Emergence of reentrant relaxor behavior with enhanced electromechanical and electrocaloric effect in Ba0.95Ca0.05Sn0.09Ti0.91O3 ceramic

Abstract

Both A- and B-site-substituted BaTiO3 ceramics are promising alternative relaxor materials to replace lead zirconium titanate as an actuator. With a motivation to improve electromechanical properties, a lead-free Ba0.95Ca0.05Sn0.09Ti0.91O3 (BCST) ceramic close to the polymorphic phase boundary composition is synthesized by solid-state reaction. X-ray diffraction and Raman spectroscopy confirm the coexistence of orthorhombic (Amm2) and tetragonal (P4 mm) phases at room temperature. Our low-temperature dielectric study reveals the appearance of a reentrant relaxor state from the ferroelectric state near ∼150 K and is attributed to the coexistence of short and long ferroelectric ordered regions and slowing down of domain dynamics in the smaller regions, similar to the reentrant spin glass state observed in the system Fe-xAu. This feature is confirmed through glass model fitting parameters [ωo = 2.66(±0.28) × 108 Hz, Tg = 110(±1) K, zv = 4.5(±0.3)], and Mydosh parameter (“K” ∼ 0.05). The field-induced polarization (P–E) and strain (S–E) curves show well-defined slim ferroelectric and “butterfly-like” loops with a large value of maximum strain of ∼0.12%, an electromechanical coefficient of d*33 ∼ 1113 pm/V, and an electrostrictive coefficient of Q11 ∼ 0.048 m4/C2 at room temperature.

Feasible Way to Achieve Multifunctional (K, Na)NbO3-Based Ceramics: Controlling Long-Range Ferroelectric Ordering

“…To evaluate the dielectric relaxation characteristic of ε ″ around room temperature, the Vogel–Fulcher fitting is performed using the following formula where f is the measurement frequency, f 0 is the attempt frequency, E a is the activation energy, k is the Boltzmann constant, T m is the temperature corresponding to the maximum ε ″ near T O–T or T R–O&O–T , and T VF is the freezing temperature. , Interestingly, the relaxation behavior of ε ″ at T O–T or T R–O&O–T is well-fitted via the Vogel–Fulcher law for the ceramics with x = 0.04–0.08 (Figure b1–b4 and S5b). Here, the dielectric relaxation behavior occurs far below T C , suggesting a re-entrant-like relaxation. , In particular, here, the re-entrant-like relaxation behavior coexists with the FFP transition (i.e., the multiphase coexistence region) where the lattice is susceptible to the external stimuli (e.g., electric field, temperature, and stress) due to the flexible polarization rotation among different ferroelectric phases, differing from the situation of typical re-entrant relaxors. , …”

“…Here, the dielectric relaxation behavior occurs far below T C , suggesting a re-entrant-like relaxation. 44,45 In particular, here, the re-entrant-like relaxation behavior coexists with the FFP transition (i.e., the multiphase coexistence region) where the lattice is susceptible to the external stimuli (e.g., electric field, temperature, and stress) due to the flexible polarization rotation among different ferroelectric phases, differing from the situation of typical re-entrant relaxors. 46,47 With the increasing x, f 0 and E a first decrease and then increase, while T VF first increases and then decreases (Figure 6c,d).…”

High Energy Storage Efficiency and Electrocaloric Effect in Pb-Free Ba0.85Ca0.15Hf0.10Ti0.90O3 Ceramics for Sustainable Green Energy Applications

“…As a result, relaxor ferroelectrics are the ideal option for EC effect-based refrigeration and energy storage devices (5,26,31). The energy barrier of polarization rotation is lowered when more than one phase is present, resulting in large EC values and significant polarization changes (32).…”