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EXAFS/XANES studies of the local structure of amorphous ionic and electronic-ionic conductors

Wasiucionek M., Garbarczyk J., Bacewicz P., Jóźwiak J, Nowiński J.L.

Materials Science Poland

2006

Vol. 24, No. 1

181--186

X-ray absorption spectroscopy methods such as EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-ray Absorption Near Edge Structure) are sophisticated and effective tools for studying the local structure of many solids and liquids. Their use is particularly valuable in the case of amorphous systems, in which due to the absence of long-range order the possibilities of structure determination by diffraction methods are limited. EXAFS and XANES have been extensively used to study the local structure of many electrically conducting (via ions, electrons, or both electrons and ions) solids. The special merit of the latter studies is that their results reveal the short-range structure of these conductors, which is an important factor determining their transport properties. The paper reports recent results of EXAFS/XANES studies on the local structure of selected electrically conducting glasses of the Li2O-V2O5-P2O5 system and their silver analogues. All spectra were acquired at the K-edge of vana

Polarographic determination of V(IV)/V(V) ratio in vanadate glasses

El-Askalany A. H., Khalifa M. E., Nawar N., El-Defrawy M. M.

Chemia Analityczna

2000

Vol. 45, No. 1

117-124

Polarographic reduction of vanadate and vanadyl ions in the presence of 0.4 mol 1(-1) Na(2)SO(4), 0.016 mol 1(-1) H(2)SO(4) and 8 x 10(-1) mol 1(-1 ) ethylenediaminetetraacetic acid disodium salt (EDTA) has been investigated by direct current (DC) and direct current tast (DCT) polarographic techniques. Two waves were obtained. The first wave corresponds to the reduction of V(V) to V(IV) and the second wave is due to the reduction of V(IV) to V(III). The constancy of Id/C makes the microdetermination of both V(IV) and V(V) possible. The effects of different anions and cations on DC and DCt polarographic waves were studied. A proposed procedure has been elaborated and applied successfully for the determination of V(IV)/V(V) ratio in vanadate glasses.

Badano polarograficzną redukcję wanadu w obecności 0.4 mol 1(-1) Na(2)SO(4) i 8 x 10(-3) mol 1(-1) Na2EDTA. Otrzymano dwie fale odpowiadające redukcji V(V) do V(IV) i V(IV) do V(III). Zbadano także wpływ różnych anionów i kationów na wysokość fal wanadu. Zaproponowano procedurę oznaczenia V(V) i V(IV) w szkłach wanadowych.