Thanks to new materials and a new device structure, the Japanese researchers claim a conversion efficiency more than 10 times higher than prior art relying on the spin Seebeck thermoelectric effect.
Published in Scientific Reports under the title “Flexible heat-flow sensing sheets based on the longitudinal spin Seebeck effect using one-dimensional spin-current conducting films”, the paper discloses a ferrite plating method, growing a 1μm-thick Ni0.2Zn0.3Fe2.5O4 ferromagnetic film on a 25μm-thick polyimide substrate at a process temperature of 90°C.
Not only the process is achieved at much lower temperatures than competing solutions (they mention 700°C for conventional methods), but they rely on an aqueous reaction of two solutions, (FeCl2 + NiCl2 + ZnCl2) and an oxidizer (NaNO2 + CH3COONH4) spread on a plastic film through two nozzles, making the process relatively easy to scale up on large sheets of plastic films or even across various shapes.
The paper described how the thin-film TE could be successfully used as a heat-flow sensor for pervasive and large-scale monitoring, but in the future, the three parties participating in this development aim to further improve energy conversion yields to be able to generate electricity from the large amount of waste heat emitted by plants, data centres, vehicles and other heat sources.
The researchers also boast that they were able to replace the expensive platinum typically used as the electrode material to extract electric power in spin Seebeck thermoelectric devices, by new cobalt alloys, significantly reducing production costs.
These results were achieved as part of the Exploratory Research for Advanced Technology (ERATO) “SAITOH Spin Quantum Rectification Project” of the Japan Science and Technology Agency (JST), running from 2014 to 2020 under the direction of Eiji Saitoh, Professor of Tohoku University. Note that Saitoh and Associate Prof. Ken-ichi Uchida of Tohoku University were the discoverers of the Spin Seebeck thermoelectric effect in 2008.
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