Fabrication of Nd:YAG transparent ceramics using powders synthesized by citrate sol-gel method

The highly transparent Nd:YAG ceramics were prepared by using powders synthesized by citrate sol-gel method. The citrate sol-gel method could avoid defects of the solid-phase reaction method and the liquid phase co-precipitation method in preparing Nd:YAG ceramic powders with the ratio of (Nd³⁺, Y³⁺):Al³⁺ equal to 3:5. The dried gel was the three dimensional net-shaped porous structure. When the dried gel was calcined at 500 °C in oxygen, pure YAG phase formed directly with no intermediate phases. The Nd:YAG powders calcined at 800 °C had maximum particle size near 500 nm. These powders were not equiaxed and there were dumbbell-like and annular grains. The highly compact Nd:YAG ceramics could be well sintered at 1750 °C for 12 h in vacuum atmosphere, and these sample had the average grain size about 3.8 μm. The polished Nd:YAG ceramics was highly transparent, and the transmittances at 1064 nm and 400 nm were 83.4% and 74.2%, respectively. The fluorescence emission spectrum implied high possibility of realizing laser output at 1064 nm by pumping at 808 nm. Generally, the citrate sol-gel method was also a reliable choice for preparing high quality Nd:YAG transparent ceramics.