Crystals of C-doped -phase material were studied using luminescence, optically stimulated luminescence, photo-transferred thermoluminescence and X-ray luminescence techniques. The results were compared with those which were obtained for nominally pure samples. It was found that the main thermoluminescence and photo-transferred thermoluminescence peaks appeared at the same temperatures in C-doped samples. They also had the same thermal activation energies as those in the pure material; thus indicating that they were due to the same traps. However, some marked differences were observed in the emission spectra of C-doped and pure samples. The thermoluminescence emissions of the 260K peak in the C-doped crystals exhibited principal bands at 310 and 330nm; with weaker bands at 410, and near to 520nm. At 280K, and higher temperatures, the 330 and 410nm bands became stronger. The 330 and 410nm bands also appeared in the photo-transferred thermoluminescence, optically stimulated luminescence and X-ray luminescence emission spectra of the doped samples. In the case of pure crystals, only a 310nm band was recorded at low temperatures. At temperatures above 280K, a weak broad band appeared near to 325nm. This band could be resolved into 2 components, at 310 and 330nm, which were attributed to 2 different processes. The 330 and 410nm bands were attributed to F+ and F-center emissions, respectively. This assumption was supported by measurements of the excitation spectra of the 330 and 410nm optically stimulated luminescence emission bands, which exhibited maxima at wavelengths that coincided with the F+ and F absorption bands. The present results were also consistent with previous conclusions concerning the relatively high F+ concentration in C-doped -phase alumina crystals. An emission near to 520nm had previously been attributed to an interstitial Ali+ ion. The 310nm band, which appeared in the same situations as the weaker 520nm band, was also suggested to be due to an interstitial Ali+ ion.

A.Shmilevich, R.Chen, D.Weiss, N.Kristianpoller: Materials Science Forum, 1997, 239-241, 65-8