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New energy from rare earth

New energy from rare earth

A team of scientists has discovered a novel approach to crafting higher thermoelectric efficiencies, which can help develop electrical energy from waste heat such as that emitted by internal combustion engines. Professor André Strydom from the Department of Physics at the University of Johannesburg (UJ) collaborated with researchers from the Chinese Academy of Sciences in Beijing; Institute of Solid State Physics in Vienna; the Max Planck Institute in Dresden; and the University of Aarhus in Denmark in the discovery.

A research article, Large Seebeck Effect by Charge-Mobility Engineering, co-authored by Prof Strydom, appeared in the June 2015 edition of Nature Communications.

“The Seebeck effect has in recent years found its way into everyday life. Refrigerators having no electric motor or compressor and no moving parts have already started becoming available commercially. There are also sustainable cooling technologies such as in portable cooling boxes,” he says.

“The Seebeck effect is a remarkable phenomenon which describes the generation of an electric potential in a conducting material when exposed to a temperature gradient. Equally fascinating is the reverse effect, namely the spontaneous cooling down that one end of a thermoelectric material experiences when an electric potential is applied across its two end points.”

Clearly it is worth developing ever-more efficient cooling technologies. However, turning waste heat into electrical energy is an equally compelling challenge for scientists, Prof Strydom says.

“As an example, motor vehicles in cities across the planet expel copious amounts of waste heat from their internal combustion engines. That heat can be useful if it is turned into electricity.”

In the authors’ work to understand certain unusual features in their fundamental studies of strongly correlated electron systems, they stumbled upon an obscure relation between the mobility of charge carriers in a metal, and its Seebeck effect. It is this relation that paves the way for a new route to develop electrical energy from sources such as waste heat from vehicle engines.

The subject of the main part of the article deals with carefully synthesized Ni-doped CoSb3. Through collaboration with Prof Strydom’s research group, an intriguing connection was established with a ternary rare-earth compound (CeRu2Al10), which has been at the focus of a research project of his in the Physics Department of the University of Johannesburg since 2009. This connection was a key factor to prove the principle behind their discovery to be ubiquitous in various types of materials.

Prof Strydom has held the position of Visiting Professor at the Chinese Academy of Sciences in Beijing since 2012, where he has been hosted for a number of research visits to date.

Pictured: Prof André M Strydom from the Department of Physics at the University of Johannesburg (UJ)