Grain coarsening in gas pressure sintered silicon nitride

The grain growth of silicon nitride sintered by GPS has been studied in the case of an a-rich initial powder, As time increases, the microstructure becomes bimodal. A few large grains grow abnormally at the expense of the smallest ones. The growth rate of the major portion of grains is slow and can be assimilated to a normal growth with interface-reaction control. This rate limiting mechanism has been determined by three different methods: a method based on the Kingery' rate laws, a more direct method based on the variation of the grain size vs, the amount of the liquid phase and considerations on grain morphology according to Lee. (C) 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.