Revealing the Defect-Dominated Electron Scattering in Mg₃Sb₂-Based Thermoelectric Materials

Area of Science:

• Materials Science
• Solid State Physics
• Condensed Matter Physics

Background:

• Thermoelectric properties depend on electron and phonon transport.
• Carrier scattering mechanisms critically influence electron transport and material electrical properties.
• Defect scattering significantly affects room-temperature electron mobility in n-type Mg3Sb2 materials, but its origin is debated.

Purpose of the Study:

• To investigate the origin of defect scattering mechanisms in n-type Mg3Sb2-based thermoelectric materials.
• To elucidate the relationship between point defects, chemical composition, and synthesis conditions.
• To confirm the role of point defect scattering in the electrical conductivity.

Main Methods:

• Synchrotron powder X-ray diffraction to identify Mg vacancies and Mg interstitials.
• Systematic variation of synthesis conditions to correlate point defects with composition.
• Neutron irradiation to introduce point defects independently of grain size.
• Analysis of electrical conductivity changes post-irradiation.

Main Results:

• Mg vacancies and Mg interstitials were identified as key point defects.
• A clear link was established between synthesis conditions, chemical composition, and point defect concentration.
• Neutron irradiation reproduced thermally activated electrical conductivity, confirming defect scattering's impact.
• Point defect scattering was confirmed as a dominant factor in electron transport.

Conclusions:

• Point defects, particularly Mg vacancies and interstitials, are the primary cause of electron scattering in n-type Mg3Sb2.
• Understanding and controlling these defects is crucial for optimizing thermoelectric performance.
• This research clarifies a long-standing controversy regarding defect scattering mechanisms.