Thermal stability of Ti3SiC2 thin films

The thermal stability of Ti3SiC2(0001) thin films is studied by in situ X-ray diffraction analysis during vacuum furnace annealing in combination with X-ray photoelectron spectroscopy, transmission electron microscopy and scanning transmission electron microscopy with energy dispersive X-ray analysis. The films are found to be stable during annealing at temperatures up to similar to 1000 degrees C for 25 h. Annealing at 1100-1200 degrees C results in the rapid decomposition of Ti3SiC2 by Si out-diffusion along the basal planes via domain boundaries to the free surface with subsequent evaporation. As a consequence, the material shrinks by the relaxation of the Ti3C2 slabs and, it is proposed, by an in-diffusion of 0 into the empty Si-mirror planes. The phase transformation process is followed by the detwinning of the as-relaxed Ti3C2 slabs into (111)-oriented TiC0.67 layers, which begin recrystallizing at 1300 degrees C. Ab initio calculations are provided supporting the presented decomposition mechanisms. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.