Changes in structure and phase transition behavior were investigated for two types of La-doped sodium bismuth titanate ceramics. When A-site vacancies were formed by La incorporation, the phase transition near 200C became pronounced. Hysteresis loop and other data demonstrated that the structure above 200C was the incommensurate antiferroelectric phase. In contrast, B-site vacancies produced by La doping do not contribute to the incommensurate phase. The origin for the formation of the incommensurate antiferroelectric state between the rhombohedral ferroelectric phase and tetragonal para-electric phase was explained in terms of decoupling effects due to the A-site vacancies.

Dependence of Incommensurate Phase Formation on Vacancy Type in La-Doped (Na1/2Ba1/2)TiO3. J.K.Lee, J.Y.Yi, K.S.Hong: Journal of Applied Physics, 2004, 96[2], 1174-7