Chemical Pressure Induced Efficient Carrier Concentration Optimization for High Thermoelectric Performance in SmS

Area of Science:

• Materials Science
• Solid State Physics
• Thermoelectrics

Background:

• Carrier concentration is crucial for optimizing thermoelectric materials.
• Conventional aliovalent doping has limitations in modulating carrier concentration.
• Samarium sulfide (SmS) is a promising n-type thermoelectric material with a mixed valence state.

Purpose of the Study:

• To explore a novel strategy for modulating carrier concentration in thermoelectric materials.
• To investigate the effect of local chemical pressure on carrier concentration in SmS.
• To enhance the thermoelectric performance of SmS through targeted doping.

Main Methods:

• Introducing local chemical pressure by doping SmS with different elements.
• Comparing the efficacy of Y doping versus Sc doping on carrier concentration.
• Analyzing the change in Sm valence state induced by Y doping.
• Measuring the thermoelectric power factor at elevated temperatures.

Main Results:

• Y doping provides 6-12 times more electrons than Sc doping at equivalent concentrations.
• Y doping induces significant local chemical pressure, altering Sm valence from 2+ to 3+.
• This valence change leads to a substantial increase in carrier concentration.
• A record peak power factor of ~1.65 mW m⁻² K⁻² was achieved at 1023 K for Y-doped SmS.

Conclusions:

• Local chemical pressure is an effective strategy for tuning carrier concentration in mixed valence compounds.
• Y doping in SmS offers a highly efficient method for enhancing thermoelectric properties.
• This work provides new insights for designing high-performance thermoelectric materials containing mixed valence elements.