Electrical Transport and Thermoelectric Properties of SnSe-SnTe Solid Solution

Area of Science:

• Materials Science
• Solid-State Physics
• Thermoelectric Materials

Background:

• Single crystal tin selenide (SnSe) shows excellent thermoelectric (TE) performance but is impractical for applications due to poor mechanical properties and high fabrication costs.
• Polycrystalline SnSe TE properties are significantly lower than single crystals, necessitating improvements for practical use.

Purpose of the Study:

• To enhance the thermoelectric properties of polycrystalline SnSe by fabricating SnSe-SnTe solid solutions.
• To investigate the effects of Te doping on the electrical transport and TE properties of SnSe.

Main Methods:

• Fabrication of polycrystalline SnSe$_{1-x}$Te$_{x}$ solid solutions using mechanical alloying and spark plasma sintering.
• Analysis of material structure using X-ray diffraction (XRD).
• Evaluation of electrical transport and thermoelectric properties, including figure of merit (ZT).

Main Results:

• The solubility limit of Te in SnSe was determined to be between x = 0.3 and 0.5.
• Increasing Te content enhanced electrical conductivity due to higher carrier concentration.
• Lattice thermal conductivity was reduced by phonon scattering from point defects, leading to improved TE performance.

Conclusions:

• SnSe-SnTe solid solutions offer a viable route to improve the thermoelectric properties of polycrystalline SnSe.
• A figure of merit (ZT) of approximately 0.78 was achieved at 823 K for SnSe$_{0.7}$Te$_{0.3}$, representing an 11% improvement over SnSe.
• The study demonstrates the potential of controlled alloying for optimizing thermoelectric materials.