On the Phase Separation in n-Type Thermoelectric Half-Heusler Materials

Abstract

Half-Heusler compounds have been in focus as potential materials for thermoelectric energy conversion in the mid-temperature range, e.g., as in automotive or industrial waste heat recovery, for more than ten years now. Because of their mechanical and thermal stability, these compounds are advantageous for common thermoelectric materials such as Bi2Te3, SiGe, clathrates or filled skutterudites. A further advantage lies in the tunability of Heusler compounds, allowing one to avoid expensive and toxic elements. Half-Heusler compounds usually exhibit a high electrical conductivity σ, resulting in high power factors. The main drawback of half-Heusler compounds is their high lattice thermal conductivity. Here, we present a detailed study of the phase separation in an n-type Heusler materials system, showing that the TixZryHfzNiSn system is not a solid solution. We also show that this phase separation is key to the thermoelectric high efficiency of n-type Heusler materials. These results strongly underline the importance of phase separation as a powerful tool for designing highly efficient materials for thermoelectric applications that fulfill the industrial demands of a thermoelectric converter.

Advances in half-Heusler alloys for thermoelectric power generation

“…Recent work using unfolded supercell calculations has shown that new bands can emerge in substituted HH compositions (e.g. in vacancy systems, 170 for interstitials 58 and complex compositions 233 ) and this is another possible route for performance improvements. This is an area where theory could lead experiments by identifying new compositions with promising electronic bandstructures.…”

Band Structure Modification and Mass Fluctuation Effects of Isoelectronic Germanium-Doping on Thermoelectric Properties of ZrNiSn

“…In the past few decades, the exploration of renewable/alternative energy technologies has been accelerated to minimize the dependency of human activities on fossil fuels, which are deeply responsible for global warming, air pollution, and climate changes, etc. More than two-third part of the energy produced in our economy is wasted in the form of heat . If even a small part of this waste heat can be utilized, then it would lead to reducing the consumption of non-renewable sources of energy and may be helpful in limiting climate changes to an extent.…”

“…More than two-third part of the energy produced in our economy is wasted in the form of heat. 1 If even a small part of this waste heat can be utilized, then it would lead to reducing the consumption of nonrenewable sources of energy and may be helpful in limiting climate changes to an extent. Thermoelectrics (TEs) offer a prospective means for energy harvesting or waste heat recovery.…”

Band Structures and Transport Properties of High-Performance Half-Heusler Thermoelectric Materials by First Principles

“…It is also worth mentioning that first-principles calculations have provided the guideline for developing new promising HH-based TE materials. Up to now, experimental investigations on HH compounds have mainly focused on n-type M NiSn [ 30 , 31 , 32 , 33 , 34 ]. There is only a very small fraction of studies on other HH systems [ 35 , 36 ].…”