Maiden attempt has been made for the direct estimation of the contributions of silver and copper ions to the ionic conductivity in superionic solids obtained in CuI-doped silver oxysalt systems. The application of the combined electrolysis and EDS techniques towards qualitative and quantitative analyses of the mobile ionic species in solid electrolyte systems having more than one possible mobile ion is reported. These studies confirmed that these electrolyte materials are purely Ag+ conducting up to 50 mol% CuI in xCuI-(100-x)[2Ag(2)O-0.7V(2)O(5)-0.3B(2)O(3)] and xCuI-(100 -x)[Ag2O-0.7MoO(3)-0.3WO(3)] systems and small fraction of t(Cu+) exists above 60 mol% CuI. These solid electrolyte materials exhibited a high ionic transport numbers (t(i)) of >0.985 and the t(i) increases when two glass formers are used. (C) 2007 Elsevier Ltd. All rights reserved.