Large energy density and high efficiency achieved simultaneously in Bi(Mg0.5Hf0.5)O3-modified NaNbO3 ceramics

A novel lead-free relaxor ferroelectric ceramics, (1-x)NaNbO3-xBi(Mg0.5Hf0.5)O3 [NN-xBMH, x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.25] were designed and fabricated for the first time via the standard solid-phase reaction method. The dielectric, ferroelectric, and impedance properties of the NN-xBMH ceramics were tested. Normal ferroelectrics were induced into relaxor ferroelectrics with the introduction of BMH, and the hysteresis loops became slender; This is beneficial to improve the energy storage density and efficiency of ceramic capacitors. Superior breakdown strength (370 kV/cm) is achieved in NN-0.20BMH ceramic with the recoverable energy storage density (Wrec = 3.51 J/cm3) and efficiency (η = 93.77 %). In addition, excellent frequency (1–1000 Hz) and temperature (30–120 °C) stability shows that ceramics have the actual potential in the application of ceramic capacitor. Excellent charge and discharge performances with a high power density (PD = 118 MW/cm3) and current density (CD = 990 A/cm2) along with an ultra-fast discharge rate (50 ns) were gained.