Enhancement of recoverable energy density and efficiency of lead-free relaxor-ferroelectric BNT-based ceramics

Abstract Electrostatic capacitors with simultaneously excellent recoverable energy density (Wrec) and efficiency (η), and wide operate temperature range are currently the main challenge in applications of modern electronics and electrical power systems. Here, a series of lead-free relaxor-ferroelectrics 0.85[(1-x)Bi0.5Na0.5TiO3-xBi0.1Sr0.85TiO3]- 0.15KNbO3 ceramics with superb energy storage properties are prepared using solid-state reaction method. An excellent Wrec of 3.72 J/cm3 accompany with high η of 90.7% is attained concurrently with the composition of x= 0.3 under 290 kV/cm, which show remarkable advantages over recently reported lead-free ceramics. Meanwhile, superior thermal stability (20 ∼ 200 °C) and frequency stability (1 ∼ 1000 Hz) are also achieved. Moreover, by means of charge-discharge evaluations, the stored energy is released in an extremely short discharge time of 55 ns, regardless of variations in the temperature. All these characteristics demonstrate that this ceramic can be considered promising candidates for high power energy storage applications over broad temperature range.