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Surface Concentration of Defects at Grain Boundaries in Sintered Alumina Determined by Positron Annihilation Lifetime Spectroscopy

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Kansy J., Si Ahmed A., Liebault J., Moya G.

Acta Physica Polonica A

2001

vol. 100

issue 5

737-742

Sintered alumina samples of grain diameters spanning from 1.2 to 4.5μm have been investigated by positron annihilation lifetime spectroscopy. One series of samples was produced from material containing about 150 ppm impurities (mainly SiO_2). The second one was made from material having about 2700 ppm of various elements (SiO_2, MgO, CaO). Two models of positron trapping at grain boundaries are compared: The first one relates to the diffusion-limited regime; and the other one - to the transition-limited regime of trapping. As a result the relative change of surface concentration of defects at grain boundaries is determined. Additionally, the positron diffusion constant in bulk alumina at room temperature, D_+=0.36±10 cm^2/s, is estimated.

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1 Acta Physica Polonica A

1 2001

1 Kansy J.

1 Liebault J.

1 Moya G.

1 Si Ahmed A.

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Surface Concentration of Defects at Grain Boundaries in Sintered Alumina Determined by Positron Annihilation Lifetime Spectroscopy