Doping effect on the dielectric property in bismuth titanate

The dielectric property complemented by the mechanical measurement (internal friction) in the doped Bi4Ti3O12 [Bi4-xLaxTi3O12 (x=0.5,0.75,1) and Bi4-y/3Ti3-yNbyO12 (y=0.015,0.03,0.06)] was systematically investigated from room temperature to 350 degreesC. In the plot of dielectric loss versus temperature for Bi4Ti3O12 (BiT), a relaxation peak was confirmed to be associated with the motion of the oxygen vacancy. It is found that the La doping at site A is in favor of improvement of the fatigue property, in contrast, the Nb doping at site B can mainly enhance the remanent polarization. Appropriate La doping at site A of perovskite-type unit in BiT enhances the chemical stability of oxygen vacancy by improving the height of the potential barrier for hopping and enhances the mobility of domain by the changing of domain structures. While the Nb doping at site B could induce the distortion of oxygen octahedral and reduce the oxygen vacancy concentration by a compensating effect so that it results in an enhancement of remanent polarization. (C) 2004 American Institute of Physics.