Bismuth layer-structured ferroelectrics with high Curie temperatures have recently attracted significant attention as promising candidates for high-temperature piezoelectric applications. However, the conventional solid-state reaction method entails high-temperature processing that induces bismuth volatilization, thereby degrading device reliability. In this study, we employed a co-precipitation method enabling atomic-level mixing to significantly lower the synthesis temperature of Nb/Tadoped Bi₄Ti₃O₁₂ ceramics compared to the solid-state reaction method. Experimental results demonstrated that the coprecipitation method yielded a pure single phase at 600℃ without intermediate phases. Furthermore, the synthesized nanopowders, with an average size of 100 nm, lowered the onset temperature of sintering shrinkage to 650℃, approximately 200℃ lower than that of the solid-state counterpart. The low-temperature synthesis process proposed in this work is expected to contribute to the performance enhancement of high-temperature piezoelectric devices by effectively suppressing bismuth volatilization and ensuring compositional stability.

This study investigated crystal structures, microstructures, and electric-field-induced strain (EFIS) properties of Bibased lead-free ferroelectric/relaxor composites. Bi_1/2(Na_0.82K_0.18)_1/2TiO₃ (BNKT) as a ferroelectric material and 0.78Bi_1/2(Na_0.78K_0.22)_1/2TiO₃-0.02LaFeO₃ (BNKT2LF) as a relaxor material were synthesized using a conventional solid-state reaction method, and the resulting BNKT2LF powders were subjected to high-energy ball milling (HEBM) after calcination. As a result, HEBM proved a larger average grain size of sintered samples compared to conventional ball milling (CBM). In addition, the increased sintering time led to grain growth. Furthermore, HEBM treatment and sintering time demonstrated a significant effect on EFIS of BNKT/BNKT2LF composites. At 6 kV/mm, 0.35% of the maximum strain (S_max) was observed in the HEBM sample sintered for 12 h. The unipolar strain curves of CBM samples were almost linear, indicating almost no phase transitions, while HEBM samples displayed phase transitions at 5~6 kV/mm for all sintering time levels, showing the highest S_max/E_max value of 700 pm/V. These results indicated that HEBM treatment with a long sintering time might significantly enhance the electromechanical strain properties of BNT-based ceramics.

Piezoelectric actuators, which utilize piezoelectric crystals or ceramics, are commonly used in precision positioning applications, offering high-speed response and precise control. However, the use of low-performance ceramics and expensive single crystals is limiting their versatile use in the actuator market, necessitating the development of both high-performance and cost-effective piezoelectric materials capable of delivering higher forces and displacements. The use of textured Pb (lead)-based piezoelectric ceramics formed by so-called templated grain growth method has been identified as a promising strategy to address the performance and cost issue. This review article provides insights into recent advances in texturing Pb-based piezoelectric ceramics for improved performance in actuation applications. We discussed the relevant issues in detail focusing on current challenges and emerging trends in the textured piezoelectric ceramics for their reliability and performance in actuator applications. We discussed in detail focusing on current challenges and emerging trends of textured piezoelectric ceramics for their reliability and performance in actuator applications. In conclusion, the article provides an outlook on the future direction of textured piezoelectric ceramics in actuator applications, highlighting the potential for further success in this field.

n this paper, in order to develop outstanding Pb-free composition ceramics, the Fe2O3-doped(Na0.525K0.443Li0.037)(Nb0.883Sb0.08 Ta0.037)O3 + 0.3 wt% Bi2O3 + x wt% Fe2O3 (x= 0∼1.0 wt%)(abbreviated as NKL-NST) lead-free piezoelectric ceramics have been synthesized using the ordinary solid state reaction method. The effect of Fe2O3-doping on their microstructure and electrical properties were investigated. XRD diffraction pattern studies confirm that Fe2O3 completely diffused into the NKL-NSTlattice to form a new stable soild solution with Fe3+ entering the Nb5+, Sb5+ and Ta5+ of B-site. And, phase structure of all the ceramics exhibited pure perovskite phase and no secondary phase was found in the ceramics. The ceramics doped with 0.6 wt% Fe2O3 have the optimum values of piezoelectric constant(d33), planar piezoelectric coupling coefficient(kp) and mechanical quality factor(Qm) : d33= 233[pC/N], kp= 0.44, Qm= 95. These results indicate that the (Na0.525K0.443Li0.037)(Nb0.883Sb0.08Ta0.037)O3 +0.3 wt%Bi2O3 + 0.6 wt% Fe2O3 ceramic is a promising candidate for lead-free piezoelectric ceramics.

Eco-friendly (Na, K) Nb03 (NKN)-based piezoelectric ceramic materials were fabricated by conventional ceramic method for shear mode piezoelectric energy harvesting application. NKN-LiTaO3 (LT) based compositions were adopted for the high d15xg15 which is proportional to harvested energy density. The composition 0.935(Na0.535K0.485) NbO3-0.065LiTaO3 was found to be lie on the boundary of tetragonal and orthorhombic phases. With reducing Ta content, the dielectric constant decreased gradually while maintaining high d15, which resulted in increased d15xg15, The composition 0.935(Nao0.535K0.485)) NbO-0.065Li (Nb0.990Ta0.0010) O3 was found to possess excellent piezoelectric and electromechanical properties (d15sxg15 =29 pm2/N, d13 417pC/N, k15= 0.55), and high curie temperature (T 455t).

A bolt-clamped ultrasonic viscometer was designed and fabricated using a pair of ring-shaped piezoelectric ceramic resonators. For its compactness and low operation frequencies, simulation of piezoelectric resonators was carried out using an ATILA program. Ring-shaped resonators using 0.05Pb(Mn1/3Sb2/3)O3-0.95Pb(Zr0.475Ti0.525)O3 ceramics were prepared by a conventional ceramic processing, which were then clamped with a pair of metal caps. The fabricated sensor module with a small volume of less than 1 cm3 and an operation frequency as low as 26.5 kHz showed a good relationship between its quality factor and the viscosity of oil.

Abstract: (K(0.5)Na(0.5)) (Nb(0.96)Sb(0.04)) O(3)+1.2 mol% K(4)CuNb(8)O(23) ceramics doped with iron oxide (Fe(2)O(3)) were prepared by a conventional mixed oxide method. And then, their piezoelectric and dielectric properties were investigated as a function of Fe(2)O(3) addition. X-ray diffraction studies reveal that Fe(3+) diffuses into the NKN lattices to form a solid solution with a pure perovskite structure at room temperature. At the sintering temperature of 1,060℃, when 0.2 mol% Fe(2)O(3) was doped, the piezoelectric constant (d(33)), electromechanical coupling factor (Kp), and mechanical quality factor (Qm) showed the excellent values of 131.67 pC/N, 0.436, and 696.36, respectively. Results show that Fe(2)O(3) deped (K(0.5)Na(0.5))(Nb(0.96)Sb(0.04))O(3)+1.2 mol% K(4)CuNb(8)O(23) lead-free piezoelectric ceramics are a promising lead free material for piezoelectric transformer applications.