In-situ neutron investigation of hydrogen absorption kinetics in La(FexSi1−x)13 magnetocaloric alloys for room-temperature refrigeration application

• The deuterium absorption and desorption in La(Fe,Si)13 alloys are observed « in-situ » with neutron diffraction.
• The interstitial kinetics is successfully modeled with JMA law.
• Carbon addition effectively slows down deuterium interstitial kinetics and enhances stability of deuterium in host alloy.
• The changes in kinetics with carbon addition is attributed to changes in Fe–Fe bond lengths in the structure.

Promising magnetocaloric material La(Fe,Si)13 with a first-order magnetic transition has been widely investigated. The observed instability of hydrogen in the material is detrimental for its industrial upscale and a better control of the hydrogen absorption/desorption is necessary to optimize its application potential. In this article, the hydrogen absorption kinetics is studied through an in-situ neutron diffraction experiment. The results allow us to have an inside look at the structure “breathing” to accommodate the interstitial atoms and compare the effect of hydrides with carbohydrides.