Enhanced Energy Storage Properties in Lead-Free (Na 0.5 Bi 0.5 ) 0.7 Sr 0.3 TiO 3 -Based Relaxor Ferroelectric Ceramics through a Cooperative Optimization Strategy.

Although relaxor ferroelectrics have been widely investigated owing to their various advantages, there are still impediments to boosting their energy-storage density ( W rec ) and energy-storage efficiency ( η ). In this paper, we propose a cooperative optimization strategy for achieving comprehensive outstanding energy-storage performance in (Na 0.5 Bi 0.5 ) 0.7 Sr 0.3 TiO 3 (NBST)-based ceramics by triggering a nonergodic-to-ergodic transformation and optimizing the forming process. The first step of substituting NaNbO 3 (NN) for NBST generated an ergodic state and induced polar nanoregions under the guidance of a phase-field simulation. The second step was to apply a viscous polymer process (VPP) to the 0.85NBST-0.15NN ceramics, which reduced porosity and increased compactness, resulting in a significant polarization difference and high breakdown strength. Consequently, 0.85NBST-0.15NN-VPP ceramics optimized by this cooperative two-step strategy possessed improved energy-storage characteristics ( W rec = 7.6 J/cm 3 , η = 90%) under 410 kV/cm as well as reliable temperature adaptability within a range of 20-120 °C, outperforming most reported (Na 0.5 Bi 0.5 ) TiO 3 -based ceramics. The improved energy-storage performance validates the developed ceramics' practical applicability as well as the advantages of implementing a cooperative optimization technique to fabricate similar high-performance dielectric ceramics.