Diffusion of chromium in sapphire: The effects of electron beam irradiation

In this paper, we measured the diffusion of chromium in sapphire (α-Al2O3). Sapphires were irradiated with 10 MeV electrons to fluencies of 2×1017 cm−2 for 1 h. Annealing experiments were performed using the three sapphire samples prepared using the three different diffusion methods at temperatures ranging from 1773 to 1923 K for 200 h under an oxidation condition of 1 atm. The diffusion of chromium in sapphire was profiled using scanning electron microscope-energy dispersive X-ray spectrometry (SEM-EDX). The following Arrhenius equations for the diffusion coefficient of Cr3+ were obtained over the temperature range of 1773–1923 K:Coated and electron beam-irradiated sapphire samples,Dcr=1.8×10−7exp(−385.7±18.2kJmol−1/RT)m2s−1;Electron beam-irradiated sapphire samples,Dcr=3.3×10−7exp(−401.0±14.7kJmol−1/RT)m2s−1;Natural non-irradiated sapphires,Dcr=2.8×10−7exp(−405.9±28.7kJmol−1/RT)m2s−1These results indicate that chromium penetrated deepest within the coated and electron beam-irradiated sapphire samples.