A Research on Delayed Thermal Depolarization, Electric Properties, and Stress in (Bi0.5Na0.5)TiO3-Based Ceramic Composites

Abstract

Depolarization behavior is one of the main shortcomings of (Bi0.5Na0.5)TiO3-based ceramics. Considering the undesirable efficiency of traditional modification methods, in this paper a series of 0–3 type ceramic composites 0.85(Bi0.5Na0.5)TiO3-0.11(Bi0.5K0.5)TiO3-0.04BaTiO3-x mol% ZnO (BNKT-BT-xZnO)) were synthesized by introducing ZnO nanoparticles. The results of the X-ray diffraction pattern (XRD) and energy dispersive spectroscopy (EDS) demonstrate that the majority of ZnO nanoparticles grow together to form enrichment regions, and the other Zn2+ ions diffuse into the matrix after sintering. With ZnO incorporated, the ferroelectric–ergodic relaxor transition temperature, TF-R, and depolarization temperature, Td, increase to above 120 °C and 110 °C, respectively. The research on temperature-dependent P–E loops verifies an attenuated ergodic degree induced by ZnO incorporation. For this reason, piezoelectric properties can be well-maintained below 110 °C. The electron backscatter diffraction (EBSD) was employed to investigate the stress effect. Orientation maps reveal the random orientation of all grains, excluding the impact of texture on depolarization. The local misorientation image shows that more pronounced strain appears near the boundaries, implying stress is more concentrated there. This phenomenon supports the hypothesis that potential stress suppresses depolarization. These results demonstrate that the depolarization behavior is significantly improved by the introduction of ZnO. The composites BNKT-BT-xZnO are promising candidates of lead-free ceramics for practical application in the future.

Large electrostrain achieved in BNKT‐based ceramics by the adjustment of phase boundary with Ba(Sn0.70Nb0.24)O3 addition

“…Additionally, T m gradually decreases, and the dielectric peak broadens with increasing BSN content, signifying that BSN substitution induces a diffusive phase transition. At temperatures surpassing T m , the ceramic samples exhibit pronounced frequency dispersion, 42,43 primarily attributed to the presence of oxygen vacancies within the material. The oxygen vacancies within the ceramics display increased activity at elevated temperatures, leading to a sharp rise in material conductivity.…”

Na1/2Bi1/2TiO3‐based ceramics with increased depolarization temperature and piezoelectric coefficient

“…It was proposed that diffusion of Zn 2+ into the NBT-BT lattice was the main contributor to the inhibition of depolarization behavior. 19 Recently, Zhang et al 20 increased the T d to 110 • C by adding ZnO into the ternary ceramic NBT-KBT. Contrasting the above three methods, chemical doping is a relatively simple method to improve piezoelectric properties, but increasing d 33 of NBT will unavoidably reduce T d , and vice versa.…”

“…It was proposed that diffusion of Zn 2+ into the NBT–BT lattice was the main contributor to the inhibition of depolarization behavior 19 . Recently, Zhang et al 20 . increased the T d to 110°C by adding ZnO into the ternary ceramic NBT–KBT.…”