Pressureless Sintering Highly Transparent AlON Ceramics By Using Ba²⁺/ca²⁺as Additive

AlON is an important kind of oxide polycrystalline transparent ceramic material which has an excellent transmittance in both ultraviolet and infrared wavelengths.It also has mechanical properties,excellent high temperature and corrosion resistance that can be applied to many fields such as transparent armor,infrared window materials,optical instruments and so on.In general,AlON has a broad application prospect.This paper uses AlON powder as the raw material.The AlON powder is prepared by carbothermal reduction method and it is added in BaCO3 or CaCO3 as its sintering additives.The influence of sintering aid on the phase composition,microstructure,mechanical properties,especially optical properties of AlON transparent ceramics is studied in the experiment with BaCO3 or CaCO3 sintering aid and different preparation processes and sintering processes respectively.At the same time,the sintering process is adjusted to obtain the AlON transparent ceramics which meet the expected benefit with the lowest economic cost.When BaCO3 is used as a sintering aid with ball milling of 24h,the AlON transparent ceramic with an optical transmittance of 75.89%can be obtained with the BaCO3 content of 0.4%.When the ball milling time reaches 48h and the content of BaCO3 is 0.2%,the AlON transparent ceramic with optical transmittance of 80%can be obtained.Prolonging the ball milling time is beneficial to get higher light transmittance AlON ceramics in lower content.When the content of CaCO3 is 0.2%to 0.4%,the AlON transparent ceramics' can get high optical transmittance.When the ball milling time is 24h and the content of CaCO3 is 0.4%,the optical transmittance of AlON ceramics which can get 82.61%are the best.In order to reduce the economic cost and ensure that the sintering temperature is constant at 1870 degrees,the maximum optical transmittance of AlON transparent ceramics increases by about 5%when the holding time increases by 60min.When the holding time 150min is constant,the maximum optical transmittance of AlON transparent ceramics is increased by about 10%at a sintering temperature range of 30 degrees.