Positron trapping in functional spinel-type oxide ceramics.

Positron trapping is studied in functional spinel-type oxide MgAl2O4 and Cu0,4Co0,4Ni0,4Mn1.8O4 ceramics using positron annihilation lifetime spectroscopy. Obtained results are treated in terms of multi-exponential model of positron spectrum involving both positron trapping and ortho-positronium decaying. Crystallographical specifity of spinel structure reflects on the shortest lifetime component, while the middle component corresponds to the vacancy-like defects near boundaries. It is shown that in the cases of humidity-sensitive MgAl2O4 ceramics the positron trapping parameters in defects near grain boundaries occurs more efficiently in water-moistened ceramics.