Ferroelectric properties of BaTiO3-BiScO3 weakly coupled relaxor energy-storage ceramics from first-principles calculations

Highlights: • Ferroelectric properties are achieved from first-principles calculations. • Lattice expansion and an indirect band-gap structure are found. • Strong orbital hybridization of Bi/Ti atoms with O atoms are discovered. • B-site ionic displacement disorder increases with BiScO3 content. • Weakly coupled relaxor behavior from electronic and atomic scale are deduced. -- Abstract: Weakly coupled relaxor ferroelectrics BaTiO₃-BiMeO₃ (Me symbolizes trivalent or averagely trivalent cations) have received growing interest for energy-storage applications due to their extremely low remnant polarizations and slim hysteresis, which therefore provides high energy density and energy efficiency. Although large experimental progress has been made, there is still a lack of theoretical understanding from the electronic and atomic point of view. In this paper, by targeting the prototypical BaTiO₃-BiScO₃ (BT-BS) weakly coupled energy-storage ceramics, we investigated the ferroelectric properties at the electronic and atomic scale using first-principles calculations coupled with a phenomenological theory model. Results show that the lattice volumes expand with the increase of BS content, and an indirect band structure was found for the BT-BS ceramics. Ferroelectric polarizations become reduced and hysteresis loops get slimmer with the addition of BS. Moreover, large ionic displacement disorder of Ti/Sc atoms and strong orbital hybridization of Bi/Ti atoms with O atoms were discovered, which should serve as an origin of the reduced ferroelectric polarization and contribute to the weakly coupled relaxor behavior of the BT-BS ceramics. The employed methods and conclusions in this work should also be applicable to other BaTiO₃-BiMeO₃ ceramic systems, shedding light on the further enhancement of energy-storage performance from the electronic and atomic scale.