Тhe investigation of X-rays irradiation effect on the mobility of dislocations in LiF crystals
An acoustic pulse echo method at a frequency of 7.5 MHz was used to study the dependence of the absorption α
 and the relative velocity of ultrasound Δv/v₀
 in single crystals of LiF with a residual deformation of ε = 0.65%, at
 300 K in the irradiation dose range 0...1057...
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| Zitieren: | Тhe investigation of X-rays irradiation effect on the mobility of dislocations in LiF crystals / О.M. Petchenko, G.О. Petchenko, S.M. Boiko // Вопросы атомной науки и техники. — 2018. — № 5. — С. 16-20. — Бібліогр.: 43 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860172792472797184 |
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| author | Petchenko, О.M. Petchenko, G.О. Boiko, S.M. |
| author_facet | Petchenko, О.M. Petchenko, G.О. Boiko, S.M. |
| citation_txt | Тhe investigation of X-rays irradiation effect on the mobility of dislocations in LiF crystals / О.M. Petchenko, G.О. Petchenko, S.M. Boiko // Вопросы атомной науки и техники. — 2018. — № 5. — С. 16-20. — Бібліогр.: 43 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | An acoustic pulse echo method at a frequency of 7.5 MHz was used to study the dependence of the absorption α
and the relative velocity of ultrasound Δv/v₀
in single crystals of LiF with a residual deformation of ε = 0.65%, at
300 K in the irradiation dose range 0...1057 R. It was found that an increase in the irradiation dose leads to a noticeable decrease in the damping and the relative ultrasound velocity in the sample as a result of a decrease in the effective density of the dislocation segment L when it is fixed by radiation centers. Based on the results of measurements
of acoustic characteristics, the absolute value of the damping factor of dislocations B is determined and compared
with the literature data obtained from the high-frequency branch of dislocation resonance.
Акустичним імпульсним ехо-методом на частоті 7,5 МГц досліджено залежності поглинання α і відносної швидкості ультразвуку
Δv/v₀ у монокристалах LiF із залишковою деформацією ε = 0,65% при 300 К в
інтервалі доз опромінення 0…1057 P. Виявлено, що збільшення дози опромінення призводить до помітного
зниження згасання і відносної швидкості ультразвуку в зразку через зменшення ефективної довжини дислокаційного сегмента L при його закріпленні радіаційними центрами. На основі результатів вимірювань акустичних характеристик визначено абсолютне значення величини коефіцієнта демпфування дислокацій В і
проведено його порівняння з літературними даними, одержаними за високочастотною гілкою дислокаційного резонансу.
Акустическим импульсным эхо-методом на частоте 7,5 МГц исследованы зависимости поглощения α и относительной скорости ультразвука Δv/v₀ в монокристаллах LiF с остаточной деформацией ε = 0,65% при 300 К в интервале доз облучения 0…1057 P. Обнаружено, что увеличение дозы облучения приводит к заметному снижению затухания и относительной скорости ультразвука в образце вследствие уменьшения эффективной длины дислокационного сегмента L при его закреплении радиационными центрами. На основе
результатов измерений акустических характеристик определено абсолютное значение величины коэффициента демпфирования дислокаций В и проведено его сравнение с литературными данными, полученными по
высокочастотной ветви дислокационного резонанса.
|
| first_indexed | 2025-12-07T17:58:54Z |
| format | Article |
| fulltext |
16 ISSN 1562-6016. ВАНТ. 2018. 5(117)
UDC 539.67:539.374
THE INVESTIGATION OF X-RAYS IRRADIATION EFFECT
ON THE MOBILITY OF DISLOCATIONS IN LiF CRYSTALS
О.M. Petchenko
1
, G.О. Petchenko
1
, S.M. Boiko
2
1
O.M. Beketov National University of Urban Economy in Kharkiv, Kharkov, Ukraine
E-mail: gdaeron@ukr.net;
2
M.Ye. Zhukovskiy Kharkiv National Aerospace University, Kharkov, Ukraine
E-mail: svitlanazagreba7@gmail.com
An acoustic pulse echo method at a frequency of 7.5 MHz was used to study the dependence of the absorption α
and the relative velocity of ultrasound 0/ vv in single crystals of LiF with a residual deformation of = 0.65%, at
300 K in the irradiation dose range 0...1057 R. It was found that an increase in the irradiation dose leads to a notice-
able decrease in the damping and the relative ultrasound velocity in the sample as a result of a decrease in the effec-
tive density of the dislocation segment L when it is fixed by radiation centers. Based on the results of measurements
of acoustic characteristics, the absolute value of the damping factor of dislocations B is determined and compared
with the literature data obtained from the high-frequency branch of dislocation resonance.
