Zintl Chemistry for Designing High Efficiency Thermoelectric Materials

TLDR

Zintl phases, including Yb14MnSb11, clathrates, and filled skutterudites, exhibit high zT and, because of their rich chemistry, allow chemical substitutions and structural modifications that tune carrier concentration, mobility, effective mass, and lattice thermal conductivity, enabling their transport properties to be described by traditional heavily doped semiconductor models. In Zintl thermoelectrics, free carrier concentration is set by valence imbalance, enabling rational zT optimization, while low thermal conductivity results from point defect scattering and the low velocity of optical phonon modes. The transport properties of many modern thermoelectrics can be understood using traditional models for heavily doped semiconductors.

Abstract

Zintl phases and related compounds are promising thermoelectric materials; for instance, high zT has been found in Yb14MnSb11, clathrates, and the filled skutterudites. The rich solid-state chemistry of Zintl phases enables numerous possibilities for chemical substitutions and structural modifications that allow the fundamental transport parameters (carrier concentration, mobility, effective mass, and lattice thermal conductivity) to be modified for improved thermoelectric performance. For example, free carrier concentration is determined by the valence imbalance using Zintl chemistry, thereby enabling the rational optimization of zT. The low thermal conductivity values obtained in Zintl thermoelectrics arise from a diverse range of sources, including point defect scattering and the low velocity of optical phonon modes. Despite their complex structures and chemistry, the transport properties of many modern thermoelectrics can be understood using traditional models for heavily doped semiconductors.