Preparation and characterization of glasses from the binary sodium fluoroborate system NaF–B2O3 within the range (10–50 mol% NaF) assessed by structural FTIR, optical and thermal properties and effects of gamma irradiation

Abstract

Extended glasses from the binary system (NaF-B2O3) with (10→50 mol% NaF) were synthesized by the traditional melting-annealing route. These unfamiliar glasses with high extended NaF contents than Na2O were characterized by multi-techniques including optical and FTIR spectral analysis beside measurements of their thermal expansion parameters. The optical (UV–visible) spectra of the glasses reveal obvious transparency except for the appearance of distinct UV absorption due to unavoidable trace ferric ions impurities present within the laboratory chemicals. Structural FTIR spectra indicate that NaF primarily acts the same as Na2O progressively converting some of the BO3 units to produce tetrahedral (BO3F) units and then at a high percent of NaF is assumed to form additional (NaF4) groups and hence the intensity of the bands within the range 800–1200 cm−1 due to combined tetrahedral groups (BO4 + NaF4) is always higher than that for the peaks at the range 1200–1600 cm−1due to vibrational BO3 groups. The thermal expansion data reveal that the dilatometric softening temperature primarily increases due to the formation of compact tetrahedral (BO3F) groups. It is obvious that this unfamiliar (NaF–B2O3) glass does not show an anomalous behavior as that reported for (Na2O–B2O3) glassy system and other alkali-B2O3 glasses in their thermal expansion properties. Gamma irradiation did not show any distinct variations in the FTIR spectra indicating the stability of the structural building groups in this NaF–B2O3 glass system. On the other hand, the optical spectra show the displacement of one of the two broad bands in the UV spectra which is assumed to be due to a photochemical reaction between some Fe3+ ions present as trace impurities and formed freed electrons during the irradiation process.