The half-Heusler compounds have distinctive properties and high tunability which makes the class very promising as thermoelectric materials. A study has predicted that there can be as many as 481 stable half-Heusler compounds using high-throughput ab initio calculation combine with machine learning techniques. The particular half-Heusler compounds of interest as thermoelectric materials (space group ) are the semiconducting ternary compounds with a general formula XYZ where X is a more electropositive transition metal (such as Ti or Zr), Y is a less electropositive transition metal (such Ni or Co), and Z is heavy main group element (such as Sn or Sb). This flexible range of element selection allows many different combinations to form a half-Heusler phase and enables a diverse range of material properties.
Half-Heusler thermoelectric materials have distinct advantages over many other thermoelectric materials; low toxicity, inexpensive element, robust mechanical properties, and high thermal stability make half-Heusler thermoelectrics an excellent option for mid-high temperature application. However, the high thermal conductivity, which is intrinsic to highly symmetric HH structure, has made HH thermoelectric generally less efficient than other classes of TE materials. Many studies have focused on improving HH thermoelectric by reducing the lattice thermal conductivity and zT > 1 has been repeatedly recorded.