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 c 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-pyro-electric current of high-poled (Sr, Ba) TiO3 and asymmetric polarization reversal caused by the -P2 effects will be reviewed and discussed.