Influence of Fe3+ and Mn2+ Ions on Structural, Thermal, Optical and Mechanical Properties of Mixed Alkali Zinc Borate Glass System

Abstract

The thesis contains the systematic study on the synthesis and characterization of two and three alkali zinc borate glass systems prepared by melt-quenching method. The structural, optical, thermal and mechanical properties are studied in detail. The non-linearity observed in the mechanical, thermal and structural properties of alkali zinc borate glasses with nominal composition 5Li2O-(25-x)K2OxNa2O-60B2O3-10ZnO (x= 0, 5, 10, 15, 20 and 25 mol %) strongly suggests that there exists a strong mixed alkali effect (MAE) in this systems. It is also observed that the MAE is much stronger in three alkali doped system compared to that of two alkali doped glass system. The TMO doped 5Li2O-xK2O-(25-x)Na2O-60B2O3-(10-y) ZnOyTMO (x= 0 and 5 mol% and y= 0 and 0.1 mol%, TMO= Cr2CO3, MnO2, Fe2O3, Co3CO4, and Ni2CO3) glass system revealed the presence of transition metal ions in specific valence and coordination states in the glass matrix. This results in varied optical absorption and hence, is responsible for the colour of the prepared glasses. Chromium and cobalt in both two alkali and three alkali glass matrix favors high valence and coordination states and therefore exhibit the intense colour. The detailed comparative studies of Fe3+ and Mn2+ ions doping on the properties of two alkali 5Li2O-25Na2O-60B2O3-(10-y)ZnO-yTMO (y = 0, 0.1, 0.3, 0.5, 0.7 and 0.9 mol%, TMO= Fe2O3 and MnO2) glass system with that of the three alkali 5Li2O-xK2O-(25-x)Na2O-60B2O3-(10-y)ZnO-yTMO (x = 0 and 5 mol%, y= 0, 0.1, 0.3, 0.5, 0.7 and 0.9 mol%, TMO= Fe2O3 and MnO2) glass system is done. Fourier Transform Infrared (FTIR) and Raman spectroscopy studies reveal that both Fe2O3 and MnO2 act as network modifiers. Both Fe2O3 and MnO2 are observed to enhance the thermal stability of these system of glasses. These glass systems therefore are good host materials for optical fiber fabrication which yield a crystal-free fiber. Optical band gap energy, Eg, of the studied glass systems is found to reduce with increasing Fe2O3 and MnO2 content. Mechanical strength and fracture toughness of the prepared glass samples determined using Vickers micro-indentation technique, exhibit better mechanical properties with the incorporation of Fe2O3 and MnO2 content. The inclusion of Fe2O3 and MnO2 has proved to be of great importance intailoring the properties of the glass systems to make them promising candidates for optical filters.