Transparent electro-optic (EO) oxide ceramics are known for their rapid EO effects. EO ceramics have several advantages over single-crystals, including variable size and shape, controllable chemical composition, superior mechanical properties, and low cost. Synthesis of high-performance transparent EO ceramics requires high purity of raw materials, high density, homogeneous composition, uniform grain size, and relatively wide bandgap. Powder synthesis and sintering are two of the critical steps involved in the fabrication of highly transparent EO ceramics. Using high-activity precursor powders has been effective in fabricating high-density ceramics that demonstrate excellent EO performance. The sintering process plays a crucial role in achieving this result, and currently, there are several sintering methods available for producing high-density ceramics, including hot-pressing, hot isostatic pressing, and spark plasma sintering. This review summarizes the recent progress in materials and processes used to develop transparent EO ceramics, including those based on lead zirconate titanate, lead magnesium niobate-lead titanate, and lead-free potassium sodium niobate. In addition, several novel applications of transparent EO ceramics, including light shutters, spectral filters, optical memory, as well as image storage and displays are reviewed. In the end, the review concludes with a discussion of future trends and perspectives.
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In this study we fabricated, for the first time, magnesium gallate (MgGa2O4, a partially inverted spinel) transparent ceramics, both undoped and doped with 1 at% Ni. The specimens were derived from in-house prepared powder, with a crystallite size of ~10 nm (by wet chemistry) and densified by pulsed electric current sintering (PECS; peak temperature 950 ℃ for 90 min). Densification levels of 99.84% and 99.52% of theoretical density were attained for doped and undoped materials, respectively. Doping with Ni was seen to marginally improve the densification level. Quite transparent specimens were produced: the best showing transmission of ~89% of the theoretical level (thickness t = 0.85 mm). The absorption spectra revealed that the dopant was accumulated as Ni2+ in the octahedral sites of the lattice, as occurs in single-crystal specimens. After excitation at 980 nm, the doped disks exhibited a wide fluorescence band centered at 1264 nm.