Product and Thermoelectric Properties of Thermoelectric Materials with Mesoscopic Structure

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We can have two important results in this research. The first is the observation of non-equilibrium stationary state between the electron and lattice systems in thermoelectric materials. Typical thermoelectric phenomenon, The Peltier effect is incarnated by only the electron system and the lattice system is warmed up through the thermal interaction between both systems. The electrons are coercively carried by the applied electric field. Furthermore, the Peltier heat is continuously reproduced during the impression of dc current. Therefore, non-equilibrium stationary state could appear between the electron and lattice systems. We tried to measure the electron and lattice temperatures, using the developed equipment in this grant and could confirm that the non-equilibrium phenomenon between the electron and lattice systems was surely caused by the Peltier effect. The second is improvement of the figure of merit in the Bi micro-wire array. The figure of merit is strongly enhanced to be ZT=0.287 in the micro-wire array. The obtained value is approximately 2.8 times larger than that (ZT=0.1) in the Bi bulk device. Furthermore, we could explain that the origin came from the control of the crystal axis in the array, examining the measured values of the other thermoelectric physical quantities. In this grant we developed the evaluation equipment by the Harman method and some important results such as the non-equilibrium stationary state between the electron and lattice systems and the improvement of the figure of merit in the Bi micro-wire array.