MODIFICATION OF THE GLASS STRUCTURE
PRODUCED BY THERMAL PREHISTORY
N.A. Bokov1, V.L. Stolyarova2
1
Institute of Silicate Chemistry of the Russian Academy of Sciences,
Sankt-Petersburg, Russia
2
Sankt-Petersburg State University, Sankt-Petersburg, Russia
Abstract. It was shown the possibility of the modification the structure by the thermal
prehistory of the oxide glass. The experimental results of the changes of the visible
light scattered intensity after temperature jumps in the glass transition region of oxide
glass were discussed. The influence of the thermal prehistory of the sample on the
scattered intensity was studied. The effect of the voltage and the mechanical load on
the process of the modification of the glass structure was observed. The universal
character of the nonlinear coupling of the laser irradiation with the glass structure was
found. The glass samples with modification structure have been prepared by the
quenching technique.
INTRODUCTION
Recently, it was found that the temperature dependence intensity of the
scattering of visible light by oxide glasses showed a peak in the glass transition region
[1-3]. As it was shown that the height and location of the peak observed were very
strongly depended on the thermal prehistory of the glass and the sample size. Taking
into account these features it is assumed that the appearance of the peak is associated
with the arising of the non-equilibrium fluctuations produced by coupling between the
hydrodynamic modes [4, 5].
The striking feature of this phenomenon consists in that the development of the
scattered intensity peak is attended by considerable change in the halo of the primary
light beam passed through the sample. The detail investigation of this phenomenon
had shown that the development of the peak was accompanied by appearance of the
diffraction pattern in vicinity of the light beam passing through the sample [6, 7]. At
present time the reasons of the appearance of this effect are not clear. Nevertheless it
is clear that this phenomenon connected with the effect of nonlinear interaction of the
laser irradiation with the structure of glass. The most important feature of this
phenomenon is the application of the small power laser irradiation. It can be assumed
that the glass structure is the highly unstable state at the moment corresponding to the
peak of the scattered intensity.
The additional arguments in favor of this assumption were obtained by the study
of the influence of voltage and the mechanical load on the behavior of the scattered
intensity.
EXPERIMENTAL PROCEDURE
The scattered light intensity was measured at the angle 900 for the wavelength
of incident laser radiation λ = 4880 Å. The laser beam was focused on the sample by a
long-focus lens. The power density of radiation at the focus was approximately equal
to 500 mW/mm2.
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The primary light beam passed through the center of the sample along the
largest edge. The magnitude obtained experimentally was the absolute value of
polarized Vv component of scattered light intensity, where the index denotes the
polarization status of the incident beam and capital letter stands for the orientation of
the polarizer before the detector. For the observation the speckle, the light beam
passed through the sample was projected on a screen and was recorded with the
digital camera.
The usual experimental procedure for the study of the behavior of material
characteristics depending on thermal prehistory of a glass in the glass transition region
is the method of temperature jump, when the temperature of a sample is rapid
changed and this is followed by isothermal relaxation. Namely this technique was
used for the study of the scattered intensity and observation of the speckle [2-7].
According to this scheme, the sample under study was preliminary stabilized at the
temperature Tst for the time tst and then the temperature was abruptly increased to Tobs
at which the required parameters were measured as a function of the time t.
The objects under investigation were the phosphate glass contained
9.4Na2O*57.7ZnO *32.9P2O5 (mol%) and silicate glass STK-3 commercial glass
containing silica, boron, and barium oxide. Aluminium, zinc, and lanthanum oxides
were also the additives in STK-3. The phosphate glass was synthesized under
laboratory conditions. Silicate glass was prepared industrially. The glass transition
temperature Tg of phosphate glass and silicate glass were equal to 370 and 6400,
respectively.
The glass samples were polished in the form of rectangular prism. The sample
sizes of phosphate glass and silicate glass were 12.214.511.4 and 121714 mm,
respectively.
RESULTS AND DISCUSSION
The data for the phosphate glass were obtained in two experiments carried out
under the following conditions: (1) Tst = 3710, tst = 72 h, and Tobs = 4000 and (2) Tst =
3560, tst = 120 h, and Tobs = 4020.
The results of the first experiment are presented on Fig. 1. As seen from the
upper of Fig. 1, after the stabilization of the sample at the temperature 3710 and the
subsequent temperature jump ΔT = 390 the component Vv reaches a maximum value
of 1510-6 cm-1 within 7 min and then recovers its initial value of 510-6 cm-1 within
11 min. A series of photographs that demonstrate the behavior of the light passed
through the sample are shown in the lover part of Fig. 1. The laser beam spreading
and the formation of set of diffraction ringers are clearly seen in fig. 1b and 1c. A
comparison of the upper and lower parts of Fig. 1 shows that both effects are most
pronounced when the Vv component reaches a maximum (i.e., at  7 min).
