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2 Archives of Materials Science

2 2006

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Positron trapping in functional spinel-type oxide ceramics.

Klym H., Balitska V., Shpotyuk O. I., Ingram A.

Archives of Materials Science

2006

Vol. 27, nr 4

177-187

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.

Positron trapping in chalcogenide glasses: a comparison between arsenic sulphide and selenide.

Shpotyuk O. I., Filipecki J., Kozdras A., Popescu M., Hyla M.

Archives of Materials Science

2006

Vol. 27, nr 4

167-175

Positron annihilation lifetime measurements are performed for stoichiometric arsenic suphide. It is shown that two-state positron trapping model is valid for this glass as it has been shown previously for stoichiometric arsenic selenide. Two-component fitting parameters of LT computer program, describing positron annihilation in glassy As2S3, are close to those of glassy As2Se3. They are in good agreement with theoretically calculated distribution of nanovoid radii in these materials.