Sintering of monodoped and mixtures of monodoped alpha alumina powders

The sintering of pure alumina is a delicate operation and often leads to a lack of densification or to a difficult to control abnormal grain growth. The addition of doping agents (MgO, TiO2, SiO2, ZrO2) has been widely covered in the literature with their role in the control of the microstructure. Their respective efficiency does not appear in the same stages of densification, it is thus possible to imagine that their action is complementary in the case of co-doping.In order to understand the effect of the codoping on the microstructural evolution and behaviour of α alumina during sintering, we chose to study three mixtures of pure industrial powders each one monodoped (Mg–Ti, Mg–Zr; Ti–Zr) obtained after milling and casting, and to compare them with each monodoped powder.The sintering of the pieces was followed by dilatometry and results are presented as the instantaneous densification rate as a function of relative density. This gives in situ information on the evolution of the microstructure.It is shown that the mixtures of monodoped powders always lead to a rate of densification less than that obtained by each monodoped powder and that the shape of the dilatometric curves can be largely influenced by one of the two doping agents.By using the model of the Master Sintering Curve (MSC), it is shown that, contrary to a monodoped powders, the sintering of mixtures of monodoped powders Mg–Ti and Ti–Zr does not present a single mechanism of diffusion under the imposed conditions of cycle.

In order to understand the effect of the codoping on the microstructural evolution and behaviour of alumina during sintering, we chose to study three mixtures of pure powders each one monodoped (Mg–Ti; Mg–Zr; Ti–Zr), and to compare them with each monodoped powder.The sintering of the pieces was followed by dilatometry and results are presented as the densification rate as a function of relative density.Figure optionsDownload as PowerPoint slide