Transformation of Positron Trapping Parameters Caused by Water Molecules in Voids Near Grain Boundaries in MgAl2O4 Ceramics

Changes of positron trapping parameters and modes caused by adsorption and desorption processes in MgAl ₂ O ₄ ceramics sintered at 1400 °C for 2 h are studied. It is shown that so-called catalytic effects are represented by the positron trapping rate in defects localised near grain boundaries in ceramics, which is calculated on the assumption that the positrons lifetimes of the first and the second components remain unchanged. The processes of adsorption-desorption of water in MgAl ₂ O ₄ ceramics are fully described by observed changes in this parameter.