Atomic interactions in the p-type clathrate I Ba8Au5.3Ge40.7

Area of Science:

• Solid State Chemistry
• Materials Science
• Crystallography

Background:

• Clathrate materials are of interest for thermoelectric applications.
• Understanding the structure-property relationships in novel clathrates is crucial for material design.

Purpose of the Study:

• To synthesize and characterize single crystals of Ba(8)Au(5.3)Ge(40.7).
• To investigate the crystal structure, chemical bonding, and thermoelectric properties of this compound.
• To explore the potential for tuning thermoelectric performance in the Ba-Au-Ge system.

Main Methods:

• Single crystal X-ray diffraction for structural refinement.
• Electron localizability indicator (ELI) for chemical bonding analysis.
• Measurement of electrical conductivity, Seebeck coefficient, and thermal conductivity to determine thermoelectric figure of merit (ZT).

Main Results:

• Single crystals of Ba(8)Au(5.3)Ge(40.7) were successfully synthesized via the Bridgman technique.
• The crystal structure revealed no vacancies, with direct Ba-Au interactions identified.
• The material exhibits p-type conductivity, low lattice thermal conductivity (≈0.6 W m⁻¹ K⁻¹ at 500 K), and a ZT of 0.3 at 511 K (single crystal) and 0.9 at 680 K (polycrystalline sample).

Conclusions:

• Ba(8)Au(5.3)Ge(40.7) is a diamagnetic, p-type semiconductor with excellent thermoelectric potential.
• The identified direct Ba-Au bonding influences the material's properties.
• Compositional tuning offers a pathway to optimize thermoelectric performance in Ba-Au-Ge clathrates.