Dielectric and pyroelectric characteristics and ferroelectric soft modes in PbTiO 3 polycrystals doped with Ca 2+

The effects of Ca 2+ ions on the structure and dielectric and pyroelectric characteristics of PbTiO 3 polycrystals were investigated. With increasing content of Ca, a decrease in tetragonal axial ratio ( c/a ) was observed as a consequence of shrinkage of the lattice parameter c . The dielectric constant and pyroelectric coefficient increase and Curie temperature ( T C ) shifts toward lower temperature with increasing content of Ca. The theory of ferroelectric soft mode has been developed to illuminate the relationship between the structure and properties of the polycrystal.