Effect of N2 sintering atmosphere on the hardness of sol–gel films of 3 mol% Y2O3-stabilized ZrO2

A one-pot approach to hardening ZrO2-based films prepared by the sol–gel method is presented. It entails performing the sintering in a nitrogen atmosphere, instead of in the conventional air atmosphere. It is shown that, when the sintering temperature is high enough, gas nitriding takes place in the ceramic film, leading to a 15% increase in its hardness. This occurs because more nitrogen solutes are incorporated into the crystal lattice of the 3YSZ host, forming solid solutions (i.e., greater solid–solution-effect hardening). The proposed gas nitriding is simple and cost-effective, and adds no additional steps to the processing routine. This suggests that it may have an important role to play in the fabrication of hard ceramic films from liquid precursors.