Electronic and Ionic Conduction in (Ag_xCu_1−x)₂Se

Abstract

The phase diagram is studied by X-ray and thermal analyses. The high temperature phase (α) is the solid solution of b.c.c. or f.c.c. in which Ag⁺, Cu⁺ and electron are mobile. The galvanic cell Ag|AgI|specimen|Pt is available to controle the excess or deficit Ag density and to detect the electrochemical potential of Ag⁺, since the interdiffusion of Cu⁺ into AgI is nearly forbidden except near Cu₂Se. With the help of the cell and utilizing the weight-difference between Ag and Cu, the polarization and the interdiffusion are measured and interpreted with the diffusion theory. The electronic and ionic conductivities are measured with varying temperature and x. Further the various properties of α(Ag, Cu)₂Se such as the conductivity, Hall coefficient, thermoelectric power, thermal conductivity etc. are measured and compared with the theory, indicating that the energy gap decreases with increasing x.