Investigations on Cuprous Selenide and Copper Tellurides

Abstract

The activity of copper in cuprous selenide and various phases of the system copper-tellurium as a function of the metal-to-nonmetal ratio has been determined with the help of coulometric titrations. At 400°C the homogeneity range of cuprous selenide extends from a Cu/Se ratio of 1.9975±0.001 to a value lower than 1.86. Homogeneous phases of the system Cu–Te have been found between Cu/Te ratios equal to about 2 to 1.92, 1.43 to 1.39, and 1.32 to 1.30.

Ionic conductivity and chemical diffusion in LixCu2−xSe superionic alloys

“…Figure 1 shows the temperature dependence of the ionic conductivity (Yi for the high temperature a-phases of Ln(oiT),S/cm Values of ~i for pure CuzSe (x=0) agree well with literature data [6][7][8]. Figure 1 shows the temperature dependence of the ionic conductivity (Yi for the high temperature a-phases of Ln(oiT),S/cm Values of ~i for pure CuzSe (x=0) agree well with literature data [6][7][8].…”

“…The high temperature cubic m-phase of copper selenide has the Fm3m crystal lattice [5] and it is a superionic conductor for Cu + ions with extremely high values of the ionic conductivity (= 2 S/cm at 623 K) [6][7][8]). By electrochemical insertion of lithium into nonstoichiometric Cu2_xS (0< x<0.25) LiyCu2_x S solid solutions are formed, where 0<y_<0.25 [9].…”

Superior intrinsic thermoelectric performance with zT of 1.8 in single-crystal and melt-quenched highly dense Cu2-xSe bulks

“…The exact congruent melting composition for Cu 2- x Se, has been reported to be Cu 1.9975 Se36, or Cu 1.9956 Se37, or Cu 1.994 Se38. For Cu 2- x Se with other x values, the melting should not be congruent, and the chemical compositions of melt-quenched samples should be different from the nominal compositions of the starting materials.…”

Solid‐State Ionics: Roots, Status, and Future Prospects

“…The high-temperature phases present a disordered structure similar to that observed in the halides, but the bandgap is much lower, so that both compounds are mixed ionic-electronic conductors with a large, almost metallike, total conductivity. Copper chalcogenides usually present a cation deficit (Cu 2Ϫ␦ X, where X ϭ S, Se, and Te) 30,31,134 and p-type conductivity, whereas silver chalcogenides tend to metal excess (Ag 2ϩ␦ X) and exhibit n-type conductivity. Copper chalcogenides were used as electrode materials in early silver and copper batteries and for fundamental thermodynamic and kinetic investigations during the 1950s, 29,30 so that transport characteristics of electrons, holes, and ions were thoroughly determined from polarization and relaxation processes.…”