Aluminum Oxynitride (ALON) Spinel

Abstract

Publisher Summary This chapter describes aluminum oxynitride (ALON) as a crystal made of various amounts of aluminum oxide and aluminum nitride, with the aluminum–nitride content between 27 and 40 mole percent. The resulting material—a nitrogen-stabilized cubic aluminum oxide—is face-centered cubic with spinel structure. ALON is termed a nonstoichiometric spinel because some cation sites are occupied by vacancies. It can be produced by a variety of methods, including reaction sintering of alumina and aluminum nitride, simultaneous reduction and nitridation of alumina, combustion-like reaction of aluminum metal with oxygen and nitrogen, and reaction of gases. Commercial optical ALON is made by reacting the raw materials, pressing them into a near-finished shape, and firing at a high temperature to produce a fully dense, transparent ceramic. The resulting high-temperature, high-strength ceramic is used for windows and optical elements where hardness and resistance to harsh environments is important. This chapter provides an overview of the optical elements of ALON and reviews property data for this material given in the literature. The chapter also presents transverse and longitudinal optical frequencies of ALON as determined by reflectance measurements. The transverse optical frequencies are the mode locations, and the maximum longitudinal frequency is an important parameter in the multiphonon model as it designates the maximum phonon frequency.