Effet de formateur mixte sur la conductivité ionique des verres du système Ag₂O-B₂O₃-TeO₂

Abstract
The so-called mixed anion effect is a non linear enhancement for ionic conductivity with the composition. It is observed for alkali or silver conducting glasses when two different network formers are associated. We have synthetised glasses in the system 0.3 Ag₂O-0.7 [x B₂O₃ (1-x) Te₂O₄] with [MATH]. From optical, X Ray, electronic microscopy observations, Tg and electrical conductivity measurements, these glasses seem homogeneous. Isothermal conductivity curves define two maxima near x = 0.25 and x = 0.75. The conductivity enhancement may reach one order of magnitude compared to a additive behavior. A thermodynamic approach is proposed and the two maxima for conductivity measurements are qualitatively explained by an enhancement of the partial free energy for the limiting compositions due to an endothermic mixture.