Electrical conductivity in TlI-TiO2 composite solid electrolyte

Composite materials of formula (1−x)TlI−xTiO₂, x=0-0.7, have been prepared and studied by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy and electrical conductivity. The materials were found to be binary phase systems with titania particles distributed between the grains of thallium iodide. The electrical conductivity got enhanced in the composition range x=0.1-0.5 and then decreased with further increase in the titania content. The behaviour is explained in terms of disordering phenomena at the interface regions and space-charge layers formed in the bulk grains of thallium iodide. Moreover, the increased content of titania in the system leads to the disappearance of order-disorder (β-α) phase transition in thallium iodide, which is usually observed in the pure compound. This behaviour was explained by the stabilizing effect of β-phase at high temperatures and at higher contents of titania. X-ray diffractograms do not show any indication to the presence of α-phase at ambient temperature, i.e. the phase could not be stabilized in the investigated system.