Structural and electrical properties of calcium and strontium hydrides

The conductivity behaviour and structure of CaH2 and SrH2 have been studied and compared to the behaviour of samples reacted with a monovalent hydride, NaH. The created hydride ion vacancies are expected to enhance hydride ion conductivity and give more insight into the conduction mechanism. The observed conductivity behaviour is correlated with structural data obtained from neutron powder diffraction on both undoped and doped hydride materials. It was found that only small amounts of sodium could be doped on the Ca/Sr sites in the hydride lattices, namely similar to 0.1 mol%. Despite the low solubility, the formation of hydride ion vacancies has a significant effect on the conductivity behaviour of SrH2, most importantly enhancing the low temperature hydride ion conductivity. The formation of hydride ion vacancies does not seem to enhance the ionic conductivity in CaH2