[15a-E206-1~12] 9.4 Thermoelectric conversion

△ [15a-E206-10] Thermoelectric properties of Sn₂S₃ with electron lone pairs

〇(M1)Wataru Saito¹, Kei Hayashi¹, Hiroki Nagai¹, Yuzuru Miyazaki¹ (1.Tohoku Univ.)

Keywords:thermoelectric materials, electron lone pairs

In this report, we focused on Sn₂S₃, which is a mixed Sn valence compound leading to generate electron lone pairs in the crystal. Since Sn₂S₃ units are weakly bonded via the electron lone pairs, a satisfactorily low thermal conductivity can be expected. In fact, the thermal conductivity as low as ~ 1.0 W/mK was realized from 400 K to 700 K. Although the absolute value of Seebeck coefficient was high (> 300 μV/K), the electrical conductivity was significantly low (~ 0.1 S/cm at 700 K). As a result, the highest ZT was as low as 1.0 × 10^-3 at 700 K. From the band gap measurements and calculation of Seebeck coefficient, it is believed that Sn₂S₃ is intrinsic semiconductor with the energy gap of E_g = 1.2 eV, which causes the low electrical conductivity. Partials substitution of Sn site is needed to increase electrical conductivity.