Achieving Ultrahigh Energy-Storage Density with Excellent Thermal Stability in Sr0.7Bi0.2TiO3-Based Relaxors via Polarization Behavior Modulation

Dielectric capacitors possessing the inherent superiorities of high power density and ultrafast charge–discharge speed make their utilization in energy-storage devices extremely propitious, although the relatively low recoverable energy-storage density (Wrec) may impede their applications. In this work, unlike the mainstream approach of destroying long-range ferroelectric/antiferroelectric order and inducing relaxor properties to achieve a high Wrec value, we have selected end members with a high polarization gene to promote the polarization behavior of the typical relaxor Sr0.7Bi0.2TiO3. Therefore, an ultrahigh Wrec ∼ 8 J/cm3 and a superior efficiency (η) ∼ 91% are accomplished in the 0.98[0.56(Sr0.7Bi0.2)TiO3-0.44(Bi0.5Na0.5)TiO3]-0.02 Bi(Mg0.5Ti0.5)O3 sample. The achieved Wrec value is record high in Sr0.7Bi0.2TiO3-based systems as far as we know. The polarization-enhancement behavior can be explained by the phase field simulation results, phase content variance in X-ray diffraction Rietveld refinement, hardening trend in Raman spectroscopy, domain morphology, and local symmetry in transmission electron microscope analysis. Meanwhile, the ceramic possesses excellent thermal stability (ΔWrec < 12.7% and Δη < 10.4%, −50–200 °C), frequency (ΔWrec < 2.69% and Δη < 2.06%, 0.5–500 Hz), and fatigue-resistant stability (ΔWrec < 0.08% and Δη < 0.2%, up to 1 × 105 cycles). Accordingly, this work proposes a design idea to tailor the polarization behavior and energy-storage properties of typical relaxors.