Aqueous sol–gel processing of precursors and synthesis of aluminum oxynitride powder therefrom

Abstract

For the first time, aluminum oxynitride (ALON) powders were synthesized using the precursors processed through aqueous sol–gel procedures. Appropriate quantities of aluminum nitride (AlN) powder and aqueous boehmite sol were mixed to obtain molecular stoichiometry of AlON. However, during the course of process, AlN powders reacted with the aqueous boehmite sol and disintegrated into its hydrated compounds. Such reactions altered the molecular stoichiometry between boehmite and AlN which was initially formulated for the eventual formation of AlON. Extensive investigations were carried out to analyse the behavior of AlN during the sol–gel processing. Hydrolysis of AlN in the aqueous sol–gel medium was circumvented by subjecting AlN to a surface modification process. The homogeneously dispersed boehmite sol and AlN mixture was further gelled, dried, and heat treated at temperatures between 1600 and 1850 °C for the formation of AlON powder. AlON phase formation was confirmed through XRD investigations, and its physical and microstructural properties were also evaluated through FESEM and TEM analyses. AlON powder with an average particle size of 490 nm was successfully synthesized in this study. This process is suitable for producing AlON powder in bulk quantities, and it can be used readily for further processes such as shaping and sintering to produce various optical products based on AlON.