Ferroelectric ceramics are widely used in capacitors, infrared detectors, resonators, ultrasonic transducers and microelectromechanical systems because they can store electrical energy and convert signals among electrical, mechanical and thermal forms. Adding optical transparency could further extend their use to photoacoustic imaging, optical communication, smart windows and integrated photonics. However, conventional polycrystalline ceramics contain pores, grain boundaries, secondary phases and ferroelectric domains that can scatter or absorb light. Some of the same low-symmetry phases and domain structures that enhance piezoelectric or electro-optic performance may also reduce optical transparency, creating a fundamental trade-off between transparency and functionality.
A research team from Qingdao University and City University of Hong Kong has published a comprehensive review of transparent ferroelectric ceramics. The work was led by corresponding authors Yalin Qin and Yongcheng Zhang from Qingdao University and Shujun Zhang from City University of Hong Kong. Yaqi Wang and Chengwu Li contributed equally as first authors.
The review was published in the Journal of Advanced Ceramics on August 18, 2026.
Rather than treating optical transparency and ferroelectric functionality as separate design targets, the review connects them through a unified structure–property framework. The authors analyze optical loss in terms of intrinsic absorption, surface and interfacial reflection, and microstructure-induced scattering. They then explain how pores, grain boundaries, secondary phases, crystallographic anisotropy and ferroelectric domain walls influence the propagation of light through a ceramic.
A central conclusion of the review is that transparency cannot be optimized independently of electrical and electromechanical performance. Grain refinement, domain engineering and defect control may reduce optical scattering, but they can also alter polarization switching, piezoelectric activity, electro-optic response, leakage current and thermal stability.
"Transparency and ferroelectric functionality are often treated as separate targets, but they are governed by the same multiscale structural features," said Yongcheng Zhang, a professor at Qingdao University and a corresponding author of the review. "Practical progress will depend on co-optimizing optical loss, polarization dynamics, thermal stability and manufacturability, rather than maximizing one performance metric in isolation."
The review focuses on two representative material platforms. Lead-based Pb(Mg1/3Nb2/3)O₃–PbTiO3, or PMN–PT, ceramics can exhibit strong piezoelectric and electro-optic responses, making them attractive for transparent ultrasonic transducers, optical switches and modulators. Their limitations include lead content, relatively low Curie temperatures in some compositions and sensitivity to processing and temperature.
Lead-free (K,Na)NbO3, or KNN, ceramics offer a more environmentally compatible alternative. Although their piezoelectric and electro-optic performance generally remains below that of leading PMN–PT materials, KNN-based ceramics have demonstrated promising combinations of transparency, dielectric energy storage, photoluminescence and photochromism. The review also discusses PLZT, BaTiO₃ and Bi₀.₅Na₀.₅TiO₃-based materials where they provide useful benchmarks or broaden the functional scope.
The authors summarize several strategies for navigating the transparency–functionality trade-off. Pressure-assisted and atmosphere-controlled sintering can remove residual pores and improve optical homogeneity. Grain refinement can reduce scattering when structural features become substantially smaller than the wavelength of incident light. Domain engineering can suppress optically active domain walls while preserving sufficient polarization mobility for piezoelectric or electro-optic responses. Phase-structure tuning can reduce birefringence, while rare-earth doping and defect regulation can modify local polarization, luminescence, photochromism and electrical conductivity.
These strategies must be coordinated rather than applied independently. For example, defects can provide carrier traps that enable photochromic coloration, but excessive defect concentrations may increase optical absorption, leakage current and dielectric loss. Similarly, refining ferroelectric domains may improve transparency, but eliminating too much domain-wall mobility can weaken the electromechanical response.
