Phase-Transition Induced Optimization of Energy Storage and Temperature Stability of NaNbO3 Doped BNBST Ceramics

The 0.5Bi 0.5 Na 0.5 TiO 3 −0.5Ba 0.3 Sr 0.7 TiO 3 (BNBST) ceramic is a relatively good relaxation component with tripartite phase and tetragonal phase coexisting at room temperature. Tripartite R3c is a polar phase, which can transform to long range ordered ferroelectric structures under the action of an applied electric field, exhibiting large remnant polarization ( P r ), which limits its application in energy storage. In this work, we designed NaNbO3 (NN) modified Bi 0.5 Na 0.5 TiO3-Ba 0.3 Sr 0.7 TiO 3 ceramics to prepare (1− x ) (0.5Bi 0.5 Na 0.5 TiO 3 −0.5Ba 0.3 Sr 0.7 TiO 3 )− x NaNbO 3 (abbreviated as (1− x )BNBST- X nn, x = 0, 0.05, 0.10, 0.15, 0.20, 0.25) relaxor ferroelectrics. By increasing the NN amount, the phase composition is regulated to induce the transformation of the polar phase R3c to the weakly polar phase P4bm , leading to a smaller P r . The ferroelectric test results show that the ceramic sample with x = 0.1 achieves a high effective energy storage density ( W rec = 2.58 J cm −3 ) and energy storage efficiency ( ƞ = 91%) at 140 kV cm −1 .