Five coordinated Mn in Ba₄Mn₂Si₂Te₉: synthesis, crystal structure, physical properties, and electronic structure

Area of Science:

• Solid-state chemistry
• Materials science
• Crystallography

Background:

• Quaternary chalcogenides are promising materials for various applications.
• Understanding the structure-property relationships in novel materials is crucial for technological advancement.

Purpose of the Study:

• To synthesize and characterize a new transition metal-containing quaternary chalcogenide, Ba4Mn2Si2Te9.
• To investigate its structural, electronic, and thermal properties.

Main Methods:

• Solid-state synthesis at 1273 K.
• Single-crystal X-ray diffraction for structural determination.
• Optical absorption, resistivity, and thermal conductivity measurements.
• Density Functional Theory (DFT) calculations.

Main Results:

• Single-crystals of Ba4Mn2Si2Te9 were successfully synthesized.
• The material crystallizes in the orthorhombic system (Pbam) with disordered Mn sites.
• It exhibits semiconducting behavior with a direct bandgap of 0.6(1) eV.
• Extremely low thermal conductivity (κ) was observed, decreasing with increasing temperature.
• DFT studies indicate bandgap dependence on magnetic ordering.

Conclusions:

• Ba4Mn2Si2Te9 is a novel quaternary chalcogenide with a unique crystal structure.
• Its semiconducting nature and exceptionally low thermal conductivity suggest potential for thermoelectric applications.
• Further studies on magnetic ordering and thermoelectric performance are warranted.