INTRODUCTION
One can see from the reviews [1–4] that a lot of the-
oretical and experimental works have been devoted to
the study of the radiation exposure effect on the proper-
ties of crystals. It became known that an increase in the
number of radiation centers in ionic crystals stimulated
the appearance of acoustic effects caused by the interac-
tion of these point defects with mobile dislocations. To
mark out the deposition process onset at dislocations of
different pinning points, the low-frequency methods of
amplitude-dependent internal friction are proved to be
the most effective [1, 2]. With their help, the smallest
changes in the average effective length of the disloca-
tion loop L oscillating in the field of the ultrasonic wave
can be clearly recorded. These changes, by virtue of the
law L
4
[3] have a very significant effect on the
measured attenuation magnitude of ultrasound in the
sample. The noted methods are very sensitive to the
appearance of radiation centers in the crystal, although
their application is fraught with certain difficulties.
Firstly, when a low-frequency wave of high amplitude
is transmitted, deformation by the ultrasound may occur
in the crystal under investigation, which can lead to a
change in both the value of L and the dislocation density
. In addition, at large amplitudes of the ultrasonic
wave, small portions of radiation defects can not exhibit
an appreciable stopping effect on a mobile dislocation.
Therefore, low-frequency experiments often use large
doses of radiation, which can lead to changes in me-
chanical [1, 5–7] and optical [8–17] crystal characteris-
tics.
In this connection, to solve the mentioned problems,
we began to use the amplitude-independent, acoustic
method of the MHz-frequency range [18, 19], which is
highly informative and highly sensitive to the effect of
weak radiation stoppers on the dislocation. Analyzing a
large array of experimental data [18–26, 28, 29] on the
dynamics of dislocations under conditions of various
external influences, it is not difficult to see that only
those results obtained on the descending branch of a
damped dislocation resonance are correct. The experi-
mental data obtained at the low-frequency branch of this
resonance are preliminary in nature and therefore need
serious verification and refinement. Due to this, the pur-
pose of the present paper is to determine the value of the
coefficient of dynamic braking of dislocations B from
low-frequency measurements and a comparison with the
analogous value found from the high-frequency asymp-
tote of dislocation resonance.
MATERIALS
AND EXPERIMENTAL TECHNIQUES
In this paper, we studied the effect of weak X-ray ir-
radiation on the absorption and ultrasound velocity in
LiF single crystals with a residual deformation of 0.65%
at a frequency of 7.5 MHz at a temperature of 300 K.
