Abstract
AbstractPositron annihilation lifetime spectroscopy (PALS) measurements were performed to study the influence of the sintering temperature, heating rate and dwell time on the porosity and on the defect concentration on series of spark plasma sintered alumina samples. Two long‐lived components were found in the PALS spectra and were associated to pick‐off annihilation of ortho‐positronium localized in two types of pores. The same spectra were analysed in the frame of the three‐state‐trapping model and information for the intragranular and at grain boundary defect concentration was extracted. At sintering temperatures below 1200 °C the regime of the high (600 °C/min) heating rate leaded to more efficient defect annealing compared to the regime of the low (8 °C/min) heating rate, while at higher temperatures this difference disappeared. The low heating rate at high temperatures leaded to more compact samples compared to these sintered at the high heating rate as a result of intergranular pore concentration decrease.
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