NORMAL POLING AND HIGH POLING OF FERROELECTRIC CERAMICS AND SPACE-CHARGE EFFECTS

Poling treatment of field application below Curie point of ferroelectric ceramics is termed ''normal poling'' and a dc field application above Curie point is termed ''high poling''. When a high poling is performed for BaTiO3 or (Sr, Ba)TiO3, a space-charge polarization (P2 type) in the direction of high poling field and an internal bias field E(-i) with the direction opposite to high poling field are generated. When a ferroelectric sample such as BaTiO3 and Pb(Zr, Ti)O3 are aged at temperatures below T, after normal poling, another space-charge polarization (-P2 type) in the direction opposite to that of the normal poling and the internal bias field E(i) with the same direction as that of normal poling field are generated. In this paper, two kinds of space-charge models in ferroelectric ceramics and related phenomena such as space-charge-stabilized effects on the electromechanical strength, the pseudo-pyroelectric current of high-poled (Sr, Ba) TiO3 and asymmetric polarization reversal caused by the -P2 effects will be reviewed and discussed.