Thermoluminescence and sintering of high-purity α-alumina doped by Zr, Th and Ca

Two parameters were studied upon the thermoluminescence (TL) properties and the sintering behaviour of α-alumina: the atmosphere during the heat treatment used to transform γ-Al2O3 into α-Al2O3 and the doping by Zr and Th. It appears that a reducing atmosphere tends to delay the sintering compared with the oxidising atmosphere until 1600°C. Above this temperature, the shrinkage starts again, which is attributed to a change in the mechanism of sintering of α-Al2O3. The concentration of point defects created through charge compensation as the tetravalent dopant integrates into the host material increases until the solubility's limit of the dopant in alumina is reached. Above this concentration, the peaks on the TL glow curves stabilize, and the specific area of the powders stabilizes at its higher value. As a consequence, the final densities obtained for α-Al2O3:Th and α-Al2O3:Zr are the best when the solubility's limit of the dopant in alumina is reached.