Distinct impact of order degree on thermoelectric power factor of p-type full-Heusler Mn2VAl compounds

Abstract

Full-Heusler compounds have three crystal structures with a different order degree; the highly ordered L2 _1 , partially disordered B2, and completely disordered A2 structures. To reveal the effects of the order degree on thermoelectric (TE) properties of the full-Heusler compounds, Mn _2 VAl samples with varied L2 _1 and B2 order degrees are prepared by changing preparation conditions, and their Seebeck coefficients and electrical conductivities are measured in a wide temperature range. As the B2 order degree becomes higher, the Seebeck coefficient increases, leading to the increase of the power factor (PF). The maximum PF is 2.84 × 10 ^−4 Wm ^−1 K ^−2 at 767 K for the Mn _2 VAl sample with the highest B2 order degree. This study demonstrates that the TE properties of Mn _2 VAl can be enhanced by increasing the fraction of the B2 phase. A relation between the Seebeck coefficient and crystal structures is also discussed based on the calculation of the electronic density of states of Mn _2 VAl with the L2 _1 and B2 structures.

Keywords

• full-Heusler
• Mn2VAl
• order degree
• electronic density of states
• thermoelectric properties