Magnetic and optical studies of chromium oxides. Part 2.—Calcination of chromic chloride supported on alumina

Abstract

Magnetic and optical studies were made on chromium (III) chloride supported at various concentrations on a porous alumina, the impregnated samples having been calcined at different temperatures between 50–1150°C. The measurement of magnetic susceptibility and electron paramagnetic resonance spectra was carried out at controlled temperatures from –196 to 300°C. Optical reflectance spectra were obtained at room temperature on selected samples. The results suggest that clustering of the chromium chloride occurs, even in the lowest concentration studies (1.5 wt.% Cr); heat treatment in air leads to the formation of a mixed oxide phase containing Cr^VI, the stability of which is discussed in terms of electron transfer between the support and the chromium species.