The microstructure and dielectric relaxor behavior of BaBi4−xLaxTi4O15 ferroelectric ceramics

Ferroelectric ceramics BaBi4−xLaxTi4O15 (BBLT) were prepared with a solid-state reaction process. The obtained phases were confirmed as the Bi-layered perovskite phase with orthorhombic structure by the X-ray diffraction analysis (XRD). The dielectric relaxation was studied as a function of temperature and frequency. A dispersion of the maximum dielectric constant (ɛmax) appears around the temperature of Tm, which shifts toward higher temperatures with the increase of frequency. The modified Curie–Weiss (CW) law was used to describe the relaxor behavior of BBLT ceramics. The relaxation indication coefficient (γ) was estimated with a quadratic fit of modified CW law. The coefficient firstly increases then decreases with the lanthanum increasing, which indicates that the BBT ceramics changes from relaxor-like ferroelectrics to relaxor ferroelectrics then to relaxor-like ferroelectrics with the lanthanum increasing. The relaxor nature of BBLT ceramics was attributed to the A site cationic disorder and the special relaxor behavior of BBLT ceramics was attributed to the high temperature phase transition by La3+ induced.