Effects of silicon addition on thermoelectric properties of bulk Zn_4Sb_3 at low-temperatures

摘要

The thermoelectric properties of Si-doped compounds (Zn_(1-x)Si_x)_4Sb_3 (x= 0, 0.0025, 0.005, 0.01) have been studied. The results indicate that low-temperature (T < 300 K) thermal conductivity of moderately doped (Zn_(0.9975)Si_(0.0025))_4Sb_3 reduces remarkably as compared with that of Zn_4Sb_3 due to enhanced impurity (dopant) scattering of phonons. Electrical resistivity and Seebeck coefficient are found to increase and then decrease moderately with the increase in the Si content. In addition, first-principles calculations are performed on the occupation options of Si atoms in disordered β-Zn_4Sb_3. The results indicate that Si atoms occupy preferentially the Zn vacancies in normal sites. Subsequently, Si atoms will substitute for interstitial Zn atoms. The lightly doped compound (Zn_(0.9975)Si_(0.0025))_4Sb_3 exhibits the best thermoelectric performance due to the improvement in both its thermal conductivity and Seebeck coefficient. Its figure of merit, ZT, is about 1.3 times larger than that of pure Zn_4Sb_3 at 300 K.