In the realm of pulse power capacitors, dielectric energy storage materials are undeniably the "heart." As global demand surges for rapid charge-discharge capabilities, high operating voltages, and long service lives, these materials play a pivotal role in sectors ranging from hybrid electric vehicles to high-energy weapon ignition systems.
However, Barium Titanate (BaTiO3, or BT), the poster child for lead-free ferroelectrics, faces a classic trade-off. While blessed with high polarization strength, it has long been plagued by a "shortcoming": low breakdown strength (typically Eb<1000 kV cm−1).
It is akin to a "seesaw" dilemma: achieving high energy storage density often comes at the expense of breakdown strength, while striving for high voltage tolerance can lead to insufficient polarization. Consequently, the key scientific hurdle for researchers is how to actively construct functional nanodomain structures within the BT system while maintaining its high polarization performance.
The team published their work in Journal of Advanced Ceramics on April 14, 2026.
The Strategy: A "Duet" of A/B-site Co-doping
To break this deadlock, the team led by Prof. Guo Limin from Beijing University of Posts and Telecommunications and Asst. Prof. Zhao Peiyao from Tsinghua University carved out a new path. Using a conventional solid-state reaction method, they successfully fabricated a series of (1−x)BBT−xSLTT ceramics. Rather than adjusting a single component, they deployed a "combo move" of A/B-site multi-ion co-doping, aiming to achieve a comprehensive leap in macroscopic performance through fine-tuned microstructural engineering.
1. A-site Modulation: Breaking Long-range Order to Introduce "Polar Nanoregions"
The team introduced Bi, Sr, and La ions at the A-site. This strategy acted like a stone tossed into a calm lake, successfully disrupting BT's rigid long-range ordered polarization structure. This "perturbation" induced the coexistence of Cubic (C), Tetragonal (T), and Rhombohedral (R) phases and catalyzed the formation of Polar Nanoregions (PNRs). Acting like countless tiny "elastic storage units," these PNRs not only significantly reduced remanent polarization but also endowed the material with superior relaxor characteristics.
2. B-site Modification: Lattice Contraction to Build an "Insulation Fortress"
At the B-site, the introduction of Ta ions utilized their smaller ionic radius to trigger lattice contraction. This lattice distortion further promoted the formation of nanoscale polar clusters and lowered the polarization switching barrier. More critically, this multi-ion doping design significantly increased the grain boundary activation energy. Much like building a high wall at the grain boundaries, this effectively impeded carrier migration, thereby drastically boosting the material's breakdown strength.
Key Findings: A Resonance of Micro and Macro
Experimental results perfectly validated this design philosophy, transforming the "dual role" seen in other systems into a powerful "synergistic effect" of multi-ions:
Micro-characterization: Visualizing "Nanoclusters"
HAADF (High-Angle Annular Dark-Field) characterization clearly captured polar clusters (PNRs) ranging from 1 to 3 nm in size, exhibiting random polarization orientations. Despite being in a relaxor state, the material maintained strong local polarization (with an average atomic displacement of 14 pm), which is the microscopic source of its high energy storage density. XRD and Rietveld refinement further confirmed that the 0.95BBT-0.05SLTT sample exhibited C/T phase coexistence, with significant lattice contraction observed as doping increased.
Macro-performance: Shattering Records
Under an ultrahigh electric field of 1150 kV cm-1, the 0.95BBT-0.05SLTT ceramic exhibited extremely slim P-E hysteresis loops, indicating minimal energy loss. Ultimately, the material achieved an ultrahigh energy storage density of 15.3 J cm-3 and an efficiency of 82.4%.
Power Characteristics: Lightning-fast Charge/Discharge
Beyond "storing a lot," it can also "release fast." Under an electric field of 500 kV cm-1, the discharge time (t0.9) was merely 15 ns, achieving a high current density of 890 A cm-2 and an ultrahigh power density of 223 MW cm-3. This ultrafast capability makes it promising for pulse power applications.
Conclusion and Outlook
Through an A/B-site multi-ion co-doping strategy, this work ingeniously leveraged the mechanisms of polar nanoregion modulation and enhanced grain boundary activation energy to solve the long-standing challenge of balancing high energy storage density with high breakdown strength in lead-free dielectrics. This achievement provides a highly promising candidate for the next generation of eco-friendly pulse power capacitors and offers a new paradigm for the functional design of perovskite structures.
About Author
Limin Guo received her Ph.D. in 2013 from the State Key Laboratory of New Ceramics and Fine Processing at Tsinghua University, under the supervision of Academician Longtu Li. From 2015 to 2017, she conducted postdoctoral research at the University of Central Florida in the United States. As the first or corresponding author, she has published over 50 academic papers in top-tier journals such as Nature Communications, Energy & Environmental Science, and Advanced Functional Materials. Her work has garnered over 3,800 citations, with an h-index of 35.
Funding
The work was supported by the National Natural Science Foundation of China (No. 52372101, 52472130, 52502139), Fundamental Research Funds for the Beijing University of Posts and Telecommunications (Grant 2025JCTP05), Fundamental Research Funds for the Central Universities (Grant 530524002), Tsinghua University State Key Laboratory of New Ceramic Materials Project (2025QHTC-ZZKYB002).
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
