Microwave and infrared dielectric response in BaTiO₃ based relaxor ferroelectrics

Abstract

Microwave (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.

High‐Temperature Dielectric Relaxation Behaviors of Relaxer‐Like PbZrO3–SrTiO3 Ceramics for Energy‐Storage Applications

“…Thep arameter g gave information on the character of the phase-transition behaviors:f or g = 1, an ormal Curie-Weiss law was obtained, whereasac omplete diffuse phase transition wasd escribed for g = 2. [24] Figure 2s hows the plot of ln(1/eÀ1/e m )v ersus ln(TÀT m )w ith af requency of 10 kHz. By fitting the experimental data by using Equation (1), av alue of g = 1.73 was obtained.…”

“…The parameter γ gave information on the character of the phase‐transition behaviors: for γ =1, a normal Curie–Weiss law was obtained, whereas a complete diffuse phase transition was described for γ =2 . Figure shows the plot of ln(1/ ɛ −1/ ɛ m ) versus ln( T − T m ) with a frequency of 10 kHz.…”

Switching Characteristics and High-Temperature Dielectric Relaxation Behaviours of Pb(Zn1/3Nb2/3)0.91Ti0.09O3 Single Crystal

“…The dielectric characteristics of relaxor ferroelectric materials are well known to deviate from the typical Curie-Weiss behavior, and can be described by a modified Curie-Weiss relationship [49]:$1/{\epsilon }_r-1/{\epsilon }_m={false(T-T_{m}false)}^{\gamma }/C_1,1\le \gamma \le 2$where γ and C 1 are assumed to be constant. For γ = 1, a normal Curie-Weiss law was obtained, and a complete diffuse phase transition was described for γ = 2 [50]. The plots of ln(1/ ε r − 1/ ε m ) versus ln( T − T m ) with a frequency of 10 kHz are shown in Figure 4.…”

Manufacture of electrical and magnetic graded and anisotropic materials for novel manipulations of microwaves

“…Common bulk polymers, such as polyethylene (PE) and polypropylene (PP), are readily processed but provide only ε = 2-3 at approximately 10 GHz [10,11], limiting their use in transformation optics devices. On the other hand, while ceramics such as BaTiO 3 are brittle and much less versatile with respect to processing, they have bulk permittivities at microwave frequencies that can be orders of magnitude larger than those of polymers [12,13]. Consequently, by dispersing micro-scale particles of BaTiO 3 in a polymer matrix, processable materials with ε up to 20 in the frequency range 12-18 GHz can be obtained [14][15][16][17][18].…”