High-temperature electronic transport of Ru2Ti(Si,Al) Heusler compounds

Context

Heusler compounds with six valence electrons per atom have attracted interest as thermoelectric materials owing to their semimetallic and semiconducting properties.
Here, we theoretically and experimentally investigate electronic transport in Ru2TiSi-based full-Heuslers.
We show that electronic transport in this system can be well captured by a two-parabolic-band model.
The larger band gap of Ru2TiSi promises a higher thermoelectric performance, compared to its isovalent family member Fe2VAl, which has been studied as a thermoelectric material for over two decades.
Additionally, we identify p-type Ru2TiSi as far more efficient than previously studied n-type compounds and demonstrate that this can be traced back to much lighter and more mobile holes originating from dispersive valence bands.
Our findings suggest that an exceptionally high dimensionless figure of merit zT > 1 can be realized in these p-type compounds around 700 K upon proper reduction of the lattice thermal conductivity, e.g., by substituting Zr or Hf for Ti.

Technical details

Temperature-dependent thermoelectric properties (Seebeck coefficient and electrical resistivity).
Temperature is given in kelvins, Seebeck coefficient in microvolts per kelvin and resistivity in microohms*centimeter.