The second experiment was performed to elucidate the possibility of using the
quenched technique for fixing the specific glass structure responsible for the above
diffraction effects. For this purpose, the experimental conditions were changed in
such way as to retard the processes proceeding after the temperature jump. As a result,
we succeeded in increasing the lifetime of the Vv maximum by a factor of
approximately 2.
Over period of 12 min, the experiment was performed according to previous
scheme. Three typical images (photographs) of the light beam on the screen for this
time interval are displayed in Fig. 2a, 2b, and 2c. It is evident that they are
qualitatively similar to the photographs shown in Fig. 1. However, in the second
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Intensity Vv x
6
10 , cm
-1
experiment, within 12 min, which corresponds to the maximum value of Vv
component, the power supply of the heater was turned off. This resulted in cooling of
the sample to the room temperature at a mean rate of 50/min. As can be seen from Fig.
2d, the passage of the laser beam through the sample quenched in such a manner leads
to typical diffraction pattern.
17
15
13
11
9
7
5
3
0
5
10
Time, min
15
a
b
c
d
20
25
Fig. 1. Time dependence of the Vv component of the
scattered light and photographs of the laser beam passed
through the phosphate glass sample in the first experiment a
different instants of observation t = (a) 0, (b) 4, and (c) 7, and
(d) 12 min.
The examination of the quenched sample at room temperature revealed that this
sample possesses an increased Vv component as compared to that of initial sample. At
the same time, diffraction pattern displayed in Fig. 2b is observed only when the laser
beam passed through the bulk of the sample subjected to irradiation at high
temperature. It can be assumed that one of the possible reasons for the formation of a
specific region in the sample is a nonlinear interaction of laser radiation with the glass
structure formed at the Tobs.
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a
b
c
d
Fig. 2. Photographs of the laser beam passed through the
phosphate glass sample in the second experiment at different
instants of observation t = (a) 0, (b) 9, and (c) 12 min, and
(d) after quenching.
The similar effect takes place for the silicate glass STK-3. The experiment
carried out under the following conditions: Tst = 6320, tst = 119 h, and Tobs = 6980.
Fig. 3 shows the time dependence of the intensity of Vv component of the
scattered light at an observation temperature 6980. The photographs of the laser beam
passing through the sample are also displayed in Fig. 3. It can be seen from Fig. 3c
and 3d (corresponding to the fifth and sixth minutes of the observation time) that an
increasing of the scattered intensity leads to an increase of the diameter of sport and
the formation of diffraction fringe. However, for silicate glass, the diffraction pattern
turned out to be less pronounced as compared to the phosphate glass.
As in the case of the phosphate glass, the sample characterized by an increased
scattered intensity, as compared to the initial sample, was prepared by the quenched
method. The investigations of the quenched sample at a room temperature revealed
that the diffraction pattern is observed only in the case when the laser beam passes
through the sample volume subjected to irradiation at the observation temperature
Tobs.
It is necessary to mention that the analogous phenomenon was observed for the
sodium germinate glass, contained 12.5 mol% Na2O. The results obtained point out
on the universal character of the effect observed for oxide glasses.
It seems likely that one of possible mechanisms responsible for the appearance
of the diffraction pattern may be produced by the formation of the specific region in
the sample volume, which characterized by the other the refractive index. In that case
this phenomenon is similar the diffraction of the light on a small hole or screen. Since
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Intensity V v
x
10 6, cm -1
this effect related with the nonlinear interaction of the of the small power laser
irradiation with the glass structure formed at the development of the maximum
intensity, it can be assumed that this glass structure is the highly unstable state.
The results confirmed this assumption were obtained in the experiments
connected with the study of the influence of electric voltage and mechanical load on
the kinetics of the changes of scattered light intensity after a temperature jump in the
glass transition region of oxide glasses.
20
18
16
14
12
10
8
6
4
0
2
4
6
8
10
12
Time, min
a
b
c
d
Fig. 3. Time dependence of the Vv component of the
scattered intensity and photographs of the laser beam passing
through the silicate glass sample at different instants of
observation t = (a) 0, (b) 5, (c) 6, and (d) 12 min.
The influence of electric voltage on the time dependence of the scattered light
intensity were conducted with the phosphate glass contained 14.8Na2O*53.1ZnO
*32.1P2O5 (mol%) synthesized under laboratory conditions. The glass transition
temperature Tg of phosphate glass was equal to 3500. The glass sample was polished
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in the form of rectangular disk. The sample diameter was 26.3 mm and its height was
14 mm. The upper and lower sample surfaces were covered with the thin nickel foil,
which were used to lead the electrical voltage. The experiment carried out under the
following conditions: Tst = 3730, tst = 23 h, and Tobs = 4130.
