Exploring nanovoids in spinel ceramics using positron–positronium trapping model.

The investigation focused on nanovoids (free-volume defects) in spinel MgAl2O4 ceramics, synthesized at various temperatures, both before and after saturation (water-immersion), utilizing the positron annihilation spectroscopy method. The findings were analyzed within the framework of a multi-channel model. It was demonstrated that this model integrates channels capturing positrons by volumetric defects and the decay of ortho-positronium atoms. Within this refined approach, the first component reflects the microstructural characteristics of the spinel structure, the second component corresponds to volumetric defects near grain boundaries, while the third pertains to the "pick-off" process of ortho-positronium annihilation within water-filled nanopores of the ceramics. [ABSTRACT FROM AUTHOR]