AbstractThe thermo e.m.f. of Zn, Ga, In, Sn, and Bi doped (1 and 1.5 wt%) Bi, Te, and Se is investigated over a large temperature range using solid as well as liquid samples (for Se the amorphous state is also included). The dopants Zn, Ga, In, and Sn strongly affect the thermo e.m.f. of solid but not of liquid Bi. Liquid Te and Se are found to show semiconductor properties determined strongly by impurities, especially for Se. The change in the sign of the thermo e.m.f. of liquid Se is explained by the existence of oxygen atoms acting as acceptors.