Comparison of the early stage of low-temperature degradation in ZrO$_2$(Y$_2$O$_3$) and ZrO$_2$(MgO) ceramics

Samples of yttria-stabilized zirconia (YSZ) and magnesia-stabilized zirconia (MSZ) ceramics were analyzed by grazing angle XRD technique in order to gain insights into the effects of the autoclave treatment (140$^\circ$, 207 kPa, 15 h) on transformation of tetragonal ZrO$_2$ into monoclinic zirconia (known as low-temperature degradation, LTD). Models were developed to describe the distribution of $m$-ZrO$_2$ across the depth of the degraded layer. Based on the results of the study it was established that the $m$-ZrO$_2$ contents in the polished YSZ surfaces after the autoclave treatment was changed by 48%, whereas those of MSZ–only by 4%. Moreover, the hydrothermal modification process is confined to the thin near-surface layer. This layer had thickness corresponding approximately to one average grain size. It was shown that the grazing angle XRD technique was the only method capable of adequate characterization of the degraded layer thickness and overall LTD effect parameters.