The samples having parameters 171727 mm and pu-
rity of 10
-4
weight %, obtained by puncturing on cleav-
age planes <100>, were used in the experiments. The
attenuation of ultrasound was measured with the method
of superimposing a calibrated exponent on the reflected
echoes, and the impulse interference method as well as
the selector method [2], realized by the apparatus [27],
were used to measure the velocity. In order to carry out
precise acoustic measurements, the studied samples, in
accordance with recommendations [20–26, 28, 29],
were subjected to fine optical polishing after puncturing,
so that the non-parallelism of their working faces was
± 1 μm/cm, which was monitored with an IKV type
optimeter. An additional estimate of the non-
parallelism degree in the “piezo-quartz-glue-sample”
system could also be obtained in the process of super-
imposing a calibrated exponent on a series of reflected
pulses observed on an oscilloscope screen. To remove
internal stresses that could arise during machining of
samples, they were annealed for ~ 12 hours in MP-2UM
muffle furnace at a temperature of ~ 0.8Tm (where Tm is
the melting temperature), followed by slow cooling to
room temperature. In order to implant “easy-moving”
(mobile) dislocations into the crystal, it was preliminari-
ly deformed to obtain a residual deformation of
= 0.65%. The deformation of the samples was carried
out by compression in a rupturing machine of the In-
stron type at a speed of ~ 10
-5
s
-1
. Under this defor-
mailto:gdaeron@ukr.net
mailto:svitlanazagreba7@gmail.com
ISSN 1562-6016. ВАНТ. 2018. 5(117) 17
mation regime, slip bands do not arise, and etch pits
uniformly cover the etched surface of the crystal [20–
26, 28, 29], which allows us to determine the dislocation
density in crystals quite accurately. The technology for
the dislocation component's isolation from the total ab-
sorption was the same as in [20–26, 28, 29].
The irradiation of the investigated LiF crystals was
performed at a standard X-ray unit of the URS-55 type,
which provided the radiation dose rate 0.11 R/s at the
location of the investigated crystal. To avoid the ap-
pearance of possible inhomogeneities in the sample
caused by internal mechanical stresses [1, 4], each of
the 4 lateral faces parallel to the long axis of the crystal
was irradiated alternately for 20 min, which correspond-
ed to a total dose of 1057 R.
RESULTS AND DISCUSSION
Fig. 1 shows the results of studying the dislocation
absorption's dependence α on the time of X-rays
irradiation for LiF samples with a residual deformation
of = 0.65%. It is evident that with an increase in the
irradiation time of the sample – the attenuation of
ultrasound decreases sharply. It should be noted that
even after the first 20 min of irradiation, the attenuation
decreased by 0.34 dB/μs, and during the remaining
measurement time its value decreased by another
0.3 dB/μs. Completely expected were the results, shown
in Fig. 2, obtained on the same sample when measuring
the relative velocity of ultrasound 0/ vv , where
v = vv 0 ( 0v – speed in the initial annealed sample,
measured at a frequency of 217.5 MHz).
Fig. 1. The dependence of the dislocation ultrasound
absorption on the irradiation time in LiF crystals with
a residual deformation of 0.65% at T = 300 K
Fig. 2. The dependence of the relative propagation
velocity of ultrasonic waves on the irradiation time
in deformed (0.65%) LiF crystals at T = 300 K
One can see that as the irradiation time increases, the
effect of decreasing the relative propagation velocity of
the ultrasonic wave in the crystal is observed. We
couldn't help note, that an analogous behavior of the
acoustic characteristics in the course of the irradiation
time increasing was also found earlier on NaCl crystals
[18]. Using the data on 0/ vv and α, in paper [18] the
calculation of the dislocation structure's parameters
and L was carried out by means of formulas for low
frequencies [3]:
24
6 2 0
2
( / )
8.68 10
v vB
f
Gb
, (1)
21
0
6
688
10
2
1 /
v/vB
C
.v
L
. (2)
The values of the dislocation characteristics and L
were determined in [18] as a result of calculations, and
they were found to be 1.2∙10
11
m
-2
and 1.3∙10
-6
m, re-
spectively, and it was assumed that B = 10
-5
Pa∙s.
To clarify the correctness of the results presented in
[18] and for the comprehensive verification of the theo-
ry [3], we suppose, that it is important to calculate the
coefficient of viscosity B from the formula (1) and
compare it with the estimation of B found in [24, 29] on
the high-frequency asymptote of a damped dislocation
resonance. The expression for the value B, using formu-
la (1), takes the form:
20
246
2
10688 v/vf.
bG
B e
, (3)
where e is the density of dislocations found by the
etch pit method; Ω is the orientation factor; C is the lin-
ear tension of the dislocation; G is the shear modulus;
b is the value of the Burgers vector; f is the operating
frequency of the ultrasonic wave.
