ENHANCED THERMOELECTRIC EFFICIENCY OF HALF-HEUSLER-FULL-HEUSLER COMPOSITE

Oshrat Appel ^1,2 Tal Zaharoni ¹ Ofer Beeri ³ Yaniv Gelbstein ¹

¹Department of Materials Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel
²Department of Physics, Nuclear Research Center Negev, Beer-Sheva, Israel
³Department of Materials Science, Nuclear Research Center Negev, Beer-Sheva, Israel

Thermoelectrics is known as one of the emerging renewable power generation technologies. Half-Heusler (HH) based semiconducting inter-metallic compounds show high potential as thermoelectric compositions due to the abundance of their elements in nature, their high mechanical and chemical stability, and their favorable electronic properties. Their main limitation lies in their high lattice thermal conductivity, κ_l. In the current research, the potential of κ_l reduction due to generation of composites based on phase separation of off-stoichiometric Ti_0.3Zr_0.35Hf_0.35Ni_1+δSn (δ=0.003, 0.005, 0.01) alloys into half- and full-Heusler (FH) composites was investigated. The excess Ni addition created a dramatic 52% reduction of the lattice thermal conductivity in the sample with δ=0.005, compared to the stoichiometric HH. This reduction is apparently attributed to the submicron precipitates of FH which scatter phonons. This κ_l reduction led to ZT of 0.97, one of the highest ZT values published so far for HH.