Fulfilling X9R specification in CeO2 modified BNBST-based relaxor ferroelectric energy storage ceramic capacitors

Future low-voltage driven capacitor devices are appealed to employ the eco-friendly ceramics featured with high-stable dielectric energy storage capabilities. Herein, the dielectric energy storage properties of (Bi0.5Na0.5)0.65(Ba0.3Sr0.7)0.35(Ti0.98Ce0.02)O3+8 wt% K0.5Na0.5NbO3+x wt% CeO2 (BNBSTCK + Cx) lead-free relaxor ferroelectric ceramics were comprehensively investigated. By maintaining the relaxor ferroelectric phases near room temperature and disrupting the ferroelectric long-range order via CeO2 additive, the EIA X9R specification was fulfilled at the best composition of x = 8 over a wide range of −74∼208 °C with a relatively high dielectric constant εr = 904 and low loss tanδ = 10−3 (@25 °C & 1  kHz). Meanwhile, the good recoverable energy storage density Wrec = 0.77  J/cm3 and high efficiency η = 91.6% were achieved only at a low electric field of 95  kV/cm. Furthermore, these ceramics exhibited exceptional frequency and cycle dependent energy storage stability, which could guide the design ideas of long-life X9R ceramic capacitors suitable for high and low working temperature environments in low-voltage driven energy storage applications.