Estudo da análise térmica do hexahidrato de nitrato de lantânio La(NO3)3•6H2O

Abstract

Thermal decomposition of lanthanum nitrate hexahydrate, La(NO3)3∙6H2O, has been studied by thermogravimetric technique, differential scanning calorimetry, infrared spectroscopy and X-ray diffractometry. At the beginning, this complex process involves slow and rapid internal hydrolysis in the liquid phase, like the processes described for the light members of the lanthanide series. In the first stage, condensation is accompanied by the removal of water to form intermediate clusters containing O-La-OH groups. No traces of lower hydrates were detected. It is assumed that the existence of intermediate compounds with six atoms of lanthanum best fits the experimental data. At higher temperatures, these products undergo further thermal degradation, releasing nitric acid, nitric acid azeotrope, nitrogen dioxide, water, and oxygen. Finally, after having lost remaining interstitial water, the material is transformed into a hexagonal La2O3. All mass losses are taken into account satisfactorily for under the proposed mechanism of thermal decomposition.