Synthesis of CrxTi1−2xNbxO2O20≤x≤0.5 rutile solid solutions from alkoxides
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In this study, CrxTi1−2xNbxO2 (0 ⩽ x ⩽ 0.5) rutile solid solutions have been synthesized from gels built from hydrolysis-condensation of Cr (III) acetylacetonate, NbCl5 and Ti (IV) isopropoxide mixture (polymeric gel). Characterization of these solid solutions was carried out by X-ray diffraction, ultraviolet-visible and infrared spectroscopy, differential thermal and thermogravimetric analysis and CIELAB (Commission Internationale del'Eclairage L*a*b*) parameter measurements. The results obtained by the polymeric gel method were compared with those obtained by traditional ceramic synthesis. This comparison reveals some differences with regard to synthesis temperatures and reaction mechanisms. The formation of CrxTi1−2xNbxO2 (0 ⩽ x ⩽ 0.5) rutile solid solutions by the ceramic method requires temperatures of about 1200°C and soaking times of several days. These solid solutions are synthesized at 1000°C in 24 h by the polymeric gel method. In ceramic synthesis, the CrNbO4 compound with rutile structure appears as an intermediate compound in the formation of rutile solid solutions. In polymeric gel synthesis, however, the CrNbO4 rutile compound was not detected in the samples.
KeywordsSolid Solution Infrared Spectroscopy Rutile Thermogravimetric Analysis Reaction Mechanism
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