Effects of electron-beam irradiation, a thin-Ti layer, and a BeO additive on the diffusion of titanium in synthetic sapphire

Titanium was allowed to diffuse into synthetic sapphire (α-Al2O3) at 1773–1923 K for 200 h in air. Specimens were prepared by four different methods. Samples were irradiated with a 10 MeV electron beam to fluencies of 2×1017 cm−2 for 1 h to induce vacancy formation. A 1-μm layer of titanium was sputtered onto sapphire samples to provide intimate contact with the diffusing elements. Ti diffusion was performed using TiO2 powder or a mixture of TiO2 and BeO powders in a ratio of 95:5 to take advantage of the beryllium activity. Ti diffusion was profiled using scanning electron microscope-energy dispersive X-ray spectrometry (SEM–EDX). The diffusion coefficients of Ti were as follows: Sapphire irradiated, coated with Ti, and embedded in TiO2/BeO mixture. image Sapphire irradiated, coated with Ti, and embedded in TiO2 powder. image Sapphire irradiated, non-coated and, embedded in TiO2 powder. image Sapphire non-irradiated, non-coated, and embedded in TiO2 powder. image These results demonstrate that titanium penetrated the deepest into the sapphire samples that were electron-beam-irradiated, coated with Ti, and embedded in the TiO2/BeO mixture.