Temperature‐stable direct current‐biased energy storage in barium titanate‐based lead‐free ceramics via paraelectric engineering

Abstract High‐energy‐density multi‐layer ceramic capacitors are essential for high‐density power converters. Lead‐free barium titanate (BaTiO 3 )‐based ferroelectric ceramics are widely employed in low‐voltage scenarios, owing to their high permittivity. However, the ferroelectric state reveals strong dielectric nonlinearity, which limits applications for high‐density power converters working at high voltages. At the paraelectric state, the dielectric nonlinearity is significantly lower, which, however, only occurs at about 130°C or above. In this work, BaTiO 3 is modified with La(Zn 2/3 Nb 1/3 )O 3 to stabilize the paraelectric state within the operating temperature range through paraelectric engineering. The optimized 0.92BaTiO 3 ‐0.08La(Zn 2/3 Nb 1/3 )O 3 ‐1 wt.%SiO 2 ceramic exhibits excellent temperature stability, with a small energy density variation below 3% and high efficiency above 95% at a severe electric field of 200 kV/cm direct current (DC) superimposed with 50 kV/cm AC over a wide temperature range of 25–125°C. The high efficiency is related to the consistency between grain and grain boundary contributions from impedance analysis. The excellent temperature stability is elucidated by deconvolution of temperature‐dependent current density‐electric field curves, which specifies that the dominant linear contribution and minimal leakage current remain nearly unchanged against various temperatures at DC‐biased electric fields. Moreover, the optimized ceramic demonstrates remarkable frequency stability in the range of 5–200 Hz and outstanding cycling reliability up to 10 5 cycles, with the variation of discharged energy density less than 1% and 1.5%, respectively. The proposed paraelectric engineering paves a promising way for enhancing DC‐biased energy storage with temperature stability in lead‐free ferroelectrics towards high‐density power converters.