INFLUENCE OF THE CALCINING CONDITIONS ON THE THERMOLUMINESCENCE OF PURE AND DOPED ALPHA-ALUMINA POWDERS

Pure alpha-Al2O3 powders have been prepared by thermal decomposition o f ammonium alum (NH4Al(SO4)(2).12H(2)O). The calcinations were perform ed at different temperatures, and under flowing oxygen or nitrogen or hydrogenated argon. The thermoluminescence of these powders after X ra y irradiation at room temperature is studied from room temperature to 780 K. Four peaks are found in almost all samples at 335, 420, 470 and 635 K. Only the intensities are variable. The last two peaks are spec ifically interesting: the 470 K peak intensity is slightly higher for a reducing atmosphere whereas the 635 K peak intensity increases signi ficantly for an oxidising atmosphere. This high temperature peak could be very convenient for dosimetry applications. Thermoluminescence aft er X irradiation at low temperature (80 K) and thermostimulated exoele ctronic emission results are also reported. Using the same procedure, alumina powders doped with Mg2+, Cr3+ and Th4+ were also studied.