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

Abstract

In this paper, we measured the diffusion of chromium in sapphire (alpha-Al(2)O(3)). Sapphires were irradiated with 10 MeV electrons to fluencies of 2 x 10(17) 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 Cr(3+) were obtained over the temperature range of 1773-1923 K:Coated and electron beam-irradiated sapphire samples,D(cr) = 1.8 x 10(-7) exp(-385.7 +/- 18.2 kJ mol(-1)/RT)m(2)s(-1);Electron beam-irradiated sapphire samples,D(cr) = 3.3 x 10(-7) exp(-401.0 +/- 14.7 kJ moL(-1)/RT)m(2)s(-1);Natural non-irradiated sapphires,D(cr) = 2.8 x 10(-7) exp(-405.9 +/- 28.7 kJ mol(-1)/RT)m(2)s(-1)These results indicate that chromium penetrated deepest within the coated and electron beam-irradiated sapphire samples.