Ba-filled Ni-Sb-Sn based skutterudites with anomalously high lattice thermal conductivity

Area of Science:

• Materials Science
• Solid State Chemistry
• Condensed Matter Physics

Background:

• Skutterudites are a class of intermetallic compounds known for their potential thermoelectric properties.
• The Ba-Ni-Sn-Sb system offers a unique platform to investigate the impact of filler atoms on thermoelectric performance due to its small cage structure.

Purpose of the Study:

• To synthesize and characterize novel filled skutterudites of the BaNi4Sb12-xSnx composition.
• To investigate the phase equilibria, structural properties, and thermoelectric behavior of these materials.
• To understand the influence of barium filler atoms on lattice thermal conductivity.

Main Methods:

• Arc melting and vacuum annealing for sample preparation.
• Electron Probe Microanalysis (EPMA) and X-ray Powder Diffraction (XPD) for phase analysis.
• Temperature-dependent electrical resistivity, Seebeck coefficient, and thermal conductivity measurements.
• Single crystal X-ray structure analysis, specific heat, Mössbauer spectroscopy, Resonant Ultrasonic Spectroscopy, and Vickers hardness tests.

Main Results:

• Successful synthesis of BaNi4Sb12-xSnx skutterudites with an extended homogeneity region.
• Observation of a crossover from metallic to semiconducting behavior in electrical resistivity.
• Reduced lattice thermal conductivity attributed to suppressed rattling of Ba filler atoms.
• Elastic moduli ranged from 100 GPa to 116 GPa, and thermal expansion coefficients were 11.8-13.8 × 10⁻⁶ K⁻¹.
• Vickers hardness values ranged from 2.6 GPa to 4.7 GPa, with no significant change after high-pressure torsion (HPT).

Conclusions:

• The Ba-Ni-Sn-Sb skutterudite system is well-suited for studying filler atom effects on phonon thermal conductivity.
• Suppressed rattling of Ba atoms leads to high lattice thermal conductivity.
• The synthesized materials show promising thermoelectric properties with potential for further optimization.