With the help of the substituting into the formula (3)
the values Ω = 0.311 [24, 29]; G = 3.533∙10
10
Pa [24,
29]; b = 2.85∙10
-10
m; f = 7.5∙10
6
Hz; e = 1.74∙10
10
m
-2
[24, 29], as well as the data on 0/ vv and α shown in
Figs. 1, 2, there were formed the dependence of the
damping constant B on the irradiation time, presented in
Fig. 3.
Fig. 3. The dependence of the viscosity coefficient B
on the irradiation time in LiF crystals with a residual
deformation of 0.65% at T = 300 K
0 50 100 150
0,2
0,4
0,6
0,8
f = 7,5 MHz
LiF
0,65%
,d
b
/
s
t, min
0 50 100 150
50
100
150
200
250
f = 7,5 MHz
LiF
0,65 %
v
/v
0
,1
0
-4
t, min
0 50 100 150
0,0
0,5
1,0
1,5
.
В
,1
0
-
6
P
a
s
LiF
0,65 %
Data: Data1_B
Model: Boltzmann
Chi^2/DoF = 0.00014
R^2 = 0.99837
A1 0.10231±0.22504
A2 1.05063±0.00783
x0 5.334 ±9.17242
dx 18.76079 ±2.92759
f = 7,5 MHz
t, min
18 ISSN 1562-6016. ВАНТ. 2018. 5(117)
It is obviously that the value of B is irrespective of
the fact that the irradiation dose, and a small deviation
in the first ~ 30 min of exposure can be a consequence
of the fact that the initial deformation of 0.65% lowers
the value of the resonant frequency. Because of this,
according to [2, 3], the initial condition ω/ωm«1 may not
be fulfilled strictly enough to simplify the derivation of
relations (1) and (2). Measuring on the same LiF crys-
tals the frequency dependences of the dislocation reso-
nance in [24, 29], we've got the opportunity to found
that before the irradiation, the resonance maximum was
at the frequency of 14 MHz, and after 20 and 40 min of
irradiation it moved to positions 25 and 40 MHz respec-
tively. At the same time, the working frequency of
7.5 MHz, at which the values of α and 0/ vv were
measured in this paper, already appeared on the ascend-
ing branch's linear part of the frequency profile [3],
where the condition ω/ωm«1 is satisfied.
Due to the comparing the absolute value of
В = 1.05∙10
-6
Pa∙s, obtained in this paper with the esti-
mate В = 3.7∙10
-5
Pa∙s, found out from the high-
frequency branch of dislocation resonance [24, 29] by
using the “reference” value e , determined by the
method of selective etching, was revealed the fact that
these estimates of B are more than an order of magni-
tude different. Such a difference, according to [30], is
caused by the impossibility of describing acoustic
measurements conducted over a wide range of frequen-
cies by using a single damping mechanism in the
framework of the dislocation theory [3]. It is rather use-
ful to take the obtained results into experiments, where
the influence of various factors [31–43] on the mobility
of dislocations in crystals is studied.
СONLUSIONS
There were investigated the effect of x-ray irradia-
tion in the dose range 0...1057 R on the dislocation ab-
sorption 0/ vv and the relative ultrasound velocity in
LiF single crystals, deformed to 0.65% and measured at
a frequency of 7.5 MHz at room temperature. It was
established by experiments that, after the first t = 20 min
term of irradiation, the attenuation and relative change
in ultrasound velocity in a crystal are substantially re-
duced. An attentive analysis of the obtained results
showed that changes in these acoustic characteristics,
closely connected with increasing radiation dose, are
associated with a decrease in dislocation mobility due to
their stopping by point radiation defects. On the ground
of the obtained experimental data and the formula for
low-frequency measurements of the Granato-Lucke
theory, the absolute value of the damping factor of dis-
locations B and its behavior under the conditions of
changing the irradiation dose of the sample was deter-
mined in this paper. The comparison of the value B
with the analogous data found in special literature on
the high-frequency branch of a damped dislocation res-
onance was successfully performed. It was vividly
shown that these estimates of B found on different
branches of the frequency profile of dislocation reso-
nance differ by more than an order of magnitude.
