Formation of mullite thin film via a sol-gel process with polyvinylpyrrolidone additive

Several tasks were tried to prepare crack-free mullite films on silica subs trates. Basically, a sol containing TEOS (Tetraethylorthosilicate) and boeh mite colloid was used for spin coating on silica substrate. The formulation of the sols was kept in stoichiometric composition 3Al(2)O(3)(.)2SiO(2), o r contained a crack-limiting agent, Polyvinylpyrrolidone (PVP). These films were then treated up to 1300 degreesC. The properties of the sols and the dried films were characterized by rheometer. various thermal analysis techn iques (DTA, TGA and TMA). also by XRD, SEM and TEM. The mullite film shows randomly oriented grains in sizes from 0.1 mum to a few micrometers. The fi lms still contain fine theta- and delta -Al2O3 particles after being treate d at 1280 degreesC for 1 h. (C) 2001 Elsevier Science Ltd. Ail rights reser ved.