Investigations on the thermoelectric properties of YbCo_2-xNi_xZn₂₀

Thermoelectric devices are both solid-state heat pumps and energy generators. Having a reversible process without moving parts is of high importance for applications in remote locations or under extreme conditions. Yet most thermoelectric devices have a rather limited energy conversion efficiency due to the natural competition between high electrical conductivity and low thermal conductivity, both being essential conditions for achieving a high energy conversion efficiency. Heavy-fermion compounds YbTM₂Zn₂₀ (TM = Co, Rh, Ir) have been reported to be potential candidate materials for thermoelectric applications at low temperatures [1]. Motivated by this result, we applied doping studies on the transition metal sites in order to optimize the carrier concentration as well as to promote more efficient phonon scatterings. We will present the latest investigation on the Ni-doped specimens YbCo_2-xNi_xZn₂₀, of which an enhanced thermoelectric figure of merit values have been obtained. Additionally, we will discuss the effect of doping Ni on improving the Seebeck coefficient values. We will also present a thermal evaluation of potential thermoelectric devices composed of these new materials.

[1] Wei, et. al. Sci. Adv. 5, eaaw6183 (2019).