Pressureless sintering of aluminium nitride: effect of concentration of additives and sintering conditions on properties

Abstract

Pressureless sintering, in the presence of additives such as Y 2O 3, CaO and a mixture of CaO and Y 2O 3, of commercial aluminium nitride (AIN) powders made by carbonitridation of aluminium oxide and direct nitridation of aluminium metal has been studied. The influence of concentration of the additives, and the sintering temperature and duration on such properties of the sintered shapes as density, thermal diffusivity and conductivity and electrical resistivity has been investigated. In addition, optical-, scanning- and transmission-electron-microscopy-based characterization of sintered bodies has been carried out to interpret the relationship between microstructure and thermal diffusivity. The study indicates that, for the pressureless sintering of AIN with the realization of high thermal diffusivity for the sintered bodies as the major objective, Y 2O 3 is superior to CaO as a sintering aid. Another important finding is that a higher sintering temperature at a fixed sintering duration and an increased sintering duration at a fixed sintering temperature will both result in a considerably enhanced thermal diffusivity for pressureless-sintered AIN bodies.