Enhanced energy storage properties of KNbO3 modified (Bi0.5Na0.5)TiO3–BaTiO3 based lead-free relaxor ferroelectric ceramics

Dielectric capacitors are widely used in pulse devices because of their fast charge/discharge speed. However, the low energy storage density limits their application. In this work, (1 − x)(Bi0.5Na0.5)0.94Ba0.06Ti0.99(Y0.5Nb0.5)0.01O3-xKNbO3 (BNBTYN-100xKN) lead-free relaxor ferroelectric ceramics were fabricated via a solid-state sintering technique. K+ and Nb5+ were completely diffused into the BNBTYN lattice and formed solid solutions. The incorporation of KNbO3 reduced the symmetry of BNBTYN-100xKN ceramics and destroyed the long-range ordered ferroelectric domains, leading to thinning of hysteresis loops. The relaxor degree increased with the KN content, resulting in the improvement of efficiency. Therefore, using BNBTYN-5KN ceramics an energy storage density of 1.246 J cm−3 and an efficiency of 78.7% at 104 kV cm−1 were obtained. In addition, the BNBTYN-5KN ceramics exhibited this energy storage density with outstanding temperature stability (in the range of 20–120 °C) and excellent fatigue resistance. These results reveal that BNBTYN-5KN ceramics is a promising material for energy storage.