Thermoelectric materials and transport physics

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Thermoelectrics for medical applications: Progress, Challenges, and Perspectives

Additive Manufacturing of Thermoelectrics: Emerging Trends and Outlook

Flexible Elemental Thermoelectrics with Ultra-high Power Density

Cold-Sintered Bi2Te3-Based Materials for Engineering Nanograined Thermoelectrics

GeTe is among the best medium-temperature thermoelectrics. Its high performance originates from band convergence at the phase transition and low lattice thermal conductivity due to Peierls distortion. In most studies, the peak performance (zT) in GeTe is achieved by designing and optimizing its electronic and thermal transport properties near its phase transition temperature (700 K). However, for efficient power harvesting, a high average zT (zTave) across a wide temperature range is desirable. This calls for a holistic performance evaluation and enhancement not only near 700 K, but also at room temperature. In this work, we leveraged on the confluence of performance enhancement strategies via Cu2Te alloying and In resonant doping to achieve a record-high room temperature power factor of 2800 μW mK−2, and an average power factor of 3700 μW mK−2 between 323 and 773 K. The magnitude of the room temperature power factor is comparable to that of the state-of-the-art Bi2Te3 based compounds. In the optimized sample with Bi doping, a room temperature zT of 0.5 is achieved, highest for lead-free GeTe. Ultimately, a high peak zT of 2.1 at 723 K and single leg power conversion efficiency of 11.8% were achieved between 323 and 745 K, which are among the highest reported for lead-free GeTe.

Suppressing Ge-vacancies to achieve high single-leg efficiency in GeTe with an ultra-high room temperature power factor

The key to designing a Half-Heusler begins from the understanding of atomic interactions within the compound. However, this pool of knowledge in Half-Heusler compounds is briefly segregated in many papers for specific explanations. The nature of the chemical bonding has been systematically explored for the large transition-metal branch of the half-Heusler family using density-of-states, charge-density, charge transfer, electron-localization-function, and crystal-orbital-Hamilton-population plots. This review aims to simplify the study of conventional 18-electron configuration Half-Heusler by applying rules proposed by renowned scientists to explain concepts such as Zintl-Klemm, hybridization and valence electron content (VEC). Atomic and Molecular orbital diagrams illustrate the electron orbital transitions and provides clarity to the semiconducting behavior (VEC=18) of Half-Heusler. 18-electron Half-Heusler usually exhibits good thermoelectric properties owing to favorable electronic structures such as narrow band gap (<1.1eV), thermal stability and robust mechanical properties. The insights derived from this review can be used to design high performance Half-Heusler thermoelectrics.

Solco Samantha Faye Duran

Papers

Suppressing Ge-vacancies to achieve high single-leg efficiency in GeTe with an ultra-high room temperature power factor

A Systematic Approach for Semiconductor Half-Heusler

Physical Intuition to Improve Electronic Properties of Thermoelectrics