Atomic-scale engineering improves thermoelectric materials for harvesting waste heat
Latest results now published in the journal Science Advances
At a glance:
- Challenge: Thermoelectric materials can turn waste heat into electricity. However, their widespread use is limited by high costs and dependence on critical elements. Thus far, earth-abundant thermoelectric materials either suffer from a lower conversion efficiency or a limited lifetime.
- Research question: To address the limited lifetime of thermoelectric materials, metal ion migration needs to be inhibited, which otherwise triggers decomposition and a rapid loss of performance. How to control this metal ion migration and make thermoelectric materials more durable?
- Results: Researchers show that powder atomic layer deposition can suppress ion migration, significantly improving the material's stability.
- Outlook: The approach could be further developed by designing atomic layer deposition stacks that not only prevent ion migration but also enhance electrical conductivity, paving the way for longer-lasting, high-performance thermoelectric materials.
Every day, enormous amounts of energy are lost as waste heat from car engines to data centres and household appliances. Thermoelectric materials offer a way to capture some of this lost energy by converting heat directly into electricity. They could make industrial processes more energy-efficient, extend the lifetime of battery-powered sensors and provide environmentally friendly cooling technologies.
However, turning this potential into practical technologies remains challenging. Efficient thermoelectric materials must allow electrical current to flow easily while preventing heat from escaping. Their widespread use is still limited due to their high costs and dependence on critical elements such as Tellurium. Thus far, earth-abundant thermoelectric materials have either a lower conversion efficiency or limited lifetime.
Researchers at the Max Planck Institute for Sustainable Materials (MPI-SusMat) have contributed to a study led by the Leibniz Institute for Solid State and Materials Research (Dresden) and the Technical University Dresden that improves the material’s stability through supressing metal ion migration – the main cause for decomposition and a rapid performance loss in thermoelectric materials. They published their findings in the journal Science Advances.
Atomic barriers supress metal ion migration
The researchers focussed on a special class of thermoelectric materials, so-called phonon-liquid electron-crystal materials. “This special thermoelectric material class allows electrons to move freely leading to a high electrical conductivity, while heat is poorly conducted - exactly what we need for turning waste heat into electricity”, says Dominique Mattlat, PhD researcher at MPI-SusMat and co-author of the publication. The team used a zinc-antinomy alloy (β-Zn4Sb3) as a model system.
“Our collaborators from the Leibniz Institute for Solid State Research produced atomic-scale interfaces of zinc oxides using powder atomic layer deposition. These interfaces act as barriers that keep zinc ions in place and thus prevent phase decomposition that leads to a rapid performance loss”, explains Dr Siyuan Zhang, project group leader at MPI-SusMat and co-author. Creating an ultra-thin barrier that blocks the movement of metal ions without compromising the material's ability to convert heat into electricity has been a major challenge. Such barriers must be continuous and only a few nanometres thick to work effectively.
The MPI-SusMat team contributed to the study with advanced electron microscopy techniques to characterize the materials. The researchers were able to identify these thin zinc-oxide barriers, proving their successful deposition to block the zinc ion migration. Moreover, they discovered that the zinc-oxide barriers act like a "cage" to limit grain growth and produce a fine-grained structure. Importantly, the smaller grains help lower the thermal conductivity and maintain a high energy conversion efficiency. As a result, introducing zinc-oxide barriers enables simultaneous improvement in the device performance and the stability during operation at high temperatures.
Next step: barrier stacks
The findings demonstrate that powder atomic layer deposition can be used to control interfaces in thermoelectric materials and ion-electron conductors. The researchers now aim to design atomic layer deposition stacks that combine stronger ion blocking with enhanced charge carrier mobility, paving the way for more durable thermoelectric materials with superior conversion efficiency.
Original publication
Author: Yasmin Ahmed Salem
