Electronic structures and ferroelectric properties of ABi 2Ta 2O 9 (A=Ca, Sr, and Ba)

Abstract

The electronic structures of ABi 2Ta 2O 9 (A=Ca, Sr, and Ba) were calculated by using first-principles under optimized structure. As the size of A-site cation decreases from that of Ba 2+ to Ca 2+, the band-gap between O 2p and Ta 5d increases from 2.0 to 2.9 eV, which responses to the stronger orbital hybridizations between Ta 5d and O 2p orbits favoring improvement of the ferroelectric property, decrease in leakage current, and increase in both spontaneous polarization and Curie temperature by the structural distortion. In contrast to CaBi 2Ta 2O 9 and SrBi 2Ta 2O 9, the hybridization between Ba 5p orbits and O 2p orbits in BaBi 2Ta 2O 9 has better structural stability.