Influence of La Doping on the Apparent Activation Energy of α-Al<sub>2</sub>O<sub>3</sub> during the Densification Process at Constant Heating-Rate

Abstract

The apparent activation energy for densification is a characteristic quantity that elucidates the fundamental diffusion mechanisms during the sintering process. Based on the Arrhenius theory, the activation energy for densification of the pure and La doped α-Al2O3at constant heating-rates sintering has been estimated. Sintering of α-Al2O3and La doped powder has been executed by the way of a push rod type dilatometer. It was shown that the shrinkage and the relative density of the samples decreased with increasing heating rates. At the same sintering condition, the shrinkage of the pure α-Al2O3was higher than that of the La doped. According to the calculation, it was found that the apparent activation energy had a single value and did not depend on the relative density for both samples. The apparent activation energy of the pure α-Al2O3was 374.3kJ/mol, which was lower than that of La doped (966.5kJ/mol). So the densification process for α-Al2O3was retarded due to La doping, which was consistent with experimental results of the shrinkage.