Electrochemical investigations of a copper-tellurium system and determination of the band gap for α-Cu2Te

Abstract The activity of copper in various phases of the copper—tellurium system as a function of the metal to nonmetal ratios has been determind with the help of solid-state coulometric titrations in the temperature region between 350 and 450°C. Homogenous phases of the CuTe system have been found between Cu/Te ratios equal to about 2 1.92 [α-phase (Cu 2 Te)], 1.43 1.39 [β-phase (Cu 4 Te 3 )] and 1.32 1.30 [γ-phase (CuTe)]. Analysis of the experimental data shows that the semiconducting properties of α-Cu 2 Te and the change of the thermodynamic quantities with composition are due to changes of the thermodynamic quantities of the electrons as a component. The change of the thermodynamic quantities of the electrons are composed of those of the free electrons and electron holes. From the electrochemical measurements, besides partial molar enthalpy curves of electrons, the energetic band gap can be calculated and is about 0.673 eV for α-cuprous telluride.