Preparation And Properties Of High Temperature Infrared Transparent AlON Ceramics

High temperature infrared-transmitting AlON ceramics is one of the most promising high temperature infrared-transmitting materials,because of its outstanding optical,mechanical and physical chemical properties.As the key optical device of the infrared seeker missile,it is also a very important defense and military materials.In this paper,we set the target to obtain high-performance high temperature infrared-transmitting AlON ceramics, we investigated the preparation and properties high-purity ultra fine AlON powders used for the solid-phase reaction method,and the AlON ceramics is prepared by hot pressed sintering.Firstly,γ-AlON powders were prepared by solid-state reaction processing with nano-γ-AlO3 and nano-AIN as starting materials.The effects of reaction temperature,holding time and γ-Al2O3/AIN ratio on the resultant phase compositions were investigated. It was found that the purity AlON powders could be synthesized when starting powders with 30mol% AlN were calcined at 1800℃ for 3h under N2 and the average particle size of the AlON powders is about 5μm.Further,by calculating the lattice parameter,we can get the formula Al17O21N3 of the synthetic γ-AlON from the lattice parameter corresponding to the composition of the crystal AlON relationship,Secondly,on the basis of the above experiment, we explored the preparation of γ-AlON powders by solid-state reaction processing with Al2O3 aerogels and nano-AIN.The results showed that,by analysis of Al2O3 aerogels,the method by solid-state reaction processing with Al2O3 aerogels and nano-AIN has theoretically confirmed great potential to synthetise high-purity ultra-fine high-activity AlON powders The purity AlON powders could be synthesized when starting powders with 30mol% AlN were calcined at 1800 for 4h under N2.Lastly,the purity γ-AlON powders which were prepared by solid-state reaction processing with nano-γ-Al2O3 and nano-AIN were calcined at 1800℃ for 3h in the air and milled for 2h.The effects of sintering temperature,pressure,holding time and sintering additives contents on the density,mechanical and optical properties of AlON ceramics were investigated.The result show that when adding the contents of 0.5wt% Y2O3 sintering additives,the ceramics were sintered at 30MPa pressure at 1800℃ for 3h.The measured relative density was 99.76%, the flexural strength was 231.53MPa,the elastic modulus was 146.89GPa.Sintering temperature at 30MPa pressure at 1900℃ for lh,when adding the contents of 0.5wt% Y2O3 sintering additives,the infrared transmittance of the AlON ceramics is only about 30%;without adding Y2O3 sintering additives under the same conditions,the infrared transmittance of the AlON ceramics is about 50%.