Modification Of YAG Powders And The Preparation Of YAG Polycrystalline Ceramics

Yttrium Aluminum Garnet (YAG) is an important host material of solid-state laser device. Generally YAG can be made of YAG single crystal or YAG polycrystalline ceramics. The preparation of YAG polycrystalline ceramics have many excellent feature that YAG single crystal do not have, so many researchers begin to prepare YAG polycrystalline ceramics. This text mainly focuses on the modification of YAG powders and using them to prepare ceramics.The modification of the YAG powders is to get the excellent sintering performance powders. The optical performance of YAG powders standard:powders are nearly spherical, high purity, better dispersion. The methods are based on solid-state reaction that using single factor and orthogonal experiments to achieve. The orthogonal experiment changes the amount of dispersant ethanol, milling time, the mineralizer AIF3amount, calcined temperature and time to take four-level-experiment. The characterizations of the powders mainly use XRD patterns, SEM images and particle size distribution diagrams. The results are digitally quantified and arrange. The optical performance of YAG powders conditions:ethanol is7.5ml, the dosage of AIF3is6wt%, the milling time is8h, calcined temperature is1200℃, and calcined time is5h.The Y2O3and A12O3are mixed and sintered especially at1200℃,13OO℃,1400℃for0.5-4h. The solid-state reaction mechanism is studied. The YAG conversion is calculated by XRD patterns and Linear fit the equation a-t of the kinetics models. The kinetics model can be got:when the temperature is1100℃, there is no YAG appears, when1200℃, the rate-determing step is three-dimensional diffusion. When1300℃and1400℃, the main process is nucleating and growing, the generation of YAG is76.94wt%.The preparation of YAG polycrystalline ceramic mainly explore the YAG sintering performance upon different ingredients way, the sintering temperature, the molding way and pre-sintering temperature. And the sintering performance is studied by the linear shrinkage, density and grain size. The density of YAG ceramic is higher when using the ingredients (3). And the density is increased as the sintering temperature is higher. Also the density of YAG ceramic obtained at the cold isostatic pressing is higher than that using dry pressing. At the base of cold isostatic pressing,1200℃is the most suitable temperature to get the highest density.Next YAG polycrystalline ceramics sintering kinetics are discussed. The initial stage of sintering begins at1400℃, the grains start to contact with each other and fuse to form sintered necks, the volume diffusion is the behavior of this period. When1500℃, the grain boundary begins to dissolve and precipitated, the moving of grain boundary is the control speed step. When come to1600℃, the system came in the final stage of sintering. At this time the control speed step is the grain growth which meets its model.