Aging behavior in Co doped barium titanate ceramics

BaTiO
3
ceramics were doped with acceptor metallic ions (Co, Mn, Fe) and co-doped with Co and Nb. Piezoelectric ceramics were prepared using conventional solid-state reaction. Addition of Li
2
O sintering aid allows obtaining dense ceramics at low sintering temperature. Doping with Co acceptor leads to significant improve of piezoelectric properties but induce distorted and shifted hysteresis loop due to the presence of internal bias field. Field cooling poled ceramics are in the aged state just after poling. Increasing acceptor dopant concentration increases the internal bias field while co-doping with donor (Nb) reduces it. The data are consistent with presence of defect dipoles formed by acceptor substituted in B site and oxygen vacancy of BaTiO
3
tetragonal structure. Alignment of defect dipoles along driven electric field was observed through low frequency switching or cycling. Aging behaviors of unpoled and poled ceramics process were investigated through the study of hysteresis loops and reveal that charge compensation is not complete