Cu Diffusion and Ionic Conduction

The first 64Cu tracer measurements of ionic diffusion were reported for various Cu-rich compositions in these glass systems. In agreement with previous alternating-current impedance results, and Wagner direct-current polarization measurements, it was found that pure Cu+ ion-conducting glasses (CuI-33As2Se3-17PbI2, CuI-20PbI2-10SbI3-20As2Se3) exhibited the highest Cu tracer diffusion coefficients and lowest activation energies for diffusion. The room-temperature Cu diffusivities were higher, by between 4.5 and 5.5 orders of magnitude, than those in an As2Se3 glass. The Haven ratio was found to be between 0.52 and 0.61 (ternary glass) or between 0.93 and 1.00 (quaternary glass). Short-range diffusional displacements of I ions, that were induced by hopping CuI ions, were also detected in the CuI-PbI2-SbI3-As2Se3 glass system by means of Mössbauer spectroscopy at temperatures ranging from 4.2 to 305K. It was noted that the activation energy for local hopping (about 0.31eV) was very similar to that for bulk ionic conduction (0.37eV) or for Cu diffusion (about 0.33eV). When compared to the CuI-based vitreous alloys, a 50:50 Cu2Se•As2Se3 glass exhibited Cu diffusivities which were 2 to 5 orders of magnitude lower, while the Cu-ion transport number was between 0.0001 and 0.001 at temperatures ranging from 140 to 170C.

E.Bychkov, A.Bolotov, J.Grushko, J.Vlasov, G.Wortmann: Solid State Ionics, 1996, 90[1-4], 289-94