Nitride & Oxy-Nitride Ceramics for High Temperature and Engineering Applications

Abstract

Nitrides and oxynitrides of silicon and aluminum occupy prominent positions among other non-oxide members of ceramics on account of their inherent unique combination of properties arising out of their directional covalent bonding in the condensed state. Since many reviews could be found in the literature on the materials either individually or combining some of them, the present article is devoted to the key areas of the present research on the developments of these materials. For example, α’ – SiAlON is now attracting significant attention and the article highlights how compositional variations could lead to easy densification and improvement of its mechanical properties. Experimental results from various authors show that the mechanism of stabilization of α’ – SiAlON is very complex and cannot be explained on the basis of the size of the metal cations and solubility in the transient glassy phase. Y, Yb, Dy and to some extent Ca are good for stabilization of the phase. Evolution of different phases during temperature rise and how these phases affect sintering of the α’ material has been presented in this article. In-situ formation of elongated β’ grains have been shown to increase the toughness of the material. Simultaneously, the development of AlN ceramics in regard to application of this ceramic in different areas apart from that of microelectronics has been discussed. +Improved mechanical and electrical properties of AlN and its composites have shown their promise in diverse applications such as armors, electron tube components and dielectric devices.