Microwave and infrared dielectric response in BaTiO3 based relaxor ferroelectrics

Abstract

AbstractMicrowave (MW), infrared (IR) dielectric response, and Raman spectra of BaZryTi1‐yO3 (BZT) (y = 0.25–0.40) and BaTi1‐zSnzO3 (BTS) (z = 0.15–0.30) ceramics were studied systematically. As the substitution levels increased, the evolution from normal ferroelectric to canonical relaxor was observed. BaTiO3 based relaxor ferroelectrics have high tunability, MW permittivity, and loss tangent. IR analysis confirmed that the relaxor behavior in BZT and BTS was caused by the cationic disorder with BO6 octahedron and the origin of larger diffuseness in BTS dielectric peak was attributed to a distinct split of BO6 bending. Compared with BST, the soft mode in BaTiO3 based relaxor ferroelectrics hardened slightly and became harmonic with increasing substitution levels, resulting in high tunability for BaTiO3 based relaxors. The variation in tunability of BZT with composition is larger than that of BTS, due to the larger variation in softest mode with composition for BZT. Raman scattering showed that, in comparison with cubic‐BST, the bands at ∼730 cm−1 were observed in cubic‐BZT and ‐BTS, owing to the positional disorder at B‐site cation. However, an extra band at ∼770 cm−1 in BZT appeared and red‐shifted, whose intensity increased with the substitution levels increasing. It is of particular interest that the upward shift of A1(TO2) mode of the samples with higher substitution levels indicated a tighter bonding between the cations and the anions, which led to a smaller permittivity of the samples with higher substitution levels.