Structure and Transport Properties of the BiCuSeO-BiCuSO Solid Solution

Area of Science:

• Materials Science
• Solid State Chemistry
• Thermoelectrics

Background:

• Bismuth copper oxychalcogenides (BiCuSeO and BiCuSO) are promising thermoelectric materials.
• Understanding the impact of chalcogen substitution (Se to S) on their properties is crucial for optimizing performance.

Purpose of the Study:

• To investigate the crystal structure and electrical/thermal transport properties of the BiCuSe$_{1-x}$S$_{x}$O solid solution series.
• To determine the effects of sulfur substitution on the band gap, bonding, and defect scattering mechanisms.

Main Methods:

• Synthesis and characterization of the BiCuSe$_{1-x}$S$_{x}$O series.
• Analysis of crystal structure evolution with varying sulfur content.
• Measurement of electrical resistivity and thermal conductivity.

Main Results:

• A complete solid solution was confirmed between BiCuSeO and BiCuSO.
• Band gap increased linearly from 0.8 eV to 1.1 eV with increasing sulfur content.
• Thermal conductivity decreased significantly due to point defect scattering, while electrical resistivity strongly increased.

Conclusions:

• Sulfur substitution in BiCuSeO leads to a tunable band gap and reduced thermal conductivity.
• Increased electrical resistivity is attributed to changes in copper vacancy formation energy.
• Challenges exist in obtaining sulfur-rich samples due to stability and volatilization issues.