Conventional materials generally have a relatively simple function, and it is difficult to meet the requirement of multi-functional materials in modern information society. It is necessary to develop multi-functional, high-sensitivity materials and devices. Transparent ferroelectric ceramic is an advanced multi-functional material, and it can couple optical functions with mechanical, electrical, and acoustical functions, becoming a research hotspot in materials engineering. Based on the performance characteristics and applications of transparent ferroelectric ceramics, they are divided into five categories, i.e., transparent piezoelectric ceramics, transparent electro-optic ceramics, transparent energy storage ceramics, transparent luminescent ceramics, and transparent photochromic ceramics. Recent efforts are made in the research of multifunctional transparent ferroelectric ceramics.

High-performance electro-optical devices are developed based on the electro-optical effect of transparent ferroelectric ceramics, and applied to high-speed optical communication and high-power laser modulation. High-performance transparent transducers can be developed based on their piezoelectric effect and applied to medical photoacoustic imaging, transparent robots, and other fields. As a dielectric material, transparent ferroelectric ceramics can achieve a high dielectric energy storage performance, which has a great application potential in transparent supercapacitors, transparent photovoltaic windows, and transparent energy storage coatings. Transparent ferroelectric ceramics also exhibit good photoluminescence and photochromic properties and can be used in transparent information storage devices, 3D optical information storage, fluorescent labeling, multi-level encryption, transparent sensors and displays, smart windows, and other optoelectronic devices. Research work on multifunctional transparent ferroelectric ceramics give tremendous opportunities for innovation in information technology, medical and health care, new energy, smart technology, etc..

Rare-earth elements (La, Sm) doped Pb(Mg_1/3Nb_2/3)O₃-12PbTiO₃ (PMN-PT) transparent ceramics have superior electro-optic outstanding electro-optic properties (i.e., high transmittance of 70%@NIR, large electro-optic coefficient of 66×10^-16 m²/V², low half wave voltage of 113 V and fast response speed of 10-100 ns). High-performance electro-optical devices, such as electro-optic switches, Q switches, variable optical attenuators, and tunable optical filters, are developed and commercialized. They can be used in free-space optical communication, dual-channel optical communication with continuous adjustment of laser intensity ratio, and continuous control of laser polarization state.

Eu-doped PMN-PT transparent ferroelectric ceramics exhibit a high transmittance (i.e., T=68%) and a superior piezoelectricity (i.e., d₃₃=1400 pC/N), which are greater than those of other transparent piezoelectric ceramics,. The high-performance transparent piezoelectric ceramics have promising application prospects in biomedical photoacoustic imaging, transparent robotics, and transparent loudspeakers. Er-doped and Pr-doped PMN-PT transparent ferroelectric ceramics are proven to have the superior properties in luminescence at visible and near-infrared wavelengths. Furthermore, the fluorescence intensity is linearally related to temperature, indicating a potential application of transparent luminescent ceramics in illumination and optical temperature sensors.

(K_0.5Na_0.5)NbO₃(KNN) based transparent ferroelectric ceramics exhibit a high transmittance (i.e., T of 69%) and a high energy storage density (i.e., 7.4 J/cm³), a large energy storage efficiency (i.e., 74%), and a great breakdown field strength (i.e., 750 kV/cm). This has a potential for application in high-voltage transparent pulse capacitors. Element-doped KNN transparent ceramics also have good photochromic properties. For instance, the maximum luminescence modulation ratio (ΔR_L) reaches 92.6% in Tb-doped KNN transparent ceramics, and the maximum transmittance modulation ratio (ΔR_T) is 70% in Er-doped KNLN transparent ceramics. At present, the storage life of optical information in KNN-based transparent ceramics prolongs to more than 7 d, indicating that it has a potential application in optical information storage.