Superior thermal and frequency stability and decent fatigue endurance of high energy storage properties in NaNbO3-based lead-free ceramics

Abstract

Designing a well-performing and practical dielectric capacitor is a valuable but challenging theme in contemporary electrical devices. Dielectric capacitors rely on a high energy density and outstanding energy efficiency, which are difficult to achieve synchronously. To our satisfaction, ultrahigh recoverable energy density (Wrec) of 3.14 J/cm3 and extremely high energy efficiency (η) of 84.5% were observed synchronously in (1-x)NaNbO3-xBi(Zn0.5Zr0.5)O3 (xBZZ) (x = 0.12) lead-free bulk ceramic, which evidently outperforms most other lead-free materials. Interestingly, the introduction of Bi2O3 and ZrO2 exceedingly enhances the breakdown strength (Eb) and insulation of NaNbO3, which may be due to the decrease in sodium volatilization and oxygen vacancy formation, as well as cation disorder enhancement. The fine and dense grain size distribution is conducive to obtaining relatively large ΔP and small remnant polarization (Pr). More importantly, the comprehensive performance of the 0.12BZZ sample exhibits superior frequency stability (variation of Wrec < 2% against 1–100 Hz), optimum thermal stability (variation of Wrec < 2% over 20–160 °C) and decent fatigue endurance (variation of Wrec < 1% after 104 cycles). Moreover, of particular significance is that this new strategy supplies a feasible avenue to achieve impressive properties in unleaded ceramics for use as energy storage devices.