Dielectric dispersion and impedance spectroscopy of NiO doped Li2SO4–MgO–P2O5 glass system

Abstract

Li2SO4–MgO–P2O5 glasses mixed with a varied quantity of NiO were prepared. Detailed spectroscopic investigations (viz., OA, IR and Raman) spectra were carried out. Optical absorption spectral results indicated that Ni2+ ions in the glass network reside in octahedral (Oh) as well as tetrahedral (Td) sites; these results have also pointed out the growing concentration of Ni2+ ions in Oh sites as NiO concentration is increased up to 0.8 mol%. Results of infrared and Raman spectral studies indicated increased internal chaos in the sulpho-phosphate glass network with an increase of NiO concentration up to 0.8 mol%. Values of dielectric permittivity (both real and imaginary components), a.c. conductivity, σac, are observed to be gradually increasing with NiO content in the concentration range 0–0.8 mol%. Electric moduli spectra have exhibited dipolar relaxation effects and the dipolar relaxation time τ estimated from these spectra exhibited a decreasing trend with the raise of NiO quantity up to 0.8 mol%. The complexes of octahedral Ni2+ ions with oxygen ions are predicted to be the possible dipoles responsible for the dipolar effects. Variation of σac with NiO content exhibited an increasing trend up to 0.8 mol%. Quantitative analysis of this observation indicated ionic contribution to σac is dominant in the glasses containing small quantities of NiO (< 0.8 mol%), whereas in the glasses containing higher quantities of NiO (> 0.8 mol%) polaronic contribution to the conductivity seems to be present. Overall, the results of dielectric properties of studied glass system indicted that the glass with low quantities of NiO (< 0.8 mol%) can be considered as useful material as electrolytes in the solid-state batteries.