Fabrication of thermoelectric circuits by joining metallic microwires and the effect of the length of the wire on the thermoelectromotive force

The thermoelectromotive force due to the Seebeck effect is governed by the Seebeck coefficient of the thermoelectric circuit and the temperature gradient in the circuit. Thus for enhancing the thermoelectromotive force, not only selecting the materials but also inducing a large temperature gradient in a small space is very important in order to realize an efficient space-saving thermoelectric device. This paper describes a method by which the thermoelectric circuits can be fabricated by joining metallic microwires with Joule heat. Minor metal-free, Fe and Al microwires with diameters of 100μm and various lengths were used in the circuits, and the effect of the wire length on the thermoelectromotive force developed in the circuit was investigated. We observed the Seebeck effect in the circuit by controlling the temperature gradient in the circuit. It was found that the temperature at each end of the microwire depended on the temperature at the high temperature end and the wire length. We describe this phenomenon with a heat conduction model and analyze the dependency of the temperature gradient on the wire length. Finally, we were able to estimate the suitable length of the microwires for getting the largest thermoelectromotive force in the smallest possible space.