Atomic-deficient nanostructurization in water-sorption alumomagnesium spinel ceramics MgAl2O4

Abstract

Atomic-deficient nanostructurization in alumomagnesium MgAl2O4 ceramics sintered at 1100–1400 °C caused by water sorption are studied employing positron annihilation lifetime spectroscopy. Detected PAL spectra are reconstructed from unconstrained x4-term decomposition, and further transformed to x3-term form to be applicable for analysis with x3–x2-CDA (coupling decomposition algorithm). It is proved that water-immersion processes reduce positronium (Ps) decaying in large-size holes of ceramics (1.70–1.84 nm in radius) at the expense of enhanced trapping in tiny (~ 0.2 nm in radius) Ps-traps. The water sorption is shown to be more pronounced in structurally imperfect ceramics sintered at Ts = 1100–1200 °C due to irreversible transformations between constituting phases, while reversible physical-sorption processes are dominated in structurally uniform ceramics composed of main spinel phase.