Paramagnetic Ge–Li centres in alpha quartz revisited: The DLi([GeO4/Li]0D) centre

2008 ◽  
Vol 86 (11) ◽  
pp. 1303-1311
Author(s):  
R F.C. Claridge ◽  
O M Kryliouk ◽  
J A Weil ◽  
J A.S. Williams
Keyword(s):  
Electron Paramagnetic Resonance Spectroscopy ◽  
Spin Hamiltonian Parameter ◽  
Resonance Spectroscopy ◽  
Paramagnetic Defect ◽  
Paramagnetic Resonance ◽  
Hamiltonian Parameter ◽  
X Band ◽  
X Irradiation ◽  
And Storage ◽  
Electron Paramagnetic

A previously unreported stable paramagnetic defect centre in single-crystal alpha-quartz has been studied by quantitative X-band electron paramagnetic resonance spectroscopy at 15, 100, and 296 K, and is shown to contain a Ge3+ ion, presumably located substitutional for Si4+, with a nearby interstitial Li+ ion. The centre, called DLi herein, grows in slowly (months) after room-temperature x-irradiation and storage. Hyperfine structure arising from 73Ge, 7Li, and 29Si has been observed. The spin-Hamiltonian parameter matrices g, A(7Li), A(73Ge), and P(73Ge) are reported, also for centre CLi. A thermal dynamic process, probably involving Li+ hopping, begins to be appreciable above 100 K. Discussion of DLi, its apparent growth from another paramagnetic centre (not yet fully characterized), and comparison with other similar defects is included.PACS Nos.: 42.70.Ce, 61.72.Hh, 61.72–y, 61.72S–, 61.72uf, 61.80–x, 76.30–v, 76.30.Mi

The behaviour of a synthetic 57Fe-doped kaolin: Mössbauer and electron paramagnetic resonance studies

Clay Minerals ◽  
1980 ◽  
Vol 15 (4) ◽  
pp. 429-444 ◽  
Author(s):  
A. H. Cuttler
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Ferric Oxide ◽  
Ferrous Iron ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
X Irradiation ◽  
Epr Signal ◽  
Signal Changes ◽  
Electron Paramagnetic

AbstractThe thermal behaviour of a ferrous doped kaolin has been studied by Mössbauer spectroscopy and electron paramagnetic resonance spectroscopy. From the observations it is concluded that the iron substitutes trioctahedrally as Fe2+ in the ‘gibbsite-like’ sheet in place of dioctahedral aluminium. The g = 2 EPR signal is shown to be associated with these ferrous ‘cells’ which appear to occur in clusters. It is suggested that these ferrous cells are trapped within the normal dioctahedral aluminium structure. Dehydroxylation of the ferrous iron cells takes place between 623 and 673 K leading to the formation of an iron-rich pyroxene and, by 723 K, a ferric oxide. At temperatures > 723 K the pyroxene itself oxidizes to a second ferric oxide. The EPR signal changes at 623 K and disappears at 723 K. The signal is attributed to a trapped hole induced by X-irradiation, located near a silicon atom on the boundary between normal dioctahedral cells and trioctahedral Fe2+ cells. It is possible to extend the model to explain some puzzling features concerning the g = 2 EPR signals reported by other authors and to propose other effects which might result from the presence of these cells.

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