Stabilized antiferroelectric phase in lanthanum-doped (Na1/2Bi1/2)TiO3.

Phase transition behaviour of La-modified sodium bismuth titanate ceramics [(Na0.5Bi0.5)1[?]1.5xV0.5xLax]TiO3 (NBLT) was investigated. The two anomalies in er(T) and DSC analysis indicated that lower temperature phase transitions below 200 degC became pronounced with La additions. The polarization relaxation of er(T) and double hysteresis loops showed that the intermediate region between two dielectric anomalies was the antiferroelectric modulated phase. The origin of the modulated antiferroelectric state was discussed in terms of disordering effects of the La ions and cation vacancies. With increasing La content, the long-range symmetry of the dipoles in the ferroelectric phase was disturbed in the intermediate region. The competition between rhombohedral ferroelectric phase and tetragonal paraelectric phase contributed to the formation of a modulated antiferroelectric phase in NBLT ceramics. [ABSTRACT FROM AUTHOR]