High energy-storage performance of lead-free Ba0.4Sr0.6TiO3–Sr0.7Bi0.2TiO3 relaxor-ferroelectric ceramics with ultrafine grain size

Abstract

Relaxor-ferroelectric (RFE) ceramics possess slender ferroelectric hysteresis loop and low remnant polarization ( P r ). They have great potential to provide excellent energy-storage performance as dielectric energy-storage materials. Herein, a lead-free 0.8Ba 0.4 Sr 0.6 TiO 3 –0.2Sr 0.7 Bi 0.2 TiO 3 (0.8BST–0.2SBT) RFE ceramic with high energy-storage performance has been realized successfully. The addition of Bi 3+ and increase in Sr 2+ content at the A site of the BST can effectively inhibit the growth of grains for high breakdown strength ( E b ). As a result, an ultrafine average grain size of 0.7 μm was obtained in 0.8BST–0.2SBT RFE ceramic, affording a high E b of 300 kV/cm. Further investigation revealed that the mutual conversion of short-range polar nanoregions and long-range-ordered ferroelectric domains upon application and withdrawal of a 300 kV/cm applied electric field resulted in a high maximum polarization ( P max ) of 31 μC/cm 2 and a low P r of 2.5 μC/cm 2 . Hence, the 0.8BST–0.2SBT RFE ceramic simultaneously exhibited a high recoverable energy-storage density of 3.3 J/cm 3 and a high energy-storage efficiency of 85% at 300 kV/cm. Additionally, a good energy-storage performance was reported over a temperature range of 50°C-120 °C and frequency from 10 to 1000 Hz, making the 0.8BST-0.2SBT RFE ceramic a potential lead-free dielectric energy-storage material.