Spin Seebeck thermoelectric device improves efficiency

Thermoelectric conversion technology that converts energy abandoned as waste heat back to electric power is strongly anticipated to be used for saving energy and reducing greenhouse gas emissions. Although conventional spin Seebeck thermoelectric devices have the advantages of a low manufacturing cost and high versatility and durability, their energy conversion efficiency is inferior.

“We have improved the conversion efficiency of this spin Seebeck thermoelectric device by more than ten times because of its newly developed material and device structure,” said Soichi Tsumura, General Manager, IoT Device Research Laboratories, NEC Corporation. “Furthermore, devices made of flexible material, such as resin, have been achieved using a manufacturing process that does not require high temperature heat treatment.”

“The conversion efficiency of this new spin thermoelectric device has been improved by almost one million times when compared to the earliest device, and has taken an important step towards practical use as a generator element. The achievement of practical use as a heat flux sensor is also in sight.”

In the future, the three parties participating in this development aim to further the research and development of technologies to generate electricity from the large amount of waste heat emitted by plants, data centres, vehicles and others.

Key features of this new technology are as follows

1. Development of a low cost, high performance ferromagnetic alloy and significant improvement in thermoelectric conversion efficiency.

Conventionally, expensive platinum was used as the electrode material to extract electric power in a spin Seebeck thermoelectric device. This time, new cobalt alloys were developed to replace the platinum. As a result, the cost was significantly reduced. Furthermore, the combination of the thermoelectric effect termed the ‘Anomalous Nernst Effect’ appearing due to the ferromagnetic properties added to the cobalt alloys and the spin Seebeck effect, have improved the thermoelectric conversion efficiency by more than ten times.

2. Devices with bending resistance and low heat treatment temperature achieved by new deposition technology.

New deposition technology fabricates a fine ferrite film for spin Seebeck thermoelectric devices at 90°C, much lower than the 700°C used with the conventional method. Owing to the decrease in heat treatment temperature, elements can be created on the surface of plastic film etc, and flexible devices of various shapes are created.