Fabrication Of Transparent YAG-based Nanoceramics Through Containerless Solidification And Glass Crystallization

Yttrium aluminum garnet(YAG;Y₃Al₅O₁₂)transparent ceramic is particularly noteworthy due to its importance as a host material in solid state laser,phosphors and scintillators.YAG ceramic possesses superior optical,mechanical and thermal property.However,the current sintering synthetic approach give an extremely harsh requirement on high production cost,complex sintering equipment and processes,high powder quality,which limit their industrial production.Here,we proposed a new synthetic route of YAG transparent ceramic:amorphous crystallization approach.Firstly,the YAG melt is levitated isolatedly by using an aerodynamic levitator with CO₂ laser heating.The undercooled melt under containerless condition is apt to be“frozen”to bulk glass despite of its lacking of network former.The effect of rare earth doping and the composition change of Al/Y ratio on YAG glass forming ability has also investigated.Secondly,highly transparent YAG-based polycrystalline ceramic is obtained by full crystallization from YAG-based bulk glass at the temperature around glass forming temperature?950?¹100??.The effects of heat treatment parameters?temperature,dwell time,heating rate etc.?on phase,microstructure and properities will be analyzed.Remarkably,the resulting YAG-based ceramics present fully dense miceostructure composed of YAG?77 wt%?and?-Al₂O₃?23 wt%?nanocrystals.The size of the nanocrystals can be easily tailored by varying the temperature and duration of the one-step full glass crystallization process.These biphasic ceramics demonstrate high transmittance from the visible up to the near infrared ranges?6?m?,excellent thermal property and mechanical properties,especially higher hardness values than YAG single crystal and transparent ceramics.When doped by Ce³⁺,the YAG-Al₂O₃ ceramic shows great fluorescence properity.The combination of the excellees of this novel YAG-based ceramic material,coupled to its fscile room pressure preparation and expected thermal properties,opens great potential applications in wide optical fields shuch as high power white-light LED,lens material and scintillators.In this paper,we also researched the application of containerless solidification in the field of YAG-Al₂O₃ eutectic directional solidification.Al₂O₃-YAG eutectic composite was firstly prepared using the ontainerlessly directional solidification technique.The crystal growth mechanism was studied using the high temperature gradient?about 10³ K/mm?of the containerless directional solidification technology.YAG-Al₂O₃ eutectics grow with a faceted-faceted growth manner at low growth rate.The growth mechanism changes into nonfaceted-nonfaceted growth manner at a growth rate of 800?m/min,and the DS eutectic showed regular lamellar and fiber eutectic morphology,which has not been reported.