The time dependences of the Vv component of scattered light measured for the
different voltage values were presented on the Fig. 4. As it follows from Fig. 4 that
the insignificant increase of the voltage applied to the sample to 200 – 300 v produce
the increase of the maximum height and the displacement of its position on time scale.
At the further expansion of the voltage to 700 v the maximum height raises
approximately on the 20 % at that maximum position shifts from 14 to 8 min.
13
6
Intensity Vv x 10 cm
-1
12
1
11
2
10
3
9
4
5
8
6
7
6
5
4
0
5
10
15
20
Time, min
Fig. 4. Time dependence of the Vv component of the scattered
intensity by phosphate glass (14.8Na2O*53.1ZnO *32.1P2O5)
at 4130 after the temperature jump from 3730 for the different
voltage values applied to the sample: 0v (1), 200v (2), 300v
(3), 400v (4), 500v (5), and 700v (6).
The influence of mechanical load on the time dependence of scattered light
intensity were conducted with the phosphate glass contained 9.4Na2O*57.7ZnO
*32.9P2O5 (mol%). The glass sample was polished in the form of rectangular prism.
The sample sizes were 121531 mm. The laser beam passed through the sample into
the sample side 1231 mm approximately in the middle of the sample height, i.e. 31/2
= 15.5 mm. The scattered light was registered at angle 900 from the sample side
1531 mm. The sample was subjected to the stress by means of the loads, which
realized by the using the different weights. The weights were placed on the upper rod
end. The underside end of the rod set on the quartz plate, which located on the upper
side of the sample defined by the following edges 1215 mm. The weight mass were
3 and 5 kg. The experiment carried out under the following conditions: Tst = 3530, tst
= 47 h, and Tobs = 4000. The weights were placed on the upper rod end at the moment,
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10 6cm -1
9
8
1
7
2
x
6
3
Intensity Vv
when the temperature ran up to T obs = 4000 corresponding at the beginning of the
measurement of the scattered light intensity.
Figure 5 demonstrates the results obtained for the three conditions: (1) the rod
without the weight, (2) the rod with the weight 3 kg, and (3) the rod with the weight 5
kg. As it follows from Fig. 5 that the increase of the load applied to the sample
produce the decrease of the maximum height and the displacement of its position on
time scale to the larger time.
5
4
3
2
0
5
10
15
20
Time, min
Fig. 5. Time dependence of the Vv component of the scattered
intensity by phosphate glass 9.4Na2O*57.7ZnO *32.9P2O5 at
4000 after the temperature jump from 3530 for the different
load values applied to the sample: 0 kg (1), 3 kg (2), 5 kg (3).
Taking into account of the insignificant values of the enclosed impacts the
results obtained confirm the assumption that the glass structure is the highly unstable
state at the moment, which corresponded to the peak of the scattered intensity. It
should be mentioned that in general the obtained results agree qualitatively with the
analysis of the influence the pressure, tangential stress, and electric fields on the
kinetic of the glass transition process [8, 9].
The analysis of the present results shows that the development of the diffraction
pattern was greater than the scattered intensity maximum was higher. The obtained
results shown that the maximum height was determined by the thermal prehistory of
the glass, which depended on the stabilization Tst and observation Tobs temperatures,
and the time stabilization tst. The present results indicate that on the maximum height
expose the using not only the thermal influence. Namely, as it was shown above, the
increase of the voltage applied to the sample produce the increase of the maximum
height. This circumstance may be of use for the intensification of the process of
nonlinear interaction of the light radiation with the glass structure.
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CONCLUSION
The obtained results show that the universal phenomenon of the evolution of
scattered intensity in the glass transition of oxide glasses is attended by the formation
of diffraction pattern. The observed effect is associated with the nonlinear interaction
of laser radiation with the glass structure. The kind of this phenomenon consists in the
application of the small power laser irradiation, which has property to modify the
refractive index in the glass volume. The observation carried out in the present work
revealed that the glass structure is the highly unstable state when the scattered
intensity amounted to the maximum values. It was shown that the process of nonlinear
interaction of laser radiation with the glass structure may be amplifies by the electric
voltage applied to the sample under investigation. For the practical purposes, it may
be useful to modify the refractive index in the glass volume.
ACKNOWLEDGEMENT
This study was carried out based on the financial support by the Russian
Foundation for Basic Research according to the project N 04-03-32886.
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