Ionic Conductivity in Liquid Sn-Se, Sb-Se and Bi-Se Alloys

抄録

Simultaneous measurements of ionic and electronic conductivities around the stoichiometric composition have been carried out on liquid Sn–Se, Sb–Se and Bi–Se alloys by applying the residual potential theory. The ionic conductivity, σ_i, in liquid Sn–Se and Sb–Se alloys increases with increasing temperature, while, in liquid Bi–Se alloys, it decreases with increasing temperature. The isothermal σ_i in liquid Sn–Se and Sb–Se alloys at higher temperatures exhibits a minimum at the stoichiometric composition of SnSe and Sb₂Se₃, respectively, and, on the other hand, it shows a maximum at Bi₂Se₃ in liquid Bi–Se alloys. Values of σ_i at SnSe, Sb₂Se₃ and Bi₂Se₃ near the melting temperature are 7.40 Sm⁻¹ at 1173 K, 0.448 Sm⁻¹ at 893 K and 45.3 Sm⁻¹ at 993 K, respectively, which are about two orders of magnitude smaller than the corresponding electronic conductivities, σ_e. The value of σ_i of liquid Bi₂Se₃, which is the largest among three liquids, is roughly comparable to that for ionic liquid alloys such as Ag and Tl-chalcogenides. In contrast, liquid Sb₂Se₃ indicates the smallest σ_i due to the strong covalent bonding between unlike atoms. The minimum of the σ_i-isotherm at SnSe and Sb₂Se₃ in liquid Sn–Se and Sb–Se alloys also reflect the covalent nature in these liquids.