Positron Annihilation Lifetime Tools for Nanostructural Study of Spinel Ceramics

Positron annihilation lifetime spectroscopy was used for studied nanostructured MgAl<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> spinel-type ceramics. The study has expanded the multi-channel positron annihilation model to encompass MgAl<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> spinel. This model effectively integrates positron trapping through both volume defects and the decay of ortho-positronium atoms. Within this refined framework, the first component of positron lifetimes reflects the specific microstructural characteristics of the spinel structure. The second component corresponds to volume defects located near grain boundaries, while the third component addresses the “pick-off” annihilation process of ortho-positronium within moisture-filled nanopores embedded in the ceramic. This investigation highlights the significant influence of moisture absorption processes on positron trapping by defects in nanostructured $\mathbf{M g A l}_{2} \mathrm{O}_{4}$ ceramics.