Phase transformations in face centered cubic (Al 0.32Cr 0.68) 2O 3 thin films

Abstract

Face centered cubic (Al 0.32Cr 0.68) 2O 3 thin films have been annealed in the temperature range of 500-1000°C during 2-8h. The fcc structure of the film remains intact when annealed at temperatures up to 700°C for 8h. X-ray diffraction and transmission electron microscopy show the onset of phase transformation to corundum phase alloys in the sample annealed at 900°C for 2h, where annealing at 1000°C for 2h results in complete phase transformation to α-(Al 0.32Cr 0.68) 2O 3. In-plane and out-of-plane line scans performed in EDX TEM and θ/2θ XRD patterns did not show any phase separation into α-Cr 2O 3 and Al 2O 3 prior and after the annealing. The apparent activation energy of this process is 380-480kJ/mol as determined by the Johnson-Mehl-Avrami model. © 2012 Elsevier B.V.