Insight into mechanical properties and thermoelectric efficiency of Zr₂CoZ (Z  =  Si, Ge) Heusler alloys

We investigated the electronic, mechanical and thermoelectric properties of Zr₂CoZ (Z  =  Si, Ge) Heusler alloys using the first-principles calculation. From the analysis of various elastic constants, the shear and Young's moduli, Poisson's ratio, the ductile nature of the alloys is predicted. Thermoelectric coefficients viz., Seebeck, electrical conductivity and figure of merit show Zr₂CoZ alloys as n-type thermoelectric materials showing linearly increasing Seebeck coefficient with temperature. The value of total absolute Seebeck coefficients at 1200 K of Zr₂CoSi and Zr₂CoGe are 60 µV K⁻¹ and 40 µV K⁻¹ respectively mainly because of the existence of almost flat conduction bands along L to Г directions of high symmetry Brillouin zone. Further, the chemical potential variation of power factor confirms the n-type doping fruitful to increase their TE performance. The figure of merit achieves an upper-limit of 0.95 at 850 K and can favour their use for waste heat recovery at higher temperatures and thermoelectric spin generators. (paper)