Achieving Ultrahigh Energy-Storage Density with Excellent Thermal Stability in Sr 0.7 Bi 0.2 TiO 3 -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 ( W rec ) 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 W rec value, we have selected end members with a high polarization gene to promote the polarization behavior of the typical relaxor Sr 0.7 Bi 0.2 TiO 3 . Therefore, an ultrahigh W rec ∼ 8 J/cm 3 and a superior efficiency (η) ∼ 91% are accomplished in the 0.98[0.56(Sr 0.7 Bi 0.2 )TiO 3 -0.44(Bi 0.5 Na 0.5 )TiO 3 ]-0.02 Bi(Mg 0.5 Ti 0.5 )O 3 sample. The achieved W rec value is record high in Sr 0.7 Bi 0.2 TiO 3 -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 (Δ W rec < 12.7% and Δη < 10.4%, -50-200 °C), frequency (Δ W rec < 2.69% and Δη < 2.06%, 0.5-500 Hz), and fatigue-resistant stability (Δ W rec < 0.08% and Δη < 0.2%, up to 1 × 10 5 cycles). Accordingly, this work proposes a design idea to tailor the polarization behavior and energy-storage properties of typical relaxors.