Site occupation of doping La3+ cations and phase transition in Na0.5Bi0.5TiO3-BaTiO3 solid solution

Abstract

The effects of La doping on the ferroelectric properties of 0.92Na0.5Bi0.5TiO3-0.08BaTiO3 (NBT—BT) solid solution have been studied both experimentally and theoretically. The experimental results show that an abnormal ferro-to-antiferroelectric phase transition is induced by La doping in NBT—BT. The first-principles calculations indicate that La3+ cations selectively substitute for the A site in NBT—BT as donors. Furthermore, the computed binding energy reveals that La cations is most likely to substitute Ba2+ or Na+, not Bi3+, at A site as donors in NBT—BT, as supported by our Raman spectra. The ferro-to-antiferroelectric phase transition of La-doped NBT—BT is believed to originate from the lattice aberrance and redistribution of valence electrons, thus strengthening the bonding of A—O, enhancing the hybridization between the A cation d orbital and O 2p orbital, and resulting in the deflection of the polar direction of NBT—BT lattice.