Pure Al2O3 powders have been prepared by thermal decomposition of ammonium alum (NH4Al(SO4)2. 12H2O). The calcinations were performed at different temperatures, and under flowing oxygen or nitrogen or hydrogenated argon. The thermoluminescence of these powders after X ray 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 specifically interesting : the 470 K peak intensity is slightly higher for a reducing atmosphere whereas the 635 K peak intensity increases significantly for an oxidising atmosphere. This high temperature peak could be very convenient for dosimetry applications. Thermoluminescence after X irradiation at low temperature (80 K) and thermostimulated exoelectronic emission results are also reported. Using the same procedure, alumina powders doped with Mg2+, Cr3+ and Th4+ were also studied.