A study of the thermal decomposition of hydrated europium(III) chloride and europrium(III) bromide

Abstract

The thermal decompositions of EuCl 3·6 H 2O and EuBr 3· 6 H 2O have been studied and compared in the temperature range ambient to 900°C. The techniques used were thermogravimetric analysis supported by chemical analysis, Mössbauer spectroscopy, mass spectrometry and infrared spectrophotometry applied to intermediate decomposition products. When heated in a slow stream of nitrogen, water is lost in stages, which are better defined in the chloride than in the bromide system, up to 350° and 390°C, respectively, above which temperatures the corresponding oxide halide is the only major product. At least part (about 30%) of the europium undergoes a valence change to europium(II) in the bromide system but not in the chloride system in the course of removal of water which occurs by dehydration and hydrolytic processes. The bromide system is thus intermediate between the corresponding chloride and iodide systems since the latter appears to undergo a complete, or near complete, transformation to europium(II). The oxide chloride and oxide bromide are converted to europium(III) oxide at 900 and 910°C, respectively.