Extraordinary n-Type Mg₃ SbBi Thermoelectrics Enabled by Yttrium Doping.

Area of Science:

• Materials Science
• Solid State Physics
• Inorganic Chemistry

Background:

• Advancing n-type magnesium antimonide (Mg₃ Sb₂) alloys for thermoelectric applications requires optimizing both carrier concentration and mobility.
• Current doping strategies, typically chalcogen doping, yield carrier concentrations below theoretical optima.
• Achieving large grain sizes is crucial for enhancing carrier mobility.

Purpose of the Study:

• To investigate the effect of yttrium doping on the cation site of Mg₃ Sb₂ alloys.
• To explore the resulting electronic transport properties and thermoelectric performance.
• To assess the potential of yttrium-doped Mg₃ Sb₂ as a high-performance n-type thermoelectric material.

Main Methods:

• Synthesis of Mg₃ Sb₂ alloys doped with yttrium on the cation site.
• Hot deformation and sintering techniques to promote large grain growth.
• Characterization of carrier concentration, carrier mobility, and thermoelectric figure of merit (zT).
• Analysis of electronic transport properties using a single parabolic band approximation.

Main Results:

• Yttrium doping achieved carrier concentrations exceeding 1 × 10²⁰ cm^-3, significantly higher than previous methods.
• Coarse-grain materials exhibited reasonably high carrier mobility.
• The thermoelectric figure of merit (zT) surpassed that of previously reported n-type Mg₃ Sb₂ and other n-type thermoelectrics in the 300-500 K range.

Conclusions:

• Yttrium is an effective dopant for significantly increasing carrier concentration in Mg₃ Sb₂ alloys.
• The optimized Mg₃ Sb₂ alloys demonstrate competitive thermoelectric performance, especially within the 300-500 K temperature range.
• These findings position Mg₃ Sb₂ alloys as a promising material for n-type thermoelectrics in sustainable energy applications.