Unlocking the thermoelectric potential of the Ca₁₄AlSb₁₁ structure type

Area of Science:

• Materials Science
• Solid State Physics
• Energy Conversion

Background:

• Yb14MnSb11 and Yb14MgSb11 are established high-performance p-type thermoelectric materials exceeding 1200 K.
• Compounds with the Ca14AlSb11 structure type are known for their thermoelectric potential, but efficiency and stability vary.
• Yb14ZnSb11 was previously considered a poor thermoelectric material due to low power factor.

Purpose of the Study:

• To investigate the intrinsic thermoelectric properties of Yb14ZnSb11.
• To identify the cause of the previously reported low power factor in Yb14ZnSb11.
• To explore the potential of Yb14ZnSb11 and related Ca14AlSb11 structure compounds for high-temperature thermoelectric applications.

Main Methods:

• First-principles computations to analyze electronic structures and identify features for high thermoelectric performance.
• Synthesis of phase-pure Yb14ZnSb11 by developing a route that avoids impurity formation.
• Experimental characterization of thermoelectric properties, including the figure of merit (zT) at high temperatures.

Main Results:

• First-principles calculations indicated favorable electronic band structure features for thermoelectric performance in Yb14ZnSb11.
• The low power factor of Yb14ZnSb11 was attributed to an intrinsic Yb9Zn4+Sb9 impurity, not the material itself.
• Phase-pure Yb14ZnSb11 demonstrated exceptional high-temperature thermoelectric properties, achieving a peak zT of 1.2 at 1175 K.

Conclusions:

• The intrinsic thermoelectric performance of Yb14ZnSb11 is excellent, contrary to previous assumptions.
• The Ca14AlSb11 structure type universally possesses favorable electronic band structures for thermoelectric applications.
• This research opens avenues for developing novel high-performance thermoelectric materials based on the Ca14AlSb11 structure.