High frequency dielectric relaxation in lanthanum modified PbTiO3 ferroelectric ceramics

Dielectric measurements of lanthanum modified lead titanate ceramics were carried out in a frequency and temperature range of 70 ´ 10(6)Hz - 2 ´ 10(9)Hz and 300 K - 420 K, respectively. Dielectric relaxation appears around 7 ´ 10(8)Hz at room temperature, and the maximum of the dielectric relaxation was around 393 K, the transition temperature (Tc). The relaxation frequency passes through a minimum at Tc and the dielectric relaxation exists in both paraelectric and ferroelectric phases. A fitting of the experimental data with the Debye relations gives some keys for understanding the dielectric behavior of such materials.