Half-Heusler compounds are one of the most promising candidates for thermoelectric materials for automotive and industrial waste heat recovery applications. In this talk, we will give an overview about our recent investigations in the material design of thermoelectric half-Heusler materials. Since the price for Hafnium was doubled within the last 2 years, our research focusses on the design of half-Heusler compounds without Hafnium. We will present a recent calculation on ZT per € and efficiency per € for various materials followed by our very promising results for n-type half-Heusler compounds without Hafnium resulting in 20 times higher ZT/€ values, which reduces the cost of TE materials used in a commercial TEG by 90%, entering an economical meaningful scenario. We will show how we adapted our knowledge from the n-type materials to design p-type Heusler compound without Hafnium exhibiting similar thermoelectric properties. We will present how we used phase separation to design thermoelectric highly efficient nano-composites of different single-phase materials. Since any high temperature TE material will only be suitable for the mass market if the material production and the module production is industrial upscalable, we will comment on various upscaling approaches, their challenges, and how one could tackle these challenges.
These results strongly underline the importance of phase separations as a powerful tool for designing highly efficient materials for thermoelectric applications that fulfill the industrial demands for a thermoelectric converter. Finally, we will discuss if and how the rather new topological materials and Weyl materials could have an impact in the thermoelectric material science and especially in the thermoelectric application scenarios.