Lead-free relaxor-ferroelectric ceramics for high-energy-storage applications

Abstract

Relaxor-ferroelectric ceramics capacitors have been in the front lines of investigations aimed at optimizing energy density due to their high P_max, suppressed P_r, and high BDS levels, attributed to their highly dynamic polar nano-regions. A set of (1 − x)SrTiO₃–x[0.88BaTiO₃–0.12Bi(Li_0.5Ta_0.5)O₃] ceramics (x = 0, 20, 40, 60 and 80 mol%), abbreviated as (1 − x)ST–x(BT–BLT), was designed and fabricated via a solid-state reaction route. A striking energy-storage density of 2.24 J cm⁻³, coupled with a high efficiency of η = 81% at 300 kV cm⁻¹, was measured for these (1 − x)ST–x(BT–BLT) ceramics. The incorporation of BT–BLT ceramics was found to dramatically transform the paraelectric state of strontium titanate into the relaxor-ferroelectric state, by introducing broad relaxor behavior. The energy storage properties of the ceramic with x = 60 mol% showed outstanding stability in frequency (10–100 Hz) and temperature (20–120 °C), with minimal variation of (±≤0.5%), over the course of 10⁵ cycles. Moreover, under various electric fields, rapid charge and discharge (≤1.5 μs) was also observed for this x = 60 mol% ceramic. Most significantly, the outcomes of this study are expected to provide a standard for other emerging lead-free dielectric ceramics displaying very good energy-storage properties and excellent electric field endurance, which are of pragmatic importance for cutting-edge pulsed power technology.