through Charge Carrier Tunning*

There is a growing interest in utilizing waste-heat recovery units to enhance the efficiency of energy processes, and thermoelectric generators (TEGs) are sound candidates since they convert heat directly into electricity by using the Seebeck effect. Extensive studies have been conducted to make TEGs feasible in reality, but thermoelectric technology is still far from being widely employed in practical applications due to the low figure of merit (ZT) for most thermoelectric materials. However, promising low-temperature thermoelectric properties have been reported for single crystals of YbTM₂Zn₂₀ (TM = Co, Rh, Ir) [1, 2]. Here we report a detailed study on the effect of charge carrier tuning for the YbCo₂Zn₂₀ compound. Guided by the Hall effect measurement, we are able to quantitively dope on the Co site. This leads to improved electrical properties as well as enhanced ZT values. In addition, more efficient phonon scatterings are achieved through this approach which lowers the lattice thermal conductivity for these materials.

 

[1] Mun et al., Phys. Rev. B 86, 115110 (2012).

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