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[摘要]：The low-temperature photoluminescence (PL) of xPbO center dot (1 - x)SiO2 glasses (x = 0.20-0.75) was studied at T= 10 K. The recorded PL-spectra are a superposition of three spectral components with maxima located at 1.8 eV (identified as Pb 6p -> metal-bridging O2p radiative electron transition, the "R"-band), 2.0 eV (Pb 6p -> non-bridging O2p, the "O"-band) and 2.55 eV (Pb 6p -> Pb 6s, the "B"-band), respectively. It was found the essential link for "R", "O" and "B" PL-bands with chemical composition x of the glasses under study. These concentration dependences are expressed as mutual PL-intensity variations for each recorded luminescence band that allowed to determine their origin. The shape of established dependences well coincides with numerical data on NBO- and MBO-density of chemical bonding, reported previously. The overall PL-manner within the temperature range of 10-295 K is described by an empirical Street's law. It was shown that experimental photoluminescence quenching curves may be precisely approximated as a superposition of Mott relationships for nonequivalent luminescence centers. The obtained distribution of PL-centers on the activation energy for luminescence quenching reflects the essential donation of the low-energy states into the overall PL-process. The width of this energy distribution affects by the type of PL-emission band and the disordering degree in the arrangement of local PL-centers of a certain kind. (C) 2011 Elsevier B.V. All rights reserved. |
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