Using commercial aluminum chloride and yttrium chloride as raw materials, YAG nanopowder was synthesized by using the co-precipitation method. YAG transparent ceramics were prepared through high-temperature vacuum sintering from the nanopowder. Thermogravimetry-differential thermal analysis (TG-DTA), Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and other methods were used to study the effects and rules of chlorine salt concentration and dispersant PEG-6000 concentration on phase formation, particle size, and crystal grain size. With mixed solution of 0.25 mol·L^-1 AlCl₃·6H₂O and 0.15 mol·L^-1 YCl₃·6H₂O as the reactant, 1.0 mol·L^-1 NH₄HCO₃ as the precipitant, and 20 g·L^-1 PEG-6000 as the dispersant, the YAG powder obtained by calcining the precursor at 1100 ℃ for 6 h using the reverse titration coprecipitation method has optimal performance, with an average particle size of 66 nm. The resultant YAG ceramics had linear transmittances of 45.0%@400 nm and 52.8%@1100 nm (1 mm thickness), which need to be further optimized

A₂B₂O₇ system compounds, which usually present three phase structures mainly based on the ionic radius ratios of r_A and r_B (r_A/r_B), have been studied for potential applications in many fields, such as thermal barrier coatings, luminescence powders, fast-ion conductors, photocatalysts, and matrices for immobilization of highly active radionuclides. Since 2005, La₂Hf₂O₇ was fabricated into transparent ceramics and much more attentions were paid on A₂B₂O₇ transparent ceramics for new applications. In this review, the development of A₂B₂O₇ system transparent ceramics was described. The structure characteristics, powder synthesis method, and sintering techniques of the final A₂B₂O₇ transparent ceramics were summarized. After that, the mostly reported A₂Hf₂O₇, A₂Zr₂O₇, and A₂Ti₂O₇ system transparent ceramics were systematically introduced. The potential application fields and future development trends were also discussed, focusing on scintillators, optical elements, and other luminescent materials.