Transparent ferroelectric ceramics: From multifunctional coupling to optoelectronic integration

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 (EO) 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 include grain and domain engineering, refractive-index matching, phase-structure tuning, and defect control. Representative functionalities—including transparent piezoelectricity, EO modulation, energy storage, photoluminescence, and photochromism—are highlighted, with their potential applications evaluated across photoacoustic imaging (PAI), 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.