Representative studies surveyed in the review illustrate the progress of the field. In one lead-based example, Eu-doped 72PMN–28PT transparent ceramics exhibited approximately 68% transmittance at 2500 nm for a 0.4-mm-thick sample, together with a piezoelectric coefficient of about 1400 pC N⁻¹. In a lead-free energy-storage example, a KNN-based ceramic achieved approximately 70% transmittance at 780 nm for a 0.1-mm-thick sample and a recoverable energy-storage density of 7.4 J cm⁻³. The authors emphasize, nonetheless, that data acquired under varying wavelengths, thicknesses, and experimental protocols preclude direct comparisons or rankings. The review organizes the field into five major functional directions: transparent piezoelectricity, electro-optic modulation, dielectric energy storage, photoluminescence and photochromism. These functions could support transparent ultrasonic transducers for photoacoustic imaging, electro-optic switches and modulators for optical communication, transparent energy-storage components, optical and temperature sensors, smart windows, and multidimensional optical information storage.
The authors distinguish between devices already demonstrated using transparent ceramics and benchmark applications based on related single crystals, thin films, glasses or composites. Ceramic-based demonstrations include transparent ultrasonic transducers, electro-optic components and optically responsive information-storage materials. Some high-performance transparent robots, adaptive lenses, smart-window systems and three-dimensional optical-storage devices, however, have been demonstrated using single-crystal, thin-film or glass platforms.
These material forms differ in optical homogeneity, processing route, functional response and device-integration strategy, and their performance should not be treated as directly interchangeable. Instead, the non-ceramic demonstrations are included as benchmarks that may provide transferable design principles for future transparent ceramic devices.
Looking ahead, the review identifies several priorities for moving transparent ferroelectric ceramics from laboratory samples to integrated devices. Machine learning and high-throughput computation could accelerate the screening of complex multicomponent compositions. Texture engineering may align grains along favorable crystallographic directions and help ceramics approach single-crystal-like functional performance. High-Curie-temperature compositions are needed to improve operational stability, while additive manufacturing and scalable sintering may enable larger components and more complex device geometries.
The authors also highlight transparent electrodes, device packaging, long-term cycling reliability and system-level integration as critical but sometimes overlooked issues. Future materials will need to combine optical transmission, functional response, thermal stability, manufacturability and environmental compatibility in a single platform.
By linking optical-loss mechanisms with composition design, microstructure regulation and device requirements, the review provides both a technical reference and a strategic roadmap for the field. It suggests that transparent ferroelectric ceramics are progressing from isolated property demonstrations toward multifunctional components for intelligent sensing, biomedical imaging, optical communication, energy management and integrated photonics. Their broader adoption will depend not only on achieving record performance, but also on reproducible fabrication, standardized optical evaluation and reliable operation under practical conditions.
About the Authors
Prof. Yalin Qin is a faculty member at the College of Physics, Qingdao University, and was previously a visiting scholar at Pennsylvania State University. Her research focuses on the mechanisms, fabrication, and property modulation of transparent piezoelectric ceramics. She has published more than 20 peer-reviewed papers on transparent ferroelectric and piezoelectric materials. Prof. Yongcheng Zhang is a Distinguished Professor and Vice Dean of the College of Physics at Qingdao University. His research focuses on transparent ferroelectric ceramics and their applications in electro-optic modulation, optical communication, ultrasound and photoacoustic imaging. His group has developed prototype electro-optic switches, modulators and transparent ultrasonic transducers. Shujun Zhang is a Chair Professor in the Department of Chemistry at City University of Hong Kong and a Distinguished Professor at the University of Wollongong. He is an internationally recognized expert in dielectric, piezoelectric, and ferroelectric materials and their applications. He is a Fellow of the World Academy of Ceramics, IEEE and the American Ceramic Society.
Funding
This work was financially supported by the National Natural Science Foundation of China (Grant Nos. 52272116 and 12132020), the Taishan Scholar Program of Shandong Province (Grant No. tstp20240511) and the Guangxi Key Technologies R&D Program (Grant No. 2024AB09025).
DOI LINK: 10.26599/JAC.2026.9221343
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 2025 IF is 14, ranking in Top 1 (1/34, Q1) among all journals in "Materials Science, Ceramics" category, and its 2025 CiteScore is 24.6 (6/133) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
