ion. As previously mentioned, some theories also assume an order that extends
further than polyhedron dimensions, which constitutes intermediate-range order
[18, 34]. It can generally be assumed that the dimensions of such areas do not
exceed several dozen Å. Therefore, the fundamental conditions for using a given
experimental method in studies on glass structures should be that it yields information on structure fragments with such small dimensions.
There are some measurement methods and techniques that meet the abovementioned condition; however, the most commonly used are spectroscopic methods. Spectroscopic methods are primarily molecular spectroscopy, which includes
vibrational, nuclear magnetic resonance and electron paramagnetic resonance
spectroscopy. Among them, a very important, if not the most important, one is
vibrational spectroscopy, i.e., infrared (IR) spectroscopy and Raman spectroscopy.
Using each of these methods, vibration frequencies of constituent atoms or their
coordination groups can be determined. On that basis, conclusions can be made
about the arrangement of atoms in a molecule, as well as the type of chemical bonds
between the atoms [35], and as a consequence about the aforementioned
short-range order. Thus, vibrational spectroscopy is considered a very important
tool for glass structure studies.
15.2.1 Decomposition of IR Spectra of Glasses
One of the difficulties in interpreting IR spectra is coincidence of bands, which
causes the formation of indistinct signal envelopes consisting of overlapping
maxima. This is the result of the large full width at half maximum (FWHM) of
certain bands characteristic for spectra received from analyzing amorphous bodies.
IR spectra decomposition is a mathematical procedure, in which spectra obtained
during measurement are subjected to the appropriate procedure in order to receive
individual component bands with precisely defined parameters. From this, much
more information can be obtained that allows for an in-depth interpretation.
Aside from several factors characteristic for all solids, the complex form of
amorphous body spectra is influenced by a number of additional phenomena
associated with the specific structure of the glassy state. Silicate glass spectra, while
similar to spectra of their respective crystalline substances, exhibit several separate
features only present in the glass phase. Compared to analogous crystalline spectra
bands originating from lattice, vibrations disappear and mainly those associated
with short-range order remain. The bands have a significantly larger full width at
half maximum and an altered shape. This is the result of, inter alia, a large distribution of lengths and bond angles, as well as disorder in mutual orientation of the
structure fragments. Widening the bands leads to their coincidence and at the same
time a decrease in the number of well-defined maxima. According to Griffiths and
Pariente [36], the number of separated bands N can be expressed using the
following correlation:
464
W. Mozgawa et al.
further than polyhedron dimensions, which constitutes intermediate-range order
[18, 34]. It can generally be assumed that the dimensions of such areas do not
exceed several dozen Å. Therefore, the fundamental conditions for using a given
experimental method in studies on glass structures should be that it yields information on structure fragments with such small dimensions.
There are some measurement methods and techniques that meet the abovementioned condition; however, the most commonly used are spectroscopic methods. Spectroscopic methods are primarily molecular spectroscopy, which includes
vibrational, nuclear magnetic resonance and electron paramagnetic resonance
spectroscopy. Among them, a very important, if not the most important, one is
vibrational spectroscopy, i.e., infrared (IR) spectroscopy and Raman spectroscopy.
Using each of these methods, vibration frequencies of constituent atoms or their
coordination groups can be determined. On that basis, conclusions can be made
about the arrangement of atoms in a molecule, as well as the type of chemical bonds
between the atoms [35], and as a consequence about the aforementioned
short-range order. Thus, vibrational spectroscopy is considered a very important
tool for glass structure studies.
15.2.1 Decomposition of IR Spectra of Glasses
One of the difficulties in interpreting IR spectra is coincidence of bands, which
causes the formation of indistinct signal envelopes consisting of overlapping
maxima. This is the result of the large full width at half maximum (FWHM) of
certain bands characteristic for spectra received from analyzing amorphous bodies.
IR spectra decomposition is a mathematical procedure, in which spectra obtained
during measurement are subjected to the appropriate procedure in order to receive
individual component bands with precisely defined parameters. From this, much
more information can be obtained that allows for an in-depth interpretation.
Aside from several factors characteristic for all solids, the complex form of
amorphous body spectra is influenced by a number of additional phenomena
associated with the specific structure of the glassy state. Silicate glass spectra, while
similar to spectra of their respective crystalline substances, exhibit several separate
features only present in the glass phase. Compared to analogous crystalline spectra
bands originating from lattice, vibrations disappear and mainly those associated
with short-range order remain. The bands have a significantly larger full width at
half maximum and an altered shape. This is the result of, inter alia, a large distribution of lengths and bond angles, as well as disorder in mutual orientation of the
structure fragments. Widening the bands leads to their coincidence and at the same
time a decrease in the number of well-defined maxima. According to Griffiths and
Pariente [36], the number of separated bands N can be expressed using the
following correlation:
464
W. Mozgawa et al.