Electron Paramagnetic Resonance Study of W5+ Pairs in Lithium—Tungsten PhosphateGlasses

Rakhimov, R.R.; Jones, D.E.; Rocha, H.L.; Prokof\textquotesingleev, A.I.; Aleksandrov, A.I.

Авторы: Rakhimov Rakhim R., Jones David E., Rocha Heiddy L., Prokof\textquotesingleev Alexander I., Aleksandrov Aleksey I.
Журнал: Journal of Physical Chemistry B
Том: 104
Номер: 47
Год издания: 2000
Издательство: American Chemical Society
Местоположение издательства: United States
Первая страница: 10973
Последняя страница: 10977
DOI: 10.1021/jp000150w
Аннотация: The electron paramagnetic resonance (EPR) spectra of W5+ ions in Li2O-WO3-P2O5 glasses with differentcomposition of oxide components have been investigated. The anisotropy of the axially symmetric g factordecreases with an increase of Li content in the glass and with an increase in temperature. Evidence for theformation of W5+ ion pairs has been obtained by using a dual-mode EPR cavity that allows measuring EPRspectra with polarization of the magnetic vector B1 of the microwave perpendicular or parallel to the staticmagnetic field B0. Enhancement of the relative intensity of the half-field ∆MS ) 2 spin transition was observedat B1||B0. The ratio R of the intensity of the ∆MS ) 2 transition to the intensity of the ∆MS ) 1 transition wasused to describe the effectiveness of pair formation between W5+ ions in the glass and to determine the meandistances r between W5+ ions. The parameter R increases with an increase of Li2O content in the glass. Thisshows that the inclusion of Li+ ions favors the formation of tungsten pairs. The mean distance between W5+ions decreases from r ) 4.53 Å for the glass without Li+ ions to r ) 3.70 Å for the glass containing 50 mol% Li2O. Disproportionation of W5+ ions in the pair is thermally reversible in the presence of Li+ ions suchthat temperature decrease shifts the equilibrium toward the formation of W4+ and W6+ ions.
Добавил в систему: Александров Алексей Иванович

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Electron Paramagnetic Resonance Study of W5+ Pairs in Lithium—Tungsten PhosphateGlassesстатья

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