Lead-free (0.93 − x)Bi0.5Na0.5TiO3–0.07BaTiO3–xNaNbO3 relaxor ferroelectrics for energy storage applications

In this work, (0.93 − x)Bi_0.5Na_0.5TiO₃–0.07BaTiO₃–xNaNbO₃ (BNT–0.07BT–xNN) lead-free energy storage ceramics were designed on the basis of the phase diagram of this system. The phase structure and energy storage property were studied. The NN substitution into BNT–BT increased the crystal structure symmetry and induced an obvious disruption of the ferroelectric order. At x = 0.20, an extremely slim P–E hysteresis loop along with a large recoverable energy storage density (W_rec) of 2.08 J/cm³ and a high energy storage effificiency (η) of 81% was obtained at a moderate electric field of 160 kV/cm. The BNT–BT–0.02NN ceramic possessed a high discharge energy density (W_d ~ 1.44 J/cm³) and a fast discharge speed (t_0.9 ~ 153 ns) at an electric field of 160 kV/cm. These results show that the BNT–0.07BT–xNN material may be a promising candidate for capacitors.