Electronic and Ionic Conduction in Cu_2-δSe, Cu_2-δS and Cu_2-δ(Se, S)

Abstract

Using the galvanic cell Cu|CuBr·C 6 H 12 N 4 CH 3 Br|Cu 2-δ VI|Pt, the deviation δ from the stoichiometric composition is varied up to 0.2 for Cu 2-δ Se, Cu 2-δ S and their alloys. Electronic conductivity, thermoelectric power and Hall coefficient are measured as functions of e.m.f. of the cell, E , and of temperature, T , (20°C∼200°C). The phase diagrams are constructed front these results, especially from E vs T plots, and the electrical properties arc interpreted by the use of a simple model. Further, the ionic conductivity is measured with the use of the cell in low temperature phase as well as in high temperature one. The value of E seems not to represent the Fermi kinetic energy even in the high temperature phase having the average structure. This is because of the largeness of δ, and can be interpreted as being due to the screening effect of carriers (holes) on copper ion vacancies.