The convergence of optics and electronics, driven by intelligent systems and wearable technologies, demands materials that seamlessly integrate optical transparency with robust electrical and mechanical functionalities. Transparent ferroelectric ceramics (TFCs) have emerged as a pivotal platform in this endeavor, uniquely bridging high optical transmittance with strong ferroelectric, piezoelectric, and electro-optic responses. This review comprehensively charts the evolution of TFCs, from fundamental material design to cutting-edge device applications. We systematically analyze the core strategies for achieving transparency in two representative transparent ferroelectric ceramic systems, namely lead-based (Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃, abbreviated as PMN–PT) and lead-free ((K,Na)NbO₃, abbreviated as KNN) systems), while also discussing other important systems such as (Pb,La)(Zr,Ti)O₃ (PLZT), BaTiO₃ (BTO), and (Bi_0.5Na_0.5)TiO₃ (BNT) where appropriate for comparison. Critical mechanisms such as grain and domain engineering, refractive-index matching, phase-structure tuning, and defect control. Representative functionalities—including transparent piezoelectricity, electro-optic modulation, energy storage, photoluminescence, and photochromism—are highlighted, with their potential applications evaluated across photoacoustic imaging, adaptive optics, transparent robotics, smart windows, and optical communication. Finally, we identify key challenges and future opportunities, such as high Curie temperature (T_c) design, texture engineering, and multifunctional co-integration. Overall, this review aims to provide theoretical insights and material-design foundations for next-generation multifunctional transparent ferroelectric devices, accelerating their adoption in intelligent sensing, integrated photonics, and transparent optoelectronic systems.

Porous piezoceramics are attractive for high-sensitivity sensing and energy conversion due to their low density, reduced dielectric constant (ε_r), and good mechanical compliance. However, increasing porosity is often accompanied by a significant reduction in the piezoelectric charge coefficient (d₃₃), creating an intrinsic trade-off that limits the practical use of porous structures in high-sensitivity piezoelectric devices and leaves their overall performance advantages under debate. In this work, we overcome this challenge by developing a fully open-cell, three-dimensionally interconnected Pb(Zr_1/2Ti_1/2)O₃–Pb(Zn_1/3Nb_2/3)O₃–Pb(Ni_1/3Nb_2/3)O₃ (PZT–PZN–PNN, PZNNT) porous piezoceramic (3D-PPC). Despite an ultrahigh porosity of 92%, the material maintains a high d₃₃ of approximately 470 pC/N, approximately 90% of that of the dense ceramic. The effective ε_r is reduced to approximately 140 (a 94% decrease), leading to an approximately 14-fold enhancement in the piezoelectric voltage coefficient g₃₃ (approximately 380×10⁻³ Vm/N). Combined microstructural characterization, domain analysis, defect studies, and multiphysics simulations show that the exceptional performance arises from synergistic effects of heterogeneous stress and electric fields, multiscale domain structures, and defect-mediated regulation within the three-dimensionally interconnected porous architecture. Finally, the material generates peak output voltages up to 200 V under subtle mechanical excitation and achieves an ultrahigh sensitivity of 38.7 V/kPa. These results show that three-dimensionally interconnected porous architectures are not merely passive means of reducing dielectric permittivity but also active structural strategies for tuning local fields and polarization behavior.

Ferroelectric materials are highly promising for next-generation electro–optic (EO) modulators because of their ultrafast and efficient light modulation. However, efforts to maximize polarization freedom for large refractive index modulation—through domain engineering, epitaxial strain, and defect engineering—have hit limitations, leaving intrinsic polarization mechanisms largely unexplored. Here, we report a giant effective EO coefficient (~233.5 pm/V) in PbZr_0.52Ti_0.48O₃ (PZT) films, which surpasses all reported values measured under an in-plane electric field and significantly exceeds the theoretical limit (~13 pm/V) as well as the value of LiNbO₃ (~31 pm/V). Beyond conventional domain switching, phase transitions and domain wall variations critically enhance the EO effect. The highly relaxed structure of the PZT film, with mixed [001] and [100] orientations and disordered nanoscale phases, enables unprecedented polarization control. This unique configuration breaks the theoretical EO coefficient limit, bridging the gap between predictions and experimental results. Owing to its high Curie temperature and compatibility with wafer-scale fabrication, PZT has emerged as a promising candidate for next-generation high-performance EO modulators. Our findings not only advance the frontiers of ferroelectric EO materials but also pave the way for exploring other ferroelectric thin-film devices, such as those for energy storage and electrocaloric cooling, by leveraging enhanced polarization modulation mechanisms.