Synthesis, characterization and electrical properties of CdI2 doped Al2O3 and TiO2 superionic conductors

Highlights: → Al2O3 and TiO2 doped CdI2 composites have been prepared at different composition. → The prepared composites were characterized by XRD, DSC and SEM. → The electrical conductivity shows two- to three fold increment as compared to pure CdI2 in the composition range x = 0.3-0.5 mol fraction of the dopants. → The main reason behind this is the role played by the interface region which itself is a disordered region where defect formation and migration enthalpies are notably reduced. - Abstract: Superionic conductors were prepared by admixing metallic oxides (alumina and titania) with cadmium iodide in different proportions using direct mixing method. The synthesized materials were characterized by various qualitative techniques such as XRD (X-ray diffraction), DSC (differential scanning calorimetry) and SEM (scanning electron microscopy). Pure CdI2 shows the standard pattern which corresponds to β-phase stable at room temperature, however, the diffractograms of the mixtures shows two phase nature of the materials with no effect of the second phase on the peak positions of the first, i.e. CdI2. DSC curves also confirmed the formation of composite. SEM micrographs show the presence of great number of space charge regions which are very important in creating a great number of surfaces which in turn act as additional sources of point defects. It was also found that the conductivity of CdI2 increases with mole fractions of dopants till x = 0.5 for alumina and x = 0.3 for titania. Arrhenius equation was used to study the temperature dependence of electrical conductivity and the activation energy of pure cadmium iodide was found to be 0.792 eV.