Effects Of N/O And Atmosphere On The Transmittance Of Pressureless Sintered Transparent AlON Ceramics

Nitrogen alumina spinel??-AlON?is a kind of isotropic polycrystalline ceramic material,it is an important single phase of the AlN-Al₂O₃ phase diagram and has excellent optical performance and mechanical performance.Transparent AlON ceramics can be used as windshield of high-speed carrying tools or window materials working in high temperature,which has broad development prospects.In this paper,Al₂O₃ and activated carbon powders were used as the starting material to prepare AlON powder by carbothermal reduction method,the carbon content was changed to get different N/O of AlON powder,then the transparent AlON ceramics would be prepared separately in the atmosphere with or without carbon,the effects of N/O,sintering atmosphere and sintering process on optical performance of transparent AlON ceramic would be studied.The results show that:when carbon content are 5.0 wt%,5.6 wt%and 7.4 wt%,the AlON powders prepared by carbothermal reduction method are pure phase AlON,the N/O gets bigger and bigger as the carbon content increases.,the AlON powder contains Al₂O₃ when the carbon content is 4.4 wt%,and the AlON powder contains AlN when the carbon content is 8.6 wt%.In the atmosphere without carbon,the temperature of transparent AlON ceramic to get high densification quickly is 1800-1900 ?.When pressureless sintering in 1880 ?,the faster heating rate is beneficial to improve transparent AlON ceramic's relative density and transimittance;longer holding time can promote grain growth and get pure AlON,but the relative density and transimittance decrease as the holding time extended;when Y2O3 content is 0.1-0.5 wt%,the relative density and transimittance increase as Y2O3 content increase;when carbon content is 7.4 wt%,the relative density and transimittance of transparent AlON ceramic is biggest.In the atmosphere with carbon,under the condition that holding time is 150 minutes,the more appropriate temperature is 1850 ? to get transparent AlON ceramic with high transimittance,and the transparent AlON ceramic with the highest transimittance is prepared when the carbon content is 5.6 wt%,which is 80.2%;the holding time wan studied when the sintering temperature was 1880 ?,the results show that,the transimittance of transparent AlON ceramic increases as the holding time extends,the transimittance is 83.1%when the holding time is 480 minutes.When the AlON powders with higher N/O,whose carbon content is bigger,are pressureless sintered in the atmosphere with or without carbon,the grain size decrease as the N/O increase,it shows higher N content will restrain grain growth.Compared with sintering atmosphere without carbon,the atmosphere with carbon is more beneficial to obtain transparent AlON ceramic with high transimittance,the transimittance of ceramic is higher when the carbon content is 5.0-5.6 wt%?the N/O of AlON powder is 0.089-0.101?.