Dielectric materials with high power and energy densities are desirable for potential applications in advanced pulsed capacitors. Computational material designs based on first‐principles calculations provide a “bottom‐up” method to design novel materials. Here, we present a first‐principles effective Hamiltonian simulation of perovskite ferroelectrics, Ba1‐xSrxTiO3, for energy storage applications. The effects of different chemical compositions, temperatures, and external electric fields on the ferroelectric hysteresis and energy storage density of Ba1‐xSrxTiO3 were investigated. The Curie temperature was tuned from 400 to 100 K by doping Sr in the BaTiO3 lattice. At a constant temperature, the ferroelectric hysteresis became slimmer as the Sr content increased, and the energy storage efficiency increased. For the same chemical composition, the energy storage density increased as the temperature increased. For the composition x = 0.4, a discharged energy density of ~2.8 J/cm3 with a 95% efficiency was obtained in an external electric field of 350 kV/cm, and a discharged energy density of 30 J/cm3 with a 92% efficiency was obtained in an external electric field of 2750 kV/cm. The energy storage property predictions and new material designs have potential to create experimental and industrial products with higher energy storage densities.
The strontium titanate (SrTiO 3 ) single crystals with different orientations of (100), (110) and (111) were investigated using thermally stimulated depolarization current (TSDC) measurements, which has been proved to be an effective strategy to fundamentally study the relationship between relaxation phenomena and defect chemistry in dielectrics. The origins of different relaxations in SrTiO 3 crystals were identified and the activation energy of oxygen vacancies was estimated from TSDC measurements. It was further found that oxygen-treated SrTiO 3 crystals exhibit different relaxation behaviors. Noticeable changes of thermal relaxation associated with oxygen vacancies have taken place in relation to the crystalline anisotropy. The SrTiO 3 (110) samples display higher concentration and activation energy of oxygen vacancies. First-principles calculations were carried out on SrTiO 3 (110) crystals to study the effect of oxygen vacancy on different surface microstructure. From the resulting minimum formation energy of 0.63 eV, it demonstrates that the oxygen vacancies tend to form on the TiO-terminated surfaces. Considering the band structure, oxygen vacancies near the surface contribute to the transition of crystal from insulator to metallic characteristic.
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