Effect of Ce and La substitution on dielectric properties of bismuth titanate ceramics

Effect of Ce and La substitution on the microstructure and dielectric properties of bismuth titanate (BT) ceramics was investigated. Bismuth titanate ceramics (Bi4−xAxTi3O12) (A = Ce or La; x = 0, 0.5, 1) were processed by sintering of pressed pellets, prepared from nanopowder synthesized by the modified sol–gel method. Pure and La modified bismuth titanate ceramics have single Bi4Ti3O12 phase of Aurivillius type, whereas a small amount of Bi2Ti2O7 pyrochlore phase appears in Ce modified bismuth titanate ceramics. In the same time addition of La and Ce improved sinterability of BT ceramics. The results of the measurement of dielectric constant and loss tangent at different frequencies (100 Hz–1 MHz) as a function of temperature reveal that Ce modified ceramics has a diffuse phase transition. Temperature Tm, corresponding to the maximum value of the dielectric constant, is shifted to higher temperature and the maximum value of the dielectric constant is decreased with increasing frequency, which indicate that relaxor behavior is caused by Ce substitution.