Tailoring ferroelectric polarization and relaxation of BNT-based lead-free relaxors for superior energy storage properties.

• A high W r of 4.97 J/cm3 and an η of 84.4% are obtained in BNT-based ceramics. • The W r of 2.73 J/cm3 with η of 80.6% are obtained at 140 ℃. • A superior temperature performance compared with other typical dielectric materials. • A strategy of precisely adjusting the relaxation and ferroelectricity states. Dielectric energy storage materials have attracted much attention because of their wide applications in the electronics industry. However, low energy storage density and poor thermostability limit their application. In this work, a strategy was proposed to prepare lead-free relaxor ferroelectric ceramics with ultra-high energy storage properties and superior temperature stability by precisely adjusting the relaxation and ferroelectricity states and increasing the electric field intensity. An ultra-high recoverable energy storage density (W r) of 4.97 J/cm3 and an efficiency (η) of 84.4% are simultaneously obtained for the 0.95(0.9Bi 0.5 Na 0.5 TiO 3 -0.1Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3)-0.05BaSnO 3 ceramic. Moreover, a high W r of 2.73 J/cm3 with brilliant η of 80.6% are obtained in the ceramic at 140 ℃ and there is almost no thermal degradation of energy storage properties from 25 ℃ to 140 ℃. The W r and η have decreased by 2.2% and 1.9% after 105 cycles under 200 kV/cm, respectively, which demonstrates the good cycle stability of the sample. A discharge power density of up to 99.0 MW/cm3 is obtained in the 0.95(0.9Bi 0.5 Na 0.5 TiO 3 -0.1Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3)-0.05BaSnO 3 ceramic and the good charge and discharge performance of this sample is important for practical applications. [ABSTRACT FROM AUTHOR]