PAL spectroscopy in application to humidity-sensitive MgAl2O4 ceramics

It is shown that positron annihilation technique invariant of lifetime spectroscopy is a quite promising tool for nanostructural characterisation of extended free-volume defects in humidity-sensitive spinel-type alumomagnesium MgAl2O4 ceramics, the best results being achieved provided three-component fitting procedure with arbitrary lifetimes is applied to treat mathematically the measured spectra. Main channels of positron annihilation in the investigated ceramics are supposed to be connected with individual vacancies and vacancy-like clusters, powder particle surfaces, large-angle grain-boundaries and tiny nanostructured voids (pores) with average radius near 3.0 angstrom, which can capture positronium atoms. The developed approach seems to be especially attractive in tight combination with other experimental structural probes, first of all conventional mercury porosimetry and small-angle X-ray scattering technique. (c) 2005 Elsevier Ltd. All rights reserved.