdown, leading to that the trade-off relationship as above mentioned was not substantially relieved in perovskite relaxor materials. Guided by structural manipulation of ferroelectricity/relaxation, we propose an alternative material system Sr(0.53–0.15x)Ba0.47Gd0.1xNb2-xTaxO6 with a tetragonal tungsten-bronze structure (TTB) to remedy the longstanding problem for balancing energy storage−temperature steadiness. In this work, a lead-free Gd/Ta-co-doped Sr0.53Ba0.47Nb2O6-based (SBN) ferroelectric ceramics were prepared, which shows a satisfied recoverable energy storage density (Wrec ∼6.23 J cm−3) at 470 kV/cm at room temperature and Wrec remained above 5 J cm−3, coupling well with the efficiency η above 85% over a wide range of temperatures from 20 to 140 °C. Accompanying with the structural modulation from commensurate to incommensurate side induced by Gd-Ta-co-dopant, the relaxor characteristics were regulated effectively compared to pristine SBN ceramics, which resulted in the large distortion of BO6 polar unit and enhanced polarization as corroborated from the Raman patterns. Meanwhile, Gd and Ta co-doping also endowed the remarkable improvement of breakdown strength owing to the effectively suppressed conductivity and leakage current density by the increased intrinsic bandgap. The novel and effective strategy proposed in this study is of great instructive significance for further designing dielectric ceramics with superior energy storage performance and good temperature stability as well as for the further development of Multi-Layered Ceramic Capacitors (MLCC) and other advanced ceramic capacitors.