Densification behaviour of Ca-α-sialons

In this paper three methods of densification of Ca-α-sialon are compared. It is shown that both reaction hot pressing and reaction sintering are convenient methods to obtain densities close to theoretical values. For the densification of carbothermally prepared Ca-α-sialon powders the influence of the amount of CaO as a sintering additive has been shown to be significant. The highest density was reached with 15 wt.% CaO (∼ 97% relative density). The ‘mechanisms’ of sintering using the three mentioned methods (reaction hot pressing, reaction sintering and sintering Ca-α-sialon powder with CaO as a sintering additive) appear to be similar. First a rearrangement of the particles takes place due to the presence of a liquid phase, followed by a solution/precipitation mechanism. The mechanism for liquid phase sintering of Ca-α-sialon is similar to that described in literature for other Ln-α-sialon (Ln=Y, lanthanideʹs) materials.