Impact of high NiO content on the structural, optical, and dielectric properties of calcium lithium silicate glasses

Abstract Glasses with the composition (11.5 − ×) CaO − 23.5Li 2 O − 65SiO 2: × NiO mol. % (0 $$\le \times \leq$$ ≤×≤ 11.5) were synthesized by melt-quenching method. And a number of physical parameters have been established. The refractive index and energy gap were also used to estimate the metallization criterion, where these glasses have shown values fallings between high (insulators) and low (metals), indicating that they are semiconductors. The XRD pattern shows the amorphous nature of investigated glasses. A number of spectroscopic analyses of the studied glasses were performed, in relation to NiO content, including Fourier transform infrared (FTIR) and UV–Visible diffuse reflectance spectroscopy (DRS). Due to compositional changes, FTIR measurements have revealed structural changes in the glass network. Furthermore, with increasing NiO content, the asymmetrical bands of silicate units increase. The creation of Ni–O–Si bonds in the silicate matrix has been attributed to the introducing heavier Ni +2 as [NiO 4 ] 2− tetrahedral species in substitution of the lighter silicon ion in the [SiO 4 ] 4− network, but it could also operate as a network modifier in glass materials. The Ni 2+ ion may have behaved as a network intermediary, causing more compact structure. The mechanism of charge transfer in the glass compositions under investigation is studied using broadband dielectric spectroscopy. For the first time, the relationship between the hopping time of free ions and dc conductivity is illustrated. All of the glasses under investigation have the same charge transport mechanism. The results suggest the semiconducting nature of these glasses.