Remarkably enhanced recoverable energy density in lead-free relaxor Ba_0.94Ca_0.06Ti_1−xSn_xO₃ ceramics by the synergistic effect of nano-domains and refined grains

High-performance dielectric ceramic capacitors is a promising candidate in energy storage devices. In this work, the energy storage performance of Ba_0.94Ca_0.06Ti_1−xSn_xO₃ (x = 0.04, 0.08, 0.12, 0.16) ceramics was systematically studied. Through modifying Sn⁴⁺ doping content, the breakdown strength of the ceramics is enhanced by 112.3% from 133.4 kV/cm (Ba_0.94Ca_0.06Ti_0.96Sn_0.04O₃) to 283.2 kV/cm (Ba_0.94Ca_0.06Ti_0.84Sn_0.16O₃). Accordingly, the recoverable energy density is greatly increased by 276.2%, that is, from 0.42 J/cm³ grow to 1.58 J/cm³. The enhanced energy storage properties could be ascribed to the following aspects: (1) the doping of Sn⁴⁺ with a larger ionic radius inhibits the migration of grain boundaries and therefore refines grains, resulting in a higher activation energy and a larger E_b; (2) the long range polar order is broke and polar nano-regions are formed, giving rise to lower energy barrier and smaller P_r; (3) the weakened ferroelectricity and delayed polarization saturation lead to higher W_rec owing to the fact that Sn⁴⁺ with d¹⁰ electronic configurations substitutes Ti⁴⁺ with d⁰. Our work provides a novel approach for enhancing energy storage performance in dielectric ceramic capacitors.