# Progress in Transparent Nano-Ceramics and Their Potential Applications
## 5 Other Transparent Nano-Ceramics  
### Electro-Optical Transparent Nano-Ceramics  
The rise of emerging electro-optical materials is in line with the arrival of modern electronic, optical, and laser technologies, which are increasingly demanding materials. Compared with other materials, they have fast speed, low consumption, high reliability, and strong interference suppression ability, which mainly used in transducers, actuators and sensors, and it has a great impact on space structure, electronic industry, etc. [97; 98]. The new electro-optic ceramic material not only has the advantages of ordinary electro-optic materials but also has a fast response speed. The response time is generally only a few nanoseconds, and the electro-optic coefficient is larger than other materials, about 2 \(\times\) 10\({}^{-15}\)\(\sim\)6.6 \(\times\) 10\({}^{-15}\) (m/V)\({}^{2}\). At present, commonly used electro-optical transparent ceramic materials are mainly two types: lead lanthanum zirconate titanate ceramics (PLZT) and lead magnesium titanate-lead titanate ceramics (PMN-PT) [99]. PLZT ceramic is a kind of transparent ceramic with an ABO\({}_{3}\) type perovskite structure. It has strong light transmittance in the visible light to infrared light band. The light transmittance reaches its peak at about 600 nm, 802 nm, and 88 = 0 nm. PLZT ceramics are more commonly used in the manufacture of multi-functional, low-loss optical devices, as well as in holographic storage technology and optical fiber sensing [100]. The PMN-PT transparent ceramic is an ABX\({}_{3}\) type ceramic with a high dielectric constant, which can reach up to 600 at room temperature. Additionally, it has better optical transparency. At the visible light wavelength of 400-2000 nm, the transmittance increases from 0 to 70% and finally stabilizes at 70% when the temperature rises from 400 \({}^{\circ}\)C to 2000 \({}^{\circ}\)C. It has a wide range of applications in satellite communications, sensors, frequency converters, etc. [101]. In 1970, [PERSON] et al. [102] first used the hot-pressing sintering method to prepare opto-ceramics with a thickness of 1 mm. This method could improve the compactness of ceramic materials. The density could reach about 99% of the standard density, and the light transmittance could reach 80%. In 2016, [PERSON] et al. [103] added powders of Bi\({}_{2}\)O\({}_{3}\) and CuO oxides in the process of preparing PLZT ceramics and fired particles with a diameter of 1 cm without agglomeration. It was found that the dielectric constant reached a peak value of 2000 when the temperature increased to 215 \({}^{\circ}\)C, and then the dielectric constant began to decrease with the increase in temperature. After adding the mixture, the sintering temperature was reduced by up to 50 \({}^{\circ}\)C. In 2018, [PERSON] et al. [104] doped Nb and Fe elements during the preparation of PLZT ceramic materials, in which the radius of Fe\({}^{3+}\) was 69 pm, and the radius of Nb\({}^{5+}\) was 78 pm. The results showed that the conductivity increased from 10\({}^{-8}\) to 10\({}^{-6}\) S/cm when the frequency was increased from 100 Hz to 1 MHz at room temperature. When the doping was 2%, the energy storage density reached a maximum of 140 mJ/cm\({}^{3}\). In 2017, [PERSON] et al. [105] prepared PMN-PT ceramics with a thickness of 0.35 mm using a two-step hot-pressing method, in which the contents of lanthanum, PMN, and PT were 3%, 75%, and 25%, respectively. When the measured temperature continued to rise, the half-wave voltage gradually increasedfrom 200 V to 400 V, and the electro-optic coefficient continued to increase. In 2018, [PERSON] et al. [106] reported on the preparation of PMN-PT/CFO thin films by sol-gel spin-coating technology. When the ratio of CFO to PMN-PT was 4:1, the leakage amount reached its maximum. The film quality was improved, and when the temperature increased from 650 \({}^{\circ}\)C to 730 \({}^{\circ}\)C, the leakage current decreased from 97.54 to 40.59. This indicates that the ferroelectric performance improves.