High ZT of new half-Heusler LiXZ (X=La, Y and Z=Ge, Si) alloys at room temperature

Abstract

The thermoelectric, electronic and structural properties of novel half- Heusler (HH) LiXZ (X = La, Y; Z = Ge, Si) alloys are researched using the full-potential linearized augmented plane wave (FP-LAPW) method and semi-classical Boltzmann transport theory under the constant time relaxation. Our results reveal that all alloy can be experimentally synthesized due to they have exhibited energetic, mechanical and dynamic stability. In addition, all these systems present semiconducting behaviour with a flatness band near Fermi energy (EF) level, which makes its favourable for thermoelectric compounds. The calculated thermoelectric properties show that LiLaZ is highest p-type thermo power. However, LiYZ is highest n-type thermo power performance. The Seebeck coefficients are higher than at room temperature of thermoelectric Bi2Te3. The conductivity is considerably low of LaLiGe and LiYSi. The higher values of figure of merit (ZT) and power factor of LiXZ half-Heusler alloys make them promising for high-performance thermoelectric applications resulting from the favourable features of their band structure and high mechanical stability.