Titanium effect on phase transformation and sintering behavior of transition alumina

The sintering behavior of doped γ-alumina powders studied by dilatometry and electron microscopy is analysed with a particular emphasis on the role of titanium on the various densification steps. Compared with other doping elements, such as Mg, Y and Zr, which do not improve α-phase densification, titanium enhances this densification step by a fast decrease of internal colony porosity. This internal densification of single crystalline zones is attributed to the lengthening of the elementary bricks in titanium-doped samples. A transient increase in densification rate is also observed, corresponding to the precipitation when during grain growth, grain boundaries become saturated with titanium. Final densities close to the theoretical values are obtained.