Longwen Wu

Core-satellite BaTiO3@SrTiO3 assemblies for a local compositionally graded relaxor ferroelectric capacitor with enhanced energy storage density and high energy efficiency

Dielectric capacitors with high energy density and low energy loss are of great importance in high power electric and electronic systems. Traditional BaTiO3 (BT) or its solid solutions have been widely explored as high energy density materials owing to their notably high dielectric constants. However, these materials often suffer from significant drawbacks of strong dielectric nonlinearity, low breakdown strength and high hysteresis loss, limiting the energy storage density and energy utilization efficiency. In this study, by using core-satellite structured nanocubic SrTiO3 (ST) decorated BT assemblies, a composite capacitor with enhanced breakdown strength and weaker dielectric nonlinearity was successfully fabricated in contrast with the pure ferroelectric BT ceramic, resulting in elevated energy storage density and high energy efficiency as extracted from the polarization-electric field loops. The mechanism behind the improved electric and dielectric performances was discovered to be the remarkable suppression of grain size owing to the existence of the ST nanocubes and also the ferroelectric relaxor behaviors arising from the local compositionally graded structure due to the controlled sintering and modulated diffusion of Sr. This work provided a new approach for fabrication of dielectric materials with promising high energy density and low loss.

Lead-free BaTiO3–Bi(Zn2/3Nb1/3)O3 weakly coupled relaxor ferroelectric materials for energy storage

Lead-free (1 − x)BaTiO3–xBi(Zn2/3Nb1/3)O3 (x = 0.05–0.20) materials were fabricated via solid-state reactions. A pure perovskite pseudocubic structure is obtained for all compositions. Dielectric measurements reveal an intensified diffusion and relaxor-like characteristics from 5 mol% to 20 mol% Bi(Zn2/3Nb1/3)O3. Weakly coupled relaxor behavior is concluded from the exceptionally high activation energies of ∼0.20–0.22 eV from the Vogel–Fulcher model for x ≥ 0.10, which possibly results in the extremely low dielectric nonlinearity and extra slim polarization–electric field loops. An optimal discharged energy density of 0.79 J cm−3 with a high energy efficiency of 93.5% is achieved at 131 kV cm−1 for x = 0.15, which proves that the BaTiO3–Bi(Zn2/3Nb1/3)O3 material is a promising candidate for high energy storage applications.

First-principles effective Hamiltonian simulation of ABO3-type perovskite ferroelectrics for energy storage application

Dielectric materials with high power density and energy density are eagerly desired for the potential application in advanced pulsed capacitors. Here, we present the first-principles effective Hamiltonian simulation of perovskite ferroelectrics BaTiO3, PbTiO3, and KNbO3 in order to better predict and design materials for energy storage application. The lattice constant, dielectric constant and ferroelectric hysteresis, and energy-storage density of BaTiO3, PbTiO3, and KNbO3 were calculated with the consideration of the effects of temperature and external electric field.