Dramatically Enhanced Mechanical Properties of Nano-TiN-Dispersed n-Type Bismuth Telluride by Multi-Effect Modulation

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Bismuth telluride (Bi₂Te₃)-based alloys are crucial for thermoelectric energy harvesting and refrigeration.
• Commercial production via zone-melting (ZM) yields materials with poor mechanical properties, limiting device applications.
• N-type Bi₂Te₃ alloys are particularly prone to cracking, hindering their widespread use.

Purpose of the Study:

• To improve the mechanical properties of n-type Bi₂Te₂.₇Se₀.₃ alloys.
• To maintain excellent thermoelectric performance alongside enhanced mechanical strength.
• To explore the effects of grain refinement and titanium nitride (TiN) composite phase introduction.

Main Methods:

• Utilized a mixed mechanism of grain refinement and TiN nanoparticle addition.
• Introduced nano-TiN to create pinning effects and hinder crack propagation.
• Investigated nanoscale processes to modify material microstructure.

Main Results:

• Achieved significant enhancements in hardness (0.98 GPa, +181%), bending strength (36.3 MPa, +60%), and compressive strength (74 MPa, +67%) compared to ZM ingots.
• Maintained identical thermoelectric performance, with a peak dimensionless figure of merit (ZT) of 0.957 at 375 K.
• Demonstrated a ZT value of 0.89 across the 325-450 K temperature range.

Conclusions:

• The TiN-dispersed Bi₂Te₂.₇Se₀.₃ alloys exhibit superior mechanical properties while retaining high thermoelectric efficiency.
• This approach significantly increases the reliability and application scope of bismuth telluride devices.
• The multi-effect strategy for mechanical property enhancement is applicable to other thermoelectric material systems.