Characterisation of ceramic coatings sintering using residual stress measurements

Yttria stabilised zirconia (YSZ) containing a few per cent of aluminium was deposited on metal substrates by using electrophoretic deposition (EPD). After sintering at 1150–1300 °C, YSZ matrix coatings containing isolated Al2O3 particles were produced on metal substrates. The constraint applied by metal substrates affected the sintering of the coatings. To characterise sinterability of the YSZ/Al2O3 composite coatings, the residual stress applied to the Al2O3, termed as micro-stress here, has been measured using Cr3+ fluorescence spectroscopy after the removal of metal substrates. It was found that the residual stresses increased with the increase in sintering temperature and attrition milling time. The relation between the density of the coatings and the micro-stresses can be expressed by a simple analytical equation. In addition, residual stress measurements in the coatings with the addition of cordierite glass as sintering aid further proves that the residual stress can be used to show the degree of sintering. Therefore Cr3+ fluorescence spectroscopy is a very useful technique in characterising the sintering of the YSZ/Al2O3 composite coatings.