Structural and surface properties of zinc-tellurite glass doped with silicon dioxide

Abstract

This thesis studied the influence of silicon dioxide (SiO2) on the physical, thermal, structural and surface properties of zinc-tellurite glass. A series of transparent ternary tellurite glass systems with composition (80-x)TeO2–20ZnO–xSiO2, where x = 0 till 0.20 mol% were synthesized via conventional melt-quenching method. The effects of varying SiO2 contents on the glass density, structural characteristics, thermal properties, water contact angle (WCA), surface roughness and surface morphology were investigated. The amorphous nature of the glass was confirmed using X-ray diffraction measurement. The increase in the SiO2 contents reduced the density from 5.55 to 5.53 g.cm-3 and enhanced the molar volume from 25.96 to 26.06 cm3.mol-1. Differential thermal analysis revealed the increase of glass transition temperature (Tg) with the increase of SiO2 contents. The thermal stability factor was found to vary between 79.9 to 81.5°C depending on the glass composition. Glass morphologies were characterized using atomic force microscopy and WCA measurements. Glass surface roughness as much as 10 nm was attained which is higher than normal glass. The optimal value for WCA was discerned to be 101° and the minimum surface energy was found to be 0.06 N.m-1 for glass sample with 0.1 mol% of SiO2 indicating a glass with low wettability compared to other zinc-tellurite glass. The structural characteristics of glass samples were investigated using Fourier transform infrared (FTIR) spectroscopy in the range of 600 – 4000 cm-1. The FTIR results showed the tellurium atom coordination changes from TeO4 to TeO3 with the increase of SiO2 contents. For TeO4 coordination, the infrared band peaks occurred between 642.8 and 661.7 cm-1 whereas for TeO3, the peaks were observed between 784.7 and 773.1 cm-1. Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy were performed on the glass sample. The surface morphology of glass system appeared rougher with the addition of SiO2 content up to 0.1 mol% which is better compared to normal glass. Overall, the physical, thermal and structural properties of the proposed zinc-tellurite glass system were marginally changed while the surface properties were significantly improved with the inclusion of SiO2.