Aluminium titanate formation by solid state reaction of AI2O3 and TiO2 single crystals

Abstract

Al2O3 and TiO2 reaction couples have been prepared from polished prisms of sapphire and rutile single crystals with bothc axes normal to the common interface. The microstructures were analysed after heat treatments in oxygen at 1690 and 1780 K respectively, sometimes with a superimposed 20 K temperature difference across the rutile. A polycrystalline reaction layer develops via a complex nucleation and growth mechanism after an apparent incubation time during which the TiO2 crystals saturate themselves with aluminium by AI2O3 dissolution and solid state transport. A quantitative evaluation of the growth kinetics also provides selfconsistent estimates of effective diffusivities along the TiO2 c axis and across the titanate layer, respectively.