AbstractElectrical conductivity σ(T) and thermo-e.m.f. S(T) measurements were performed for ternary Cu-based chalcogenides in a wide temperature range. A concentration range of the semiconductor-metal transition has been determined. A radical alteration in the electron spectrum occurs in the region of x = 0.6-0.8, namely, a semiconductor-metal transition takes place. Complete metallization of alloys takes place with temperature increasing. Further heating is accompanied by electrical conductivity decreasing followed by final exponential electrical conductivity dependence with seeming negative activation energy, while thermopower increases without changing a sign. This process is accompanied by an increase of a free electrons concentration. At the same time, at higher temperatures when the alloy’s density decreases, localization of the wave functions of electrons on separated atoms or atoms groups caused by density fluctuations, occurs. For alloys with Se content, the electrical conductivity decreasing caused by thermal expansion, could be intensified at the expense of molecular units formation. A simultaneous density decreasing causes an appearance of small dynamic groups like Se
