Structural and electrical characterisation of Li2O ∶ TiO2 ∶ SnO2 ∶ P2O5 electrolyte glass

Abstract

Glasses of general formula 50Li₂O ∶ xSnO₂ ∶ (10 − x)TiO₂ ∶ 40P₂O₅ (0.0 ≤ x ≤ 10) were investigated by differential scanning calorimetry, X-ray diffraction and ac impedance, ³¹P solid-state NMR and IR spectroscopies. Three isotropic resonances can be identified in the ³¹P NMR spectra, which have been assigned to various phosphate species. Analysis of the ratios of integrated intensities in the ³¹P spectra leads to models for the Ti and Sn coordination environments. Both TiO₂ and SnO₂ are found to be predominantly network forming with Ti and Sn proposed to be in five- and four-coordinate environments respectively. Analysis of ac impedance spectra collected at low temperatures reveals two forms of permittivity dispersion, viz: high frequency conductivity dispersion and Cole–Cole type relaxation of permittivity. The activation energy of the relaxation frequency of the permittivity dispersion is equal to that of the dc conductivity, which is consistent with cooperative motion of lithium ions. The results also suggest that the observed increase in conductivity with temperature appears to be mainly due to an increase in mobility rather than increase in carrier concentration.