Enhanced spontaneous polarization in Sr and Ca co-doped BaTiO_3 ceramics

摘要

The dielectric and ferroelectric properties of (Ba_xSr_(1-x))_(0.77)Ca_(0.23)TiO_3 ceramics with x = 1 to 0.7 were studied and compared with those of Ba_xSr_(1-x)TiO_3 and Ba_(0.77)Ca_(0.23)TiO_3 ceramics. It has been found that Sr doping of the Ba_(0.77)Ca_(0.23)TiO_3 ceramics causes a drastic decrease of the Curie temperature, just like Sr doping of pure BaTiO_3 ceramics, demonstrating a cell volume effect. However, the (Ba_xSr_(1-x))_(0.77)Ca_(0.23)TiO_3 ceramics with x = 0.9 and 0.8 have larger spontaneous polarization than those of the corresponding Ba_xSr_(1-x)TiO_3 and Ba_(0.77)Ca_(0.23)TiO_3 ceramics, along with sufficient insulating properties. The enhancement of their polarization was explained by the increase of the lattice parameter c/a ratio due to the lattice distortion and strain developed in the ceramics.