Sintered alumina samples with grain sizes of 1.7 or 4.5μm, in which Si impurities (90ppm) predominated, were investigated by means of positron annihilation lifetime spectroscopy at room temperature; using a new computer analysis method. A bulk lifetime of 122ps was detected. A trapped positron lifetime of 137ps, and a trapping coefficient above 6 x 1014/s, were attributed to defects within the grains. These traps were thought to be cationic vacancies, VAl”’, and clusters (nSiAl▪: VAl”’) which were produced by SiO2 dissolution into Al2O3. An annihilation process of small intensity and long lifetime was identified which might reflect annihilation in vacancy clusters located at the grain boundaries. The observed bulk lifetime was confirmed by measurements of high-purity Al2O3 single crystals.

Positron Lifetime Measurements in Sintered Alumina. G.Moya, J.Kansy, A.S.Ahmed, J.Liebault, F.Moya, D.Gœuriot: Physica Status Solidi A, 2003, 198[1], 215-23