Lead‑based piezoelectric ceramics have long dominated precision displacement actuators due to their excellent electromechanical properties. However, mounting environmental regulations are driving the urgent search for high‑performance lead‑free alternatives. Among them, BiFeO 3 ‑BaTiO 3 (BF‑BT) system is attractive for its high Curie temperature and good ferroelectricity. Nevertheless, its practical application has been severely limited by high leakage currents and poor reproducibility, mainly arising from the thermodynamic instability of BiFeO 3 between 447 °C and 767 °C, which leads to secondary non‑ferroelectric phases, as well as bismuth volatilization and oxygen vacancies.
Now, a team led by Professor Bo‑Ping Zhang at the University of Science and Technology Beijing (USTB) has developed a novel one‑step sintering method that overcomes these long‑standing challenges. Instead of conventional multi‑step solid‑state reactions, the new approach integrates binder removal, pre‑sintering, and sintering into a single heat treatment. By using BaTiO 3 directly as a starting material, the process bypasses the thermodynamically unstable temperature window of BiFeO 3 , effectively suppressing the formation of impurity phases and significantly widening the processing window.
“One‑step sintering method not only simplifies the fabrication process but also dramatically improves the reproducibility and performance of BF‑BT ceramics,” said Prof. Zhang, whose research focuses on lead‑free piezoceramics and thermoelectric materials. Based on this method, the team designed and fabricated a series of 0.7BiFe 1+ x O 3 ‑0.3BaTiO 3 (BF 1+ x ‑30BT) ceramics with a wide range of Fe non‑stoichiometry (‑0.05 ≤ x ≤ 0.05). This extreme non‑stoichiometry design amplifies defect effects, allowing systematic investigation of defect evolution and its impact on macroscopic properties.
Through detailed defect and electrical testing analyses, the team verified the leakage conduction mechanism from room temperature up to near the Curie temperature. Near room temperature, holes are the main charge carriers, whose concentration is directly related to oxygen vacancies. At high temperatures (>300 °C), oxygen vacancies themselves become the dominant carriers, and their pinning by defect dipoles determines the leakage level.
The study also revealed interesting changes in strain behavior before and after poling. Before poling, the sample with x = ‑0.05 exhibited strong bipolar strain asymmetry, which gradually diminished with increasing x value. After poling, all ceramics showed bipolar strain asymmetry, but with a different trend. During poling, space charges redistribute at grain boundaries, generating an additional internal bias field. For the composition with x = 0, this poling‑induced internal field showed the largest increase, causing the most significant change in bipolar strain asymmetry. However, the strong pinning orientation of defect dipoles after poling reduced the unipolar strain, revealing a dual regulation potential of poling treatment for different application scenarios.
“The combination of high d 33 of 201 pC/N and a Curie temperature as high as 501 °C exceeds most reported BF‑BT systems and outperforms other lead‑free families such as KNN‑based and BNT‑based piezoceramics,” added Prof. Zhang. The team also highlights that the superior comprehensive performance – including a high‑field d 33 * of 1021 pm/V and a strain of 0.38% at room temperature – is stably output across a wide range of Fe stoichiometry variations, further demonstrating the robustness of the one‑step sintering method.
About Author
Bo-Ping Zhang is a professor at the School of Materials Science and Engineering, University of Science and Technology Beijing (USTB), China. She received her M.S. and Ph.D. from Tohoku University, Japan, in 1990 and 1993, respectively. Her research interests include lead‑free piezoelectric ceramics and devices, thermoelectric materials and devices, and ferroelectric physics. She has published over 320 scientific papers with an H‑index of 46, and holds 77 Chinese patents and 2 Japanese patents.
Funding
This work was supported by the Basic Science Center Project of the National Natural Science Foundation of China (Grant No. 52388201), the National Natural Science Foundation of China (Grant No. 52302211), and the Fundamental Research Funds for the Central Universities (Grant No. FRF-TP-24-005A).
DOI Link:
https://doi.org/10.26599/JAC.2026.9221302
About Journal of Advanced Ceramics
Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen . JAC’s 2024 IF is 16.6, ranking in Top 1 (1/34, Q1) among all journals in “Materials Science, Ceramics” category, and its 2024 CiteScore is 25.9 (5/130) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
Journal of Advanced Ceramics
Ultra-high piezoelectric properties of BiFeO3–BaTiO3 lead-free piezoelectric ceramics enabled by a one-step sintering process
21-Apr-2026