Crystal structure and in situ decomposition of Eu(BH<inf>4</inf>)<inf>2</inf> and Sm(BH<inf>4</inf>)<inf>2</inf>

Abstract

Synthesis of halide free rare earth metal (RE) borohydride complexes is demonstrated by the metathesis reaction of trivalent RE metal chlorides and LiBH<inf>4</inf> in ethereal solution, combined with solvent extraction using dimethyl sulfide. The crystal structures of Eu(BH<inf>4</inf>)<inf>2</inf> and Sm(BH<inf>4</inf>)<inf>2</inf> are orthorhombic (space group Pbcn) and are shown to be related to the structure of Sr(BH<inf>4</inf>)<inf>2</inf> by Rietveld refinement. Further, the thermal decomposition of these materials has been studied by in situ synchrotron radiation powder X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, mass spectrometry and Sieverts measurements. The decomposition pathway of these solvent extracted materials has been compared against materials prepared by mechano-chemistry, the process of which is simplified by the absence of chloride impurities. This journal is