A Study On The Preparation And Sintering Of YAG Powders

Yttrium aluminum garnet, YAG for short, has become the most commonly used laserhost for its superior physical and chemical property, However, the preparation process ofYAG single crystal is complicated. Transparent Nd:YAG polycrystalline ceramic was used tosubstitute for YAG single crystal to realize laser output. Hence, the research on YAGpolycrystalline ceramic has important practical significance.Solid-phase method is the most conventional way to synthesize YAG powder. But itbears many disadvantages including high reaction temperature and hard elimination of thegenerated intermediate. We carried out the solid-phase reaction using the mixture of transitionalumina, obtained from low-temperature calcination of aluminium hydroxide, and yttria, andmineralizer AlF3as reaction material system. Particle size distribution analysis, XRDdetection and SEM analysis were performed to research the influence of material activity, ballmilling process, mineralizer and calcination process on particle size, morphology and phase ofthe reaction product.The results show that, pure-phase YAG powders can be obtained by calcining aluminumhydroxide at500℃for30h, adding6wt%of AlF3, mixing with Y₂O₃at n（Y）:n（Al） ratio of3:5, ball milling for10h with anhydrous ethanol as dispersion medium at ball/material ratioof15:1, calcining at1,200℃, and holding for3h. The YAG grain with regular morphologycan be produced by calcining aluminum hydroxide at440℃for10h, mixing with Y₂O₃underball milling, adding6wt%of AlF3, and calcining at1,400℃for3h.We also performed experiment of sintering of YAG powder prepared under differentconditions and subjected to cold-press forming, and explored the influence of YAG powderperformance and sintering technique on the density of YAG ceramic through the analysis ofdensity and grain morphology of sintered body. The effects and action mechanism of sinteringaid in the sintering process were further discussed. And, we carried out kinetic analysis on thesintering process, thus achieving kinetic equation of sintering initial stage and kineticequation between sintering temperature and volume density.