Structural stability of yttria doped zirconia membranes in acid and basic aqueous solutions

Hydrothermal corrosion behaviour of yttria doped zirconia (3Y–ZrO2) microfiltration membranes was investigated in aqueous solutions of acids and bases at room temperature and 80°C in a static corrosion test. Unsupported membranes of 3Y–ZrO2 prepared by slip casting had 100% tetragonal structure after sintering at 1200°C. Weight loss, phase composition, porosity, pore size and surface area as well as residual stress of the samples was measured after corrosion test. A weight loss was detected in all cases and it was higher at 80°C. There was no direct correlation between weight loss and the amount of monoclinic phase transformed from tetragonal phase. The results showed that in these solutions phase transformation of 3Y–ZrO2 membrane occurred even at room temperature which is lower than the minimum range of temperature that has been reported for dense counterparts. However, the amount of monoclinic phase after corrosion was not more than 13% in the samples. Microcracks were not found in the samples with the highest amount of monoclinic phase after the corrosion test. Although phase transformation was found even at room temperature but the lack of microcracks prohibited the autocatalytic propagation of the phase transformation from the pore surface into the structure. 3Y–ZrO2 membrane showed a good structural stability in these corrosive solutions despite having porous structure.