Sintering of an ultra pure a-alumina powder: I. Densification, grain growth and sintering path

Sintering in air of an ultra pure a-alumina powder has been investigated. Isothermal experiments have been conducted on green samples shaped by slip casting. The grain growth and densification kinetics have been established. The ‘‘relative density/grain size’’ trajectory, called ‘‘sintering path’’, has been drawn. Hypotheses concerning the mechanisms controlling grain growth and densification have been formulated. For the first time, it is shown that grain growth and densification kinetics exhibit two distinct regimes, where an initial point defect formation step plays a key role. When point defects have been generated, the diffusion of the associated Al3+ cations controls grain growth and densification.