Thermoelectric technology converts waste heat into electricity, a capability expected to support carbon-neutral development. However, materials must simultaneously achieve high electrical performance and low thermal conductivity—requirements that conflict in conventional designs.

Embedding atomically thin materials within bulk crystals

Researchers at Institute of Science Tokyo developed TlFe1.6Se2, a layered crystal embedding atomically thin iron selenide (FeSe) layers within bulk material alongside ordered Fe vacancies. This design combines the exceptional thermoelectric power factor of ultrathin FeSe with significantly reduced thermal conductivity.

The crystal demonstrates two critical advantages. First, embedded FeSe atomic layers produce substantially higher thermoelectric power factors than conventional bulk FeSe, primarily through enhanced Seebeck coefficients. Second, naturally occurring Fe vacancies distort atomic bonds and scatter heat-carrying phonons, drastically reducing thermal conductivity to approximately 0.2 W m⁻¹ K⁻¹.

At approximately 180°C, the material undergoes reversible transition between Fe-vacancy-ordered and disordered phases, further enhancing phonon scattering. In the ordered phase, the Seebeck coefficient exceeds 100 μV K⁻¹, yielding a thermoelectric power factor approximately five times larger than that of the disordered phase.

Professor Takayoshi Katase noted: “This work demonstrates the effectiveness of a new design concept in which the functionality of low-dimensional materials is embedded within bulk crystals.”

Journal: Journal of Materials Chemistry A
DOI: 10.1039/D6TA02075E
Article Title: Simultaneous enhancement of power factor and suppression of thermal conductivity in bulk TlFe1.6Se2 via embedded atomically thin FeSe layers
Publication Date: June 23, 2026

Source: EurekAlert