This review briefly discusses the relationship between crystal structures, electronic structures, and thermoelectric properties of target materials. Examples include pseudogap quasicrystals and related approximant crystals, narrow-gap binary intermetallic compounds, and lead chalcogenides. The approach used is to identify the intrinsic physical properties from the experiment and establish a route for tuning their properties based on theoretical models and first-principles calculations. A possible route for improved thermoelectric performance is to use a band engineering approach, such as band convergence and introducing impurity states near the valence and conduction band edges. This approach was successfully applied to TiSi₂-type RuGa₂ and lead chalcogenides PbTe and PbSe.

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We demonstrated the thermoelectric power generation system utilizing exhaust heat from generators. In this system, gas flow is disturbed, so the alternately arranged pin fins with high thermal conductivity were adopted as heat exchangers. Furthermore, the exhaust heat power generation data was measured and compared with the simulation model of the fuel cell system. As a result, in the 700 W class fuel cell, the measured data agreed well with the simulation model results, and it was found that 2.8 W power generation energy was obtained. Also, in the 10 kW class generator with four thermoelectric power generation units in tandem, 268.4 W power generation energy was estimated.

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Thermoelectric properties of Sc-doped β-rhombohedral boron were examined in the temperature range of 373 K to 973 K. The electrical conductivity increased drastically by Sc doping. Positive Seebeck coefficient decreased because of an increase in the carrier concentration. In addition, the power factor enhanced from 0.013 μWm^－1K^－2 to 10 μWm^－1K^－2 at 673 K. The thermal conductivity reached the theoretical minimum lattice thermal conductivity of 2.3 Wm^－1K^－1 at 473 K by Sc doping. The maximum ZT value enhanced from 0.006 to 0.020 at 973 K for Sc_2.0B₁₀₅ as a p-type thermoelectric material.

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