Nonstoichiometric Fe-V-Al full Heusler alloys under high pressure: thermoelectric properties

The Heusler alloys are promising material for various applications, including thermoelectric power generators. There are several ways to improve their properties, among which the substitution of constituent elements, nanostructuring, temperature treatment, thin films engineering etc. This work is devoted to the experimental study of thermoelectric properties of Fe-V-Al-based Heusler alloys with different compositions under high pressure. The Seebeck coefficient and electrical resistance of several compounds were measured as a function of applied pressure up to 10 GPa at room temperature. The experimental results demonstrated a diversity of pressure responses of the thermoelectric properties that can be observed in chemically similar Heusler alloys under variation in their compositions. Moderate enhancing of the thermoelectric power factor, S-2/r (where S is the Seebeck coefficient and r is the electrical resistivity) was observed in Fe-rich Fe2.1V0.91Al0.99 compound at a pressure about similar to 1 GPa. It was found that all alloys with weak deviation from stoichiometric composition had a feature in their S (P) pressure behavior at P similar to 2 GPa which could be related to semimetal-metal phase transition.