* Astronomy

Title: Positron Annihilation Lifetime Spectroscopy in the analysis of microstructural changes of Y-TZP ceramics
Author: P. Parente, G. Ferro, A. Tucci, L. Esposito, G. Timellini

Positron Annihilation Lifetime Spectroscopy (PALS) technique was used for microstructural characterisation of Y-TZP ceramics. Spectroscopic measurements were carried out on ceramic surfaces subjected to tribological tests. Positron annihilation mean lifetime values, measured both on the unworn and worn surfaces, showed a different behaviour when different sliding velocities were used. For samples tested at 0.3 and 0.7 m/s, the decrease of values of positron mean lifetime measured on the worn surfaces, compared with the measurements of the unworn surfaces, was related to the increased positron trapping in the grain-boundary-related space-charge region, due to defect equilibrium changes with grain size reduction. For samples tested at 1.0 m/s, the higher mean lifetime values, found on the worn surfaces, was ascribed to the increase in zirconia monoclinic phase fraction present on the worn scars.

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