Diffusion of chromium in chrysoberyl

Abstract

Cr 3+ diffusion in chrysoberyl (BeAl 2O 4) irradiated by H + ions and electrons has been studied and compared with diffusion in non-irradiated samples. Chrysoberyl crystals were irradiated with 6 MeV H + ions to fluencies of 1×10 16 cm –2 for 25 min and with 10 MeV electrons to fluencies of 2×10 17 cm –2 for 1 h. Three different types of samples, which were doped with Cr 3+, were annealed in horizontal alumina tube furnaces by 50 K intervals in the temperature range from 1773 to 1923 K for 200 h. Scanning electron microscope–energy dispersive X-ray spectrometer (SEM–EDX) was used to measure the diffusion. Arrhenius equations for the diffusion coefficient for Cr 3+ in the temperature range 1773–1923 K were developed: Electron beam irradiated chrysoberyls, D cr=2.1×10 −5×exp (−482.3±18.2 kJ mol −1/ RT)m 2 s −1 Proton beam irradiated chrysoberyls, D cr=2.3×10 −3×exp (−545.4±25.0 kJ mol −1/ RT)m 2 s −1 Natural non-irradiated chrysoberyls D cr=2.2×10 −3×exp (−547.9±36.8 kJ mol −1/ RT)m 2 s −1 The results indicate that the chromium diffuses deepest into the electron beam irradiated chrysoberyls.