Enhanced spontaneous polarization in Sr and Ca co-doped BaTiO3 ceramics

The dielectric and ferroelectric properties of (BaxSr1-x)(0.77)Ca0.23TiO3 ceramics with x = 1 to 0.7 were studied and compared with those of BaxSr1-xTiO3 and Ba0.77Ca0.23TiO3 ceramics. It has been found that Sr doping of the Ba0.77Ca0.23TiO3 ceramics causes a drastic decrease of the Curie temperature, just like Sr doping of pure BaTiO3 ceramics, demonstrating a cell volume effect. However, the (BaxSr1-x)(0.77)Ca0.23TiO3 ceramics with x = 0.9 and 0.8 have larger spontaneous polarization than those of the corresponding BaxSr1-xTiO3 and Ba0.77Ca0.23TiO3 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. (C) 2007 Elsevier Ltd. All rights reserved.