Design Principles and Experimental Evidence for Semiconducting Heusler Thermoelectrics by Vacancy-Filling

Area of Science:

• Materials Science
• Solid-State Physics
• Condensed Matter Physics

Background:

• Vacancy-filling strategy effectively expands the Heusler material family.
• Heusler semiconductors can be designed by controlling orbital energy gaps (t2g and eg).

Purpose of the Study:

• To design vacancy-filling Heusler semiconductors with semiconducting properties.
• To investigate the thermoelectric properties of non-stoichiometric TiFe$_{x}$Co$_{y}$Sb alloys.

Main Methods:

• Experimental synthesis of non-stoichiometric TiFe$_{x}$Co$_{y}$Sb Heusler alloys.
• Characterization of their semiconducting behavior and thermoelectric properties.
• Analysis of lattice thermal conductivity reduction due to site occupation.

Main Results:

• TiFe$_{x}$Co$_{y}$Sb alloys (2x + 3y = 3) exhibit p-type semiconducting behavior.
• Significantly reduced lattice thermal conductivity (κ$_{L}$) observed due to partial occupation of 4d sites.
• TiFeCo$_{0.33}$Sb achieved a low κ$_{L}$ of 2.77 W m$^{-1}$ K$^{-1}$ at room temperature.
• Optimal thermoelectric performance (figure of merit = 0.53 at 973 K) in TiFe$_{0.5}$Co$_{0.67}$Sb.

Conclusions:

• The vacancy-filling strategy is effective for designing semiconducting Heusler materials.
• TiFe$_{x}$Co$_{y}$Sb alloys show potential for enhanced thermoelectric applications.
• Tunable thermoelectric properties can be achieved through controlled non-stoichiometry.