A future hydrogen economy requires dense, safe, efficient and reversible hydrogen storage materials [1]. For mobile and in many cases also for stationary applications the volumetric and gravimetric density of hydrogen in a storage material is crucial. Metal hydrides and complex hydrides exhibit a great volumetric hydrogen density, of up to 150 kg m-3. Among those storage materials, the complex hydrides are promising candidates, as they can store up to 18 mass% hydrogen [2]. In this respect, Ca(BH4)2 has some potential, because the reversible hydrogen desorption and absorption at relatively moderate conditions has been demonstrated [3]. We propose to study the two different phases of Ca(BH4)2 as function of temperature.