Estimation of energies of Ag+ ion formation and migration using transient ionic current (TIC) technique

Transient ionic current (TIC) and impedance spectroscopy techniques were employed to measure the Ag+ ion mobility (ω) and conductivity (σ) respectively of AgI in both β- and α-phases. Subsequently, the mobile ion concentration (n) was calculated using σ and μ data. σ, μ and n show thermally activated type behaviour in both the regions of the phase transition. From the log μ versus 1/T and log n versus 1/T Arrhenius plots, the energies of migration and formation of mobile silver ion were estimated as 0.14 and 0.15 eV respectively in the β-phase and 0.05 and 0.006 eV respectively in the α-phase. The extremely low value of energy of formation in the α-phase suggested that a negligibly small number of mobile ions is thermally added to the large n already existing in this phase. On the basis of these experimental studies, it is concluded that the large increase of σ in αAgI is predominantly due to an abrupt increase of mobile ion concentration. The contribution of ionic mobility to the total conductivity is small.