Redox behavior during the transformation in zirconia with low yttria content

Martensite-like phase transformation in zirconia doped with low yttria content, which progresses by either athermal or isothermal routes from tetragonal to monoclinic has been investigated in terms of the redox behavior. Thermo-gravimetric (TG) analyses in air and reducing environments were carried out. It was revealed that, during cooling in air, oxidation started from the Ms (martensitic transformation start temperature) and was gradually saturated to room temperature. However, differential thermal analysis (DTA) showed that the transformation takes place within a temperature span of 25 °C. This means the transformation triggers the oxidation reaction, but oxidation itself is dominated by a diffusion process, independently to the transformation phenomenon. Therefore it was concluded that, in the oxidizing environment, oxygen diffusion is not essential to the transformation but incidental to the phenomenon.