Spinel Sialons We gratefully acknowledge the synthesis of β-sialon starting material by M. Zenotchkine and the fruitful conversation with James W. McCauley concerning the existence of γ-Al3O3N. The department of high-pressure/mineral physics, Max-Planck-Institut für Chemie, Mainz, is acknowledged for providing technical support. We are further grateful for the financial support of this work provided by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. E.K. thanks the Alexander von Humboldt Foundation for granting a Lynen fellowship.

Abstract

Excellent mechanical properties make γ-Si2AlON3, one of the first spinel sialons and 4-3-spinels, a promising material for structural and abrasive applications. The hardness of this phase synthesized at 13 GPa/1800°C surpasses that of the low-pressure α- and β-sialons, which are used for metal-cutting and engineering applications. The picture shows a γ-Si2AlON3 surface that was used for Vickers hardness testing and indicates the structural relation between β- and γ-sialons and the corresponding phases of Si3N4.