Calorimetric determination of the heat capacity function and absolute entropy of yttrium borohydride (Y(BH4)3) mechanochemically prepared

Abstract

Over the last two decades, complex metal hydrides have attracted attention in various fields such as chemical hydrogen storage, solid state electrolytes and superconductivity. In this context, we determined thermodynamic properties of the complex metal hydride Y(BH₄)₃. Yttrium borohydride was prepared by solid state metathesis yielding a mixture containing three equivalents lithium chloride beside the boranate. The benefit of the mechanochemical preparation procedure compared to the classical wet chemical one is to avoid the desolvation step which can lead to a partial decomposition of the hydride. The heat capacity of the compound as a function of the temperature covering a temperature range from 2 K to 370 K was determined using two different calorimetric techniques. Based on the heat capacity data, the standard entropy at 298.15 K was obtained. From the evaluation of the low temperature heat capacity region the Sommerfeld coefficient and the Debye temperature were derived.