Results of the comprehensive morphological study of CdI2–BiI3 layered crystals are presented. Direct AFM observations of micro- and nanostructures formed in the volume of the crystals confirm the predictions made on the basis of positron annihilation spectroscopy studies. The model explaining the possible pores formation mechanism is proposed and validated by the results of luminescence measurements at 8 K.
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.
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The peculiarities of non-exponential degradation kinetics in topological-disordered solids are analyzed. It was shown that degradation transformations, described by ideal exponential function, are determined by one value of activation energy independently to the structural dispersivity of the system, while the non-exponential degradation kinetics corresponds to stretched or suppressed exponential-power-like relaxation function. The stretched degradation kinetics is proper to own degradation transformations in one-type systems. The degradation transformations, including two or more different elementary processes, are described by suppressed kinetics.
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