Achieving Ultrahigh Energy-Storage Density with Excellent Thermal Stability in Sr_0.7Bi_0.2TiO₃-Based Relaxors via...

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_0.7Bi_0.2TiO₃. Therefore, an ultrahigh W_rec ∼ 8 J/cm³ and a superior efficiency (η) ∼ 91% are accomplished in the 0.98[0.56(Sr_0.7Bi_0.2)TiO₃-0.44(Bi_0.5Na_0.5)TiO₃]-0.02 Bi(Mg_0.5Ti_0.5)O₃ sample. The achieved W_rec value is record high in Sr_0.7Bi_0.2TiO₃-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 (ΔW_rec < 12.7% and Δη < 10.4%, -50-200 °C), frequency (ΔW_rec < 2.69% and Δη < 2.06%, 0.5-500 Hz), and fatigue-resistant stability (ΔW_rec < 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.