(BiNa)TiO-NaNbO-Bi(MgZr)O Lead-Free Relaxor Antiferroelectric Ceramics Featuring Ultrahigh Temperature-Insensitive Energy-Storage Performance.

The development of lead-free dielectric ceramics with superior energy-storage performance is critical for next-generation pulsed-power capacitors. This work presents a breakthrough in lead-free (0.8-)(BiNa)TiO-0.2NaNbO-Bi(MgZr)O relaxor antiferroelectric ceramics featuring temperature-insensitive antipolar nanoregions with 4 symmetry, as confirmed by ex- and in situ XRD, Raman spectroscopy, and TEM analysis. In-situ piezoresponse force microscopy demonstrates the electric-field-driven reversible transformation between the antipolar nanoregions and ferroelectric microdomains, accompanied by rapid recovery kinetics upon field removal. This behavior enables a linear-like polarization-field response with minimal hysteresis. Moreover, the synergistically improved grain morphology and band structure contribute to a significantly enhanced breakdown strength. As a result, a superb recoverable energy density ≈ 8.6 J/cm and a high energy efficiency η ≈ 85.5% are simultaneously achieved under 55 kV/mm in the = 0.20 composition, which also exhibit a remarkable thermal stability ( = 4.2 ± 1.7% J/cm, η = 84.9 ± 4.0%, 20-260 °C) and ultrafast charge-discharge capabilities (Powder density = 264.7 MW/cm, discharge energy density = 5.1 J/cm, discharge time < 30 ns). These findings demonstrate a promising strategy for exploiting lead-free dielectrics with desirable overall energy-storage features for capacitor applications.