Doped alpha-alumina powders have been synthesised by thermal treatment of gamma-alumina under a controlled atmosphere. Two TL peaks, located at 200°C and 365°C, have been detected in almost all samples. Their intensity is strongly dependent on the atmosphere and on the nature of introduced dopants. The influence oh these parameters on point defects concentrations is analused, and compared with TL intensity variations. It is suggested that aluminium vacancies are the trap defects responsible for these two peaks and, depending on the preparation conditions, F centres or Cr3+ can be the recombination centres. Two powders have been selected for dosimetry use. Their sensitivity to X ray radiation have been compared with that of Al2O3 : C powder (TLD-800). The TLD-800 dosimetric peak corresponds exactly to their 200°C peak.