Conductivity percolation transition of the Agx(Ge0.25Se0.75)100-x system glasses

PIARRISTEGUY, A.; CONDE GARRIDO, J.; MARIA ANDREA UREÑA; FONTANA, M.; ARCONDO, B.

JOURNAL OF NON-CRYSTALLINE SOLIDS

Elsevier

Año: 2007 vol. 353 p. 3314 - 3317

0022-3093

The ionic conductivity of several chalcogenide glasses increases abruptly with the mobile ion addition from typical values of insulating materials (10-16-10-14W-1cm-1) to values of fast ionic conductor (10-7-10-1 -W-1cm-1). This change is produced in a limited concentration range pointing a percolation process. In a previous work [1] the transition from semiconductor to fast ionic conductor of Agx(Ge0.25Se0.75)100-x glasses was detected at x @ 10 at. % in the form of a steep change in the conductivity Agx(Ge0.25Se0.75)100-x glasses with x £ 28 at. %, prepared by a melt quenching method, are investigated by impedance spectroscopy in the frequencies range 5Hz - 2MHz at different temperatures, T, from room temperature to 363K and by DC measurements at room temperature. The conductivity of the glasses, s, was obtained as a function of the silver concentration and the temperature. For x ³ 10 our results are in agreement with those reported by Kawasaki but, for lower values of x, the conductivity decreases more smoothly as it was observed in, other chalcogenide systems [2]. The percolative transition was observed in the range 0 £ x £ 1. The temperature dependence of the ionic conductivity follows an Arrhenius type equation s=(so/T).exp(–Es/kT). The activation energy of the ionic conductivity, Es, and the pre-exponential term,so, are calculated. The results are discussed in connection with other chalcogenide and chalcohalide systems and linked with the glass structures.