Layered Ordered Multianion Semiconductor Bi₁₈O_21.6Se_1.8Cl_7.2 with Low c-Axial Thermal Conductivity

Area of Science:

• Materials Science
• Solid State Chemistry
• Crystallography

Background:

• Layered ordered multianion materials possess tunable properties due to complex interactions.
• Understanding structure-property relationships in these materials is key for designing new compounds.

Purpose of the Study:

• To synthesize and characterize a novel layered quaternary compound, Bi18O21.6Se1.8Cl7.2.
• To investigate the electronic and thermal transport properties of this new material.

Main Methods:

• Single crystal growth and structural analysis.
• Measurement of electronic band gap and carrier type.
• Determination of axial thermal conductivity.

Main Results:

• A novel layered quaternary compound, Bi18O21.6Se1.8Cl7.2, was successfully synthesized.
• The material exhibits semiconducting behavior with an indirect band gap of approximately 1.51 eV and dominant electron-type carriers.
• Exceptionally low c-axial thermal conductivity (0.261–0.307 W m⁻¹ K⁻¹) was observed at room temperature.

Conclusions:

• The strategic design of layered materials by combining distinct building blocks with varied anionic environments is an effective strategy.
• Bi18O21.6Se1.8Cl7.2 expands the known phase space for ultralow-thermal-conductivity materials in the Bi-O-Se-Cl system.
• This discovery opens new avenues for developing materials with tailored thermal and electronic properties.