Investigations on ion transport mechanism in the new Ag+ ion conducting
quaternary solid electrolyte systems: (1 − x)[0.75AgI: 0.25AgCl]: xKI, where
0 < x < 1 in mol. wt.%, are reported. The quaternary systems were
prepared by solid solution reaction of an alternate host: `a quenched
[0.75AgI: 0.25AgCl] mixed system/solid solution', instead of the traditional
host salt AgI, and KI. The compositional dependent conductivity studies on
the quaternary systems identified the composition: 0.7[0.75AgI: 0.25AgCl]:
0.3KI, as the Optimum Conducting Composition (OCC) having conductivity
σ ~ 5.9 × 10−3 S cm−1 at 27 °C. For
direct comparison of the room temperature conductivity behaviour of the
quaternary OCC, AgI-based ternary solid solution composition: 0.8AgI: 0.2KI,
resulting into the well-known superionic system: KAg4I5, has also
been synthesized in the identical manner which exhibited σ ~ 1.12 × 10−2 S cm−1 at 27 °C. The conductivity of
newly synthesized quaternary OCC was slightly lower than that of as prepared
ternary KAg4I5. However, in the open ambient conditions $\sigma $
of OCC sample remained practically stable for over hundred hours while that
of KAg4I5 decreased by more than two orders of magnitude in the
same duration. The phase identification and material characterization
studies on the quaternary OCC have been carried out using XRD and DTA
techniques. The ion transport mechanism has been characterized on the basis
of experimental studies on some basic ionic parameters viz. conductivity
($\sigma $), ionic mobility ($\mu $), mobile ion concentration (n), ionic
transference number (tion) and ionic drift velocity (vd). Solid
state batteries have been fabricated using the newly synthesized quaternary
OCC as well as KAg4I5 as electrolytes, sandwiched between Ag/I2 electrode couple and the cell potential discharge performances have
been studied under varying load conditions.