Composite ceramic materials based on Si3N4and ZrO2stabilized by 3 mol% Y2O3have been formed using aluminum isopropoxide as a precursor for the Al2O3sintering aid. Densification was carred out by hot‐pressing at temperatures in the range 1650° to 1800°C, and the resulting micro‐structures were related to mechanical properties as well as to oxidation behavior at 1200°C. Densification at the higher temperatures resulted in a fibrous morphology of the Si3N4matrix with consequent high room‐temperature toughness and strength. Decomposition of the ZrO2grains below the oxidized surface during oxidation introduced radial stresses in the subscalar region, and from the oxidation experiments it is suggested that the ZrO2incorporated some N during densi