Preparation of Thin Mullite Films

Abstract

Aluminosilicate glass films having compositions approximately that of mullite produced by reactive sputtering of aluminum‐silicon alloys are discussed. Data are given on the speed of deposition under certain conditions for a variety of metal and ceramic substrates. Mullite crystals with the needle habit are formed from the initial amorphous film by subsequent heat treatment of about 1 hour at temperatures of 1100° to 1400°C. The number and size of the crystals are affected by firing conditions, composition, and thickness of the film and by nucleating agents such as carbon on the surface of the film as indicated by transmission electron micrographs of unsupported films. The reaction of the oxide films with some supporting ceramic substrates has also been studied.