QUANTITATIVE KINETIC-ANALYSIS OF SILICON NITRIDATION

Kinetic analysis of silicon nitridation requires intrinsic single-part icle behaviour to be isolated from global or compact effects that typi cally manifest during the reaction-bonding process. These effects aris e from the influence of adjacent particles, which modify the macropore structure as the reaction proceeds. Much of the variation in the publ ished kinetic data can be attributed to compact effects, particle shap e, and size distribution, resulting in a myriad of models being report ed, each only applicable to the nitridation conditions in which the da ta were obtained. Our work clearly demonstrates that the intrinsic sin gle-particle nitridation behaviour is well described by a sharp-interf ace model, with diffusion control (E(a) = 301.5-31 0.0 kJ mol-1) throu gh an expanding Si3N4 product layer developing on the individual grain s. For the nitridation of silicon compacts, the reaction-bonding proce ss can be divided into three fundamental stages- (1) initial devitrifi cation/nucleation, (2) massive nitridation, and (3) termination by fur ther sintering, densification, and coarsening of the Si3N4 product. Fa ctors influencing and controlling each stage are summarized.