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

Two parameters were studied upon the thermoluminescence (TL) properties and the sintering behaviour of a-alumina: the atmosphere during the heat treat ment used to transform gamma -Al2O3 into alpha -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 degreesC. Above this temp erature, the shrinkage starts again, which is attributed to a change in the mechanism of sintering of alpha -Al2O3. The concentration of point defects created through charge compensation as the tetravalent dopant integrates i nto 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 c urves stabilize, and the specific area of the powders stabilizes at its hig her value. As a consequence, the final densities obtained for alpha -Al2O3: Th and alpha -Al2O3:Zr are the best when the solubility's limit of the dopa nt in alumina is reached. (C) 2001 Elsevier Science B.V. All rights reserve d.