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Preparation and Some Properties of Lithium Vanadium Bronzes

El-Sayed A., Mousa S.

Polish Journal of Chemistry

2006

Vol. 80, nr 5

773-781

Lithium vanadium bronzes with composition formula LixV2O5 (0.04 _ x _ 0.92) have been prepared by solid-state reaction at 650graduate C in argon atmosphere. The obtained products were characterized by X-ray powder diffraction and IR spectroscopy. The results reveal that four phases are present in the range from x = 0.04 to 0.92 namely alfa,beta ,beta' , and gamma phase. The magnetic susceptibility for the investigated samples was measured using the conventionalGouy'smethod. The effectivemagnetic moments as calculated from experimental data indicate the presence ofV4+ ions in all samples. The electrical conductivity as a function of temperature and lithium content was measured from room temperature to 483 K. The electrical conductivity of the samples is found to be affected by lithium content. The electrical conductivity increases with temperature and both electronic and ionic conduction are discussed.

Some Properties of Sodium Tungsten Bronzes as a Function of Sodium Concentration

El-Sayed A., Mousa S.

Polish Journal of Chemistry

2005

Vol. 79 / nr 7

1135-1142

Sodium tungsten bronzes, NaXWO3 have been prepared ranging in composition from x = 0.25 to 0.85 by solid state reaction at 850°C in argon atmosphere. X-ray diffraction and IR absorption spectra were used to characterize the structure of the product samples. It was found two distinct phases in the range from x = 0.25 to 0.85, tetragonal and cubic structure. The reflectance measurements in the range from 300 to 780 nm have been performed by diffuse reflection method. The reflectivity increased with sodium concentration and it was found above 70% for the sample with higher sodium content (x = 0.85). The electrical conductivity (_) has been measured as a function of sodium concentration and temperature from 300 to 550 K. The conductivity was found to increase with increasing sodium concentration and decrease with temperature for the prepared samples.