Tellurium-free Thermoelectric Technology for Near-room-temperature Applications

Project Information

TENTATION

Grant agreement ID: 101116340

DOI

10.3030/101116340

EC signature date 4 October 2023

Start date 1 January 2024

End date 31 December 2028

Funded under

• European Research Council (ERC)

Total cost

€ 1 498 895,00

EU contribution

€ 1 498 895,00

Coordinated by

LEIBNIZ INSTITUT FUR FESTKORPER UND WERKSTOFFORSCHUNG DRESDEN EV
Germany

Periodic Reporting for period 1 - TENTATION (Tellurium-free Thermoelectric Technology for Near-room-temperature Applications)

Reporting period: 2024-01-01 to 2026-06-30

Summary of the context and overall objectives of the project

Thermoelectric (TE) technology offers a unique way to manage heat and generate electricity without moving parts or traditional refrigerants. Using the Seebeck and Peltier effects, TE devices can convert low-grade waste heat directly into electrical power or provide precise cooling. Their solid-state design makes them reliable, compact, and suitable for applications ranging from industrial heat recovery to powering remote sensors and cooling sensitive electronics.

Despite this potential, commercial near-room-temperature thermoelectrics are currently restricted by a fundamental materials bottleneck. Prevailing technologies rely almost exclusively on bismuth telluride (Bi2Te3) alloys. Tellurium is among the rarest stable elements in the Earth’s crust (<0.001 ppm), with a global annual production of less than 500 tons. This scarcity, exacerbated by toxicity, renders Bi2Te3-based solutions economically and environmentally unsustainable for large-scale deployment. Furthermore, current commercial modules exhibit modest conversion efficiencies (~3-6%), underscoring the need for materials with both superior dimensionless figures of merit (zT) and higher elemental abundance.

This project addresses this dual challenge by developing a new generation of tellurium-free TE materials and modules based on magnesium-based compounds. Magnesium offers a compelling alternative due to its high crustal abundance, low density, and benign environmental profile. By optimizing Mg-based architectures for both n-type and p-type legs, the research aims to surpass traditional performance limits through precise control of carrier concentration and phonon scattering mechanisms. The technical approach integrates advanced synthesis protocols, microstructural refinement, and sophisticated contact engineering to mitigate parasitic losses at the device level.

The expected impact of this research is a transformative shift in the thermoelectric landscape. Magnesium-based modules would offer a sustainable, higher-performance alternative to current devices, enabling broader use in energy harvesting and thermal management applications, from recovering waste heat in factories to cooling next-generation electronics, without relying on scarce or toxic elements.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the reporting period, the project addressed the key limitations that have historically restricted the performance of magnesium-based thermoelectric materials.

A central challenge was the loss of magnesium during high-temperature processing. Magnesium evaporation creates lattice defects that severely degrade electrical performance. To overcome this, we developed a novel “lattice-healing” strategy that introduces small amounts of stabilizing elements (e.g. calcium) to compensate for magnesium loss and suppress defect formation. This approach significantly improved structural integrity and enabled Mg-based compounds to reach advanced thermoelectric efficiencies.

To further control magnesium evaporation, we designed a “quasi-closed” sintering process. This tailored thermal treatment minimizes Mg loss during densification and promotes the growth of larger, more uniform grains, thereby enhancing electrical conductivity. In parallel, a high-purity synthesis route was established to reduce oxygen contamination, which otherwise deteriorates transport properties. Together, these processing innovations substantially improved material quality and reproducibility.

At the device level, we engineered a new low-loss electrical interface layer between the Mg-based thermoelectric legs and metallic interconnects. This interface reduces contact resistance, strengthens mechanical bonding, and suppresses parasitic chemical reactions during operation.

To ensure long-term environmental stability, an ultra-thin HfO2 protective coating was deposited via atomic layer deposition (ALD). Despite being only a few hundred atomic layers thick, this coating effectively blocks the ingress of moisture and oxygen. As a result, the modules demonstrated exceptional durability, maintaining stable performance over more than 65,000 thermal cycles.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The TENTATION project has achieved breakthroughs that move thermoelectric technology well beyond the long-standing benchmark established by tellurium-based systems such as bismuth telluride.

For decades, state-of-the-art thermoelectric devices have relied on bismuth telluride, which depends on the extremely scarce element tellurium and has shown only incremental efficiency gains. In contrast, our work demonstrates that magnesium-based, tellurium-free materials can not only eliminate reliance on scarce elements but also deliver competitive or superior performance.

The lattice-healing concept represents a fundamental advance in defect management for volatile-element systems, enabling Mg-based materials to achieve performance levels previously considered unattainable. This establishes them as a realistic and sustainable alternative to conventional tellurium-containing compounds.

The quasi-closed sintering approach further advances the field by offering a scalable manufacturing pathway that maintains compositional stability during high-temperature processing—an issue that has historically limited Mg-based systems. Importantly, this method is compatible with industrial production.

At the module level, the combination of low-resistance electrical contacts and conformal ALD protection enabled efficiencies exceeding those of many commercial systems based on traditional materials, while simultaneously achieving unprecedented cycling stability for Mg-based devices. The demonstrated long-term durability under repeated heating and cooling represents a step change in reliability for this material class.

Together, these results shift magnesium-based thermoelectrics from a laboratory curiosity to a technologically viable platform for sustainable waste-heat recovery and solid-state cooling, significantly extending the frontier of thermoelectric materials research.