Substitutional and interstitial modulation of La-Fe-Si structure discussed with hydrogen sorption kinetics.

Magnetocaloric materials (La,Ce)(Fe,Mn,Si)13Hx have great potential as commercializable candidate for room-temperature magnetic refrigeration technology. It is important to have a better understanding of their hydrogen stability for the industrial upscaling. The hydrogenation reaction is investigated by powder neutron diffraction in order to have insights on the interaction between hydrogen and the host lattice. The reaction kinetics of absorption and desorption of interstitial elements can be influenced by presence of other interstitial and substitutional atoms. We demonstrate with neutron diffraction data the effects of C and Ce atoms on the deuterium absorption and desorption kinetics. The influence of substitutions and interstitial modification to the crystal structure are discussed at the level of interatomic Fe-Fe bond variations.