Exploring nanovoids in spinel ceramics using positron–positronium trapping model

Abstract

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.

Keywords:

• ceramics
• free-volume
• humidity
• nanovoids
• positron annihilation
• sensors

Acknowledgments

Authors thank to the Ministry of Education and Science of Ukraine for the support. H.K. thanks to Prof. O. Shpotyuk for discussion of results and A. Ingram for assistance in PAL experiments.

Disclosure statement

No potential conflict of interest was reported by the author(s).