Effects of Y2O3 and ZrO2 on the densification of Si3N4-Zr(Y)O2 composites

The effects of ZrO2 and Y2O3 on the densification of hot-pressed Si3N4-Zr(Y)O2 composites have been studied. High density could not be obtained by the addition of pure or 3-mol%-Y2O3-doped ZrO2 in this composite; however, nearly full density (>97%) could be obtained in Si3N4 using 6- and 8-mol%-Y2O3-doped ZrO2. It is concluded that Y2O3 diffusing out from the added Zr(Y)O2 promoted the densification and that ZrO2 also had some role in the formation of an oxynitride glass.