Thomson effect transforms FeRh-based alloys into thermoelectric materials
Thomson effect transforms FeRh-based alloys into thermoelectric materials lead image
As thermoelectric fundamentals, the Seebeck and Peltier effects are often exploited in thermal energy harvesting and solid-state heat pumps. However, the devices based on these principles require multiple-junction structures, which complicate design and limit applications.
When a charge current and a temperature gradient are applied to a conductor, the Thomson effect induces heat release or absorption proportional to the gradients. Using the Thomson effect instead of the Peltier effect may enable thermoelectric cooling with a single material, but this technique has so far not been applied because of its small thermoelectric conversion performance and measurement difficulty.
Modak et al. measured the giant Thomson effect across the antiferromagnetic-ferromagnetic phase transition in FeRh-based alloys. While not directly connected to practical applications, the alloys show the potential of the Thomson effect and provide new opportunities for materials science and thermal engineering.
“We found that phase transition materials can exhibit giant Thomson coefficients even when their Seebeck coefficients are small,” said author Rajkumar Modak. “Thus, even substances that are not conventionally regarded as thermoelectric materials have a potential to be used for thermoelectric conversion based on the Thomson effect.”
The team used an active infrared emission microscopy called the lock-in thermography technique, which was useful for visualizing the temperature change induced by the thermoelectric effects, to demonstrate the cooling behavior due to the Thomson effect.
Although the researchers realized the direct observation of the giant Thomson effect, practical applications of the Thomson device require the evaluation of its cooling efficiency and device engineering.
“We are working to evaluate the coefficient of performance of the Thomson devices by developing a new formulism,” said author Ken-ichi Uchida.
Source: “Phase-transition-induced giant Thomson effect for thermoelectric cooling,” by Rajkumar Modak, Masayuki Murata, Dazhi Hou, Asuka Miura, Ryo Iguchi, Bin Xu, Rulei Guo, Junichiro Shiomi, Yuya Sakuraba, and Ken-ichi Uchida, Applied Physics Reviews (2022). The article can be accessed at https://doi.org/10.1063/5.0077497 .
