• bands in the range of 1200–800 cm
−1 originating from asymmetrical stretching
vibrations of Si–O bonds taking place inside Si–O–Si (m as Si–O–Si) and Si–O–
Al (m as Si–O–Al) bridges;
• bands in the range of 850–600 cm
−1 originating from symmetrical stretching
vibration of Si–O–(Si, Al) bonds (m s Si–O–Si and m s Si–O–Al);
• bands around 500 cm
−1 originating from bending vibrations of Si–O–Si and
Si–O–Al bonds (d Si–O–(Si, Al)).
The first range is associated with (as in the case of m-SiO 2 ) stretching vibrations
of the Si–O bond. These vibrations take place inside Si–O–Si or Si–O–Al bridges.
However, it should be noted that at high aluminum concentration, it is highly
possible that there is a third kind of bridge bond, i.e., Al–O–Al [59]. The existence
of such bridge should be considered as a type of defect in the aluminosilicate
network. Depending on the contribution of individual bonds in the structure, i.e.,
depending on the Si:Al ratio, the envelope of the spectra changes in that range. In
basic m-SiO 2 glass, there are only Si–O–Si bridges; however, in calsilite (with the
Si:Al ratio equal to 1), only Si–O–Al bridges are present. Therefore, the band at
1107 cm
−1 should be assigned to m as Si–O–Si, and the band at 997 cm
−1 in the
spectrum obtained from a K[AlSiO 4 ] assigned to m as Si–O–Al vibrations. In the
spectra of glasses with orthoclase or leucite composition, both bands (and both
types of bridges in their structures) are present, the positions of which are located
between those previously mentioned. The greater number of Si–O–Al bridges
(lower Si:Al ratio) in leucite than in orthoclase leads to a change in the band
position toward lower wavenumbers.
Of course, the presence of broken Si–O
− bonds and multiple Si=O bonds cannot
be ruled out in the discussed structures, which is made visible in the spectra after
decomposition process (Fig. 15.12a). As in the case of silicate glass analysis
(Fig. 15.10), Fig. 15.12 compares the spectrum obtained from crystalline calsilite
(K[AlSiO 4 ]) with the spectrum of glass with the same chemical composition. The
similarity in the spectra can be noticed; however, the individual bands in the glassy
spectrum exhibit a much greater full width at half maximum. On this basis, it can be
stated that in glass composed of K[AlSiO 4 ], there are domains with calsilite
structure. It can also be confirmed that potassium ions cause the disappearance of
Si=O bonds (no band at around 1200 cm
−1 ).
Based on the spectra of glasses from the K 2 O–Al 2 O 3 –SiO 2 system (Fig. 15.11),
interesting information can be derived from analyzing the pseudo-lattice range, i.e.,
800–650 cm
−1
. In this range, there are bands with relatively small integral intensities; however, in this range, the greatest changes associated with differences in the
composition of the analyzed glasses can be observed. There are at least two bands: a
band assigned to m s Si–O–Si vibrations in the m-SiO 2 spectrum at 800 cm
−1 and a
band assigned to m s Si–O–Al vibrations in the calsilite spectrum at 694 cm
−1 . The
lower aluminum mass leads to a change in the band position in the direction of
lower wavenumber values. m-SiO 2 and glass with calsilite composition constitute
two extreme cases of the network. In the case of m-SiO 2 , there are only Si–O–Si
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W. Mozgawa et al.
−1 originating from asymmetrical stretching
vibrations of Si–O bonds taking place inside Si–O–Si (m as Si–O–Si) and Si–O–
Al (m as Si–O–Al) bridges;
• bands in the range of 850–600 cm
−1 originating from symmetrical stretching
vibration of Si–O–(Si, Al) bonds (m s Si–O–Si and m s Si–O–Al);
• bands around 500 cm
−1 originating from bending vibrations of Si–O–Si and
Si–O–Al bonds (d Si–O–(Si, Al)).
The first range is associated with (as in the case of m-SiO 2 ) stretching vibrations
of the Si–O bond. These vibrations take place inside Si–O–Si or Si–O–Al bridges.
However, it should be noted that at high aluminum concentration, it is highly
possible that there is a third kind of bridge bond, i.e., Al–O–Al [59]. The existence
of such bridge should be considered as a type of defect in the aluminosilicate
network. Depending on the contribution of individual bonds in the structure, i.e.,
depending on the Si:Al ratio, the envelope of the spectra changes in that range. In
basic m-SiO 2 glass, there are only Si–O–Si bridges; however, in calsilite (with the
Si:Al ratio equal to 1), only Si–O–Al bridges are present. Therefore, the band at
1107 cm
−1 should be assigned to m as Si–O–Si, and the band at 997 cm
−1 in the
spectrum obtained from a K[AlSiO 4 ] assigned to m as Si–O–Al vibrations. In the
spectra of glasses with orthoclase or leucite composition, both bands (and both
types of bridges in their structures) are present, the positions of which are located
between those previously mentioned. The greater number of Si–O–Al bridges
(lower Si:Al ratio) in leucite than in orthoclase leads to a change in the band
position toward lower wavenumbers.
Of course, the presence of broken Si–O
− bonds and multiple Si=O bonds cannot
be ruled out in the discussed structures, which is made visible in the spectra after
decomposition process (Fig. 15.12a). As in the case of silicate glass analysis
(Fig. 15.10), Fig. 15.12 compares the spectrum obtained from crystalline calsilite
(K[AlSiO 4 ]) with the spectrum of glass with the same chemical composition. The
similarity in the spectra can be noticed; however, the individual bands in the glassy
spectrum exhibit a much greater full width at half maximum. On this basis, it can be
stated that in glass composed of K[AlSiO 4 ], there are domains with calsilite
structure. It can also be confirmed that potassium ions cause the disappearance of
Si=O bonds (no band at around 1200 cm
−1 ).
Based on the spectra of glasses from the K 2 O–Al 2 O 3 –SiO 2 system (Fig. 15.11),
interesting information can be derived from analyzing the pseudo-lattice range, i.e.,
800–650 cm
−1
. In this range, there are bands with relatively small integral intensities; however, in this range, the greatest changes associated with differences in the
composition of the analyzed glasses can be observed. There are at least two bands: a
band assigned to m s Si–O–Si vibrations in the m-SiO 2 spectrum at 800 cm
−1 and a
band assigned to m s Si–O–Al vibrations in the calsilite spectrum at 694 cm
−1 . The
lower aluminum mass leads to a change in the band position in the direction of
lower wavenumber values. m-SiO 2 and glass with calsilite composition constitute
two extreme cases of the network. In the case of m-SiO 2 , there are only Si–O–Si
476
W. Mozgawa et al.