Relaxor Ferroelectricity Enables Enhanced Thermoelectric Performance in In₂Se₃-Alloyed GeTe

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Combining ferroelectric and thermoelectric materials presents challenges due to conflicting electrical conductivity needs.
• Germanium telluride (GeTe), a narrow-band-gap semiconductor with ferroelectric properties, is a key material for studying ferroelectricity-thermoelectricity interplay.

Purpose of the Study:

• To investigate novel strategies for optimizing electrical and thermal transport properties in thermoelectric materials.
• To explore the impact of germanium vacancies on the ferroelectric and thermoelectric characteristics of GeTe.

Main Methods:

• A non-equimolar (2:3) In3+/Se2- alloying strategy was employed to introduce germanium vacancies in GeTe.
• The electrical neutrality condition was maintained while inducing germanium vacancies.
• The thermoelectric figure of merit (zT) was evaluated for (GeTe)1-2x(In2Se3)x samples (x = 0.02-0.04).

Main Results:

• Germanium vacancies effectively induced relaxor ferroelectricity in GeTe, broadening the temperature range of minimum thermal conductivity.
• Ge vacancies stabilized the cubic phase of GeTe, leading to optimized electrical transport over an extended temperature range.
• An optimized average zT value exceeding 1.0 was achieved within the temperature range of 330-625 K.

Conclusions:

• The introduction of germanium vacancies via In2Se3 alloying is a viable strategy to synergistically enhance thermoelectric properties of GeTe.
• This approach successfully balances electrical and thermal transport properties, demonstrating potential for efficient thermoelectric materials.