Short-range and medium-range structural order in CaO-SiO2-TiO2-B2O3 glasses

Abstract

The present study aimed to provide a deep insight of short-range and medium-range structural order for CaO-SiO2-TiO2-B2O3 glasses. From various prospects, four techniques, FTIR, Raman, XPS and NMR, were simultaneously employed and only the direct evidences indicated from the spectra were used for structural analysis. The FTIR and Raman spectra proved that the main silicon-related units were Q0 (Si), Q1 (Si), Q2 (Si) and Q3 (Si) and the results of Raman fittings revealed that a B2O3 addition resulted in an increase of Q1 (Si) and Q3 (Si) at the cost of Q0 (Si) and Q2 (Si), thus inducing an increasing Degree of Polymerization (DOP). An enhanced DOP generally implied a lower abundance of non-bridging oxygen in the networks, which was further demonstrated by the O1s XPS fittings. Additionally, the 11B NMR spectra indicated that the dominant boron-related groups were BO3 trigonal comprising ring and non-ring BO3 as well as BO4 tetrahedral comprising BO4 (1B,3Si) and BO4(0B,4Si). Furthermore, it was clarified that an increase of B2O3 content promoted the ratios of BO4 (1B,3Si) to BO4 (0B,4Si) and BO4tetrahedral to BO3trigonal, which undoubtedly identified the occurrence of an equilibrium reaction between NBO, BO4 tetrahedral and BO3 trigonal in the glass.