Origin of a shrinkage anomaly in anatase

In our present study, a shrinkage anomaly present during sintering in an anatase powder compact was examined. It was observed that the shrinkage stagnates during sintering. This anomaly has been investigated using dilatometry, X-ray powder diffraction, and scanning electron microscopy. Quantitative phase analysis using X-ray diffraction revealed that the shrinkage anomaly is correlated to the phase transition from anatase to rutile. A calculation based on specific volumes of anatase and rutile showed that the phase transition generated 8.6% additional porosity in the anatase powder compact and this retards the densification as well as the shrinkage in the anatase sample. Microstructural observation of anatase and rutile samples having the same shrinkage confirmed this result.