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V.M. Khulugurov V.N. Salomatov I.M. Kalogeras A. Vassilikou-Dova I. Christakis 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):91-101
Thermally Stimulated Depolarisation Current (TSDC) and optical methods are applied to a range of alkali-fluoride crystals
in order to establish a model for the stable F
2
+
- like colour centres in LiF:OH-. The experimental results for LiF:OH- suggest that the OH- defects are partially destroyed under ionising irradiation or during crystal growth. The low-temperature dielectric relaxation
signals in LiF:OH- and LiF:Mg2+,OH- are attributed to highly interacting hydroxide ions and products of their destruction located in extended lattice defects.
In LiF:OH-, in contrast to other alkali halides, the results advocate for a defect-structure model, which considers a neutral defect
(ND, probably O2 or H2) sited at the anion vacancy of the O2--V
a
+
dipole and which possibly is the “nucleus” for the F
2
+
centre. The proposed F
2
+
(ND, O-) model seems to better explain the dielectric results, compared to the older F
2
+
(O2-) and F
2
+
(O-) models. The estimate for the electric dipole moment derived from the experimental TSDC bands, gives a value for the F
2
+
- like centre in LiF:OH- between those of the F
2
+
(O-) and F
2
+
(O2-) defects, in good agreement with the proposed F
2
+
(ND,O-) model. The reduction of the activation energy barrier of the (re)orientation process of the Mg2+V
c
-
(OH-) complexes in LiF:Mg2+,OH-, and the low-temperature shift of their TSDC band, compared to the single Mg
2
+
V
c
-
peak in LiF:Mg2+, are tentatively ascribed to an increase in the crystal-lattice parameters owing to the presence of OH- and/or products of its destruction.
Received 31 August 2001 / Received in final form 30 March 2002 Published online 9 July 2002 相似文献
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G. K. Zahariou E. Gavrielatos I. M. Kalogeras G. Athanasellis A. Vassilikou-Dova O. Igglessi-Markopoulou 《辐射效应与固体损伤》2013,168(6-12):1057-1062
The 3-acyl tetramic acids constitute a growing class of natural products displaying a range of biological activities. The g , g ' tricarbonyl moiety present in the 3-acyl tetramic acid provides a suitable site for bidentate complexation to a metal, which increases the biological activity. For the dielectric study of N-acetyl-3-butanoyl tetramic acid and a series of its complexes with Cu(II) and Co(II) in symmetric and asymmetric forms, we used the Thermally Stimulated Depolarization Currents (TSDC) technique. The drastic decrease of the intensity of the TSDC peaks of the symmetric and asymmetric complexes, compared to the above mentioned ligand, suggested that the polarizability of the side groups is considerably reduced. This result enhances the proposed complexation mode of the ligand through oxygen next to carbons 3 and 4 of the 5-member ring. 相似文献
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