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Статья поступила в редакцию 14.08.2018 г.
ИССЛЕДОВАНИЕ ВЛИЯНИЯ РЕНТГЕНОВСКОГО ОБЛУЧЕНИЯ
НА ПОДВИЖНОСТЬ ДИСЛОКАЦИЙ В КРИСТАЛЛАХ LiF
А.М. Петченко, Г.А. Петченко, С.Н. Бойко
Акустическим импульсным эхо-методом на частоте 7,5 МГц исследованы зависимости поглощения α и
относительной скорости ультразвука 0/ vv в монокристаллах LiF с остаточной деформацией = 0,65% при
300 К в интервале доз облучения 0…1057 P. Обнаружено, что увеличение дозы облучения приводит к за-
метному снижению затухания и относительной скорости ультразвука в образце вследствие уменьшения
20 ISSN 1562-6016. ВАНТ. 2018. 5(117)
эффективной длины дислокационного сегмента L при его закреплении радиационными центрами. На основе
результатов измерений акустических характеристик определено абсолютное значение величины коэффици-
ента демпфирования дислокаций В и проведено его сравнение с литературными данными, полученными по
высокочастотной ветви дислокационного резонанса.
ДОСЛІДЖЕННЯ ВПЛИВУ РЕНТГЕНІВСЬКОГО ОПРОМІНЕННЯ
НА РУХЛИВІСТЬ ДИСЛОКАЦІЙ В КРИСТАЛАХ LiF
О.М. Петченко, Г.О. Петченко, С.М. Бойко
Акустичним імпульсним ехо-методом на частоті 7,5 МГц досліджено залежності поглинання α і віднос-
ної швидкості ультразвуку 0/ vv у монокристалах LiF із залишковою деформацією = 0,65% при 300 К в
інтервалі доз опромінення 0…1057 P. Виявлено, що збільшення дози опромінення призводить до помітного
зниження згасання і відносної швидкості ультразвуку в зразку через зменшення ефективної довжини дисло-
каційного сегмента L при його закріпленні радіаційними центрами. На основі результатів вимірювань аку-
стичних характеристик визначено абсолютне значення величини коефіцієнта демпфування дислокацій В і
проведено його порівняння з літературними даними, одержаними за високочастотною гілкою дислокаційно-
го резонансу.
|
| id | nasplib_isofts_kiev_ua-123456789-147671 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T17:58:54Z |
| publishDate | 2018 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Petchenko, О.M. Petchenko, G.О. Boiko, S.M. 2019-02-15T17:40:55Z 2019-02-15T17:40:55Z 2018 Тhe investigation of X-rays irradiation effect on the mobility of dislocations in LiF crystals / О.M. Petchenko, G.О. Petchenko, S.M. Boiko // Вопросы атомной науки и техники. — 2018. — № 5. — С. 16-20. — Бібліогр.: 43 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/147671 539.67:539.374 An acoustic pulse echo method at a frequency of 7.5 MHz was used to study the dependence of the absorption α
 and the relative velocity of ultrasound Δv/v₀
 in single crystals of LiF with a residual deformation of ε = 0.65%, at
 300 K in the irradiation dose range 0...1057 R. It was found that an increase in the irradiation dose leads to a noticeable decrease in the damping and the relative ultrasound velocity in the sample as a result of a decrease in the effective density of the dislocation segment L when it is fixed by radiation centers. Based on the results of measurements
 of acoustic characteristics, the absolute value of the damping factor of dislocations B is determined and compared
 with the literature data obtained from the high-frequency branch of dislocation resonance. Акустичним імпульсним ехо-методом на частоті 7,5 МГц досліджено залежності поглинання α і відносної швидкості ультразвуку
 Δv/v₀ у монокристалах LiF із залишковою деформацією ε = 0,65% при 300 К в
 інтервалі доз опромінення 0…1057 P. Виявлено, що збільшення дози опромінення призводить до помітного
 зниження згасання і відносної швидкості ультразвуку в зразку через зменшення ефективної довжини дислокаційного сегмента L при його закріпленні радіаційними центрами. