Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Analysis of structural modifications in γ-irradiated PbO–B2O3–SiO2 glasses by FTIR spectroscopy
Introduction
There has been extensive study of the structure of borosilicate glasses by using several techniques as this system has a wide variety of technological applications such as optical lenses, nuclear waste materials, shielding materials and in electronic industry [1], [2], [3], [4], [5], [6], [7], [8], [9]. The low melting PbO–B2O3–SiO2 are widely used in semiconductor microelectronics for obtaining passive and insulating layers [10], [11]. For this reason it is important to study the influence of various external factors on this glass system [12]. The optimal engineering performance of glasses is dominated by its structure and change in specification within glass network with even small change in composition or processing can have large effects on the properties. The knowledge of the glass structure before and after irradiation is a prerequisite for understanding the structural evolution of glasses under long term irradiation [13]. The investigation of radiation effects leads to a better understanding of the intrinsic structure as well as the alterations, which results from the interaction with radiation. For this reason it is important to study the influence of irradiation on borosilicate glasses [14], [15], [16], [17], [18], [19], [20]. A number of studies on borosilicate glasses [21], [22], [23], [24] have been reported for irradiation effects on optical, electrical and physical properties of glasses by using density, UV–VIS, XPS, EPS and Raman spectroscopic techniques [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38]. Much information on this subject can also be provided by vibrational infrared spectroscopy and spectra of glasses can be generally interpreted by considering the vibrations of structural fragments from which the glass network can be built [39], [40], [41], [42].
Therefore objective of this work is to produce insight into the structural changes that occur due to γ-irradiation in lead borosilicate glasses by using FTIR spectroscopy. Lead content variation from 0.30 mol fraction to 0.75 was chosen since absorption of gamma rays increases with increasing HMO content. The present work will lead to fundamental understanding of γ-irradiation induced structural modifications in lead borosilicate glasses.
Section snippets
Experimental details
Commercial grade chemicals of PbO, SiO2 and B2O3 (Aldrich Chemical Company) having 99.99% purity level were used as starting materials. Chemical data for the constituent oxides is shown in ternary phase diagram (Fig. 1). Samples were prepared by using conventional melt-quenching technique. Appropriate amounts of oxides were mixed together using pestle mortar for half an hour. The platinum crucible-containing batch was then placed in an electric furnace capable of reaching a temperature of 1400
Results
Fig. 2, Fig. 3 show the baseline corrected normalized infrared spectra of Pb1 glasses before irradiation and after 50 Gy, 500 Gy, 4 kGy of irradiation, respectively. To get quantitative information about the change in structure of Pb1 due to irradiation, the difference between irradiated and unirradiated spectra have been shown in Fig. 4 for 50 Gy, 500 Gy and 4 kGy, respectively. Similarly Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11, Fig. 12, Fig. 13 show spectrum before irradiation,
Before irradiation
The structure of borate glasses as a rule is represented in the form of a three dimensional network whose nodes are occupied by threefold or fourfold coordinated boron atoms. The structural unit in silicate glasses mainly consist of SiO4 tetrahedron and IR absorption spectrum of Si–O stretching region is dominated by a band at 1060 cm−1; whereas the boron structure gives infrared bands around 1000 cm−1 due to stretching vibrations of BO4 tetrahedron [44]. In Fig. 2, the position and intensity of
Summary
It can be summarized that irradiation leads to structural changes by breaking the bond between BO3 trigonal and SiO4 and BO4 tetragonal structural units. This, leads to increase in non-bridging oxygen ions and increase in formation of super structural units is also observed due to irradiation. The glass with a high amount of PbO (75%) has a more pronounced response to irradiation and diminished intensity of the tetrahedral structural units is observed.
Acknowledgements
The authors gratefully acknowledge Ms. Elena Mattoni, University of Rome 3, Italy and Angelo Pasquali, ENEA, Casaccia, Roma, Italy for there kind cooperation to perform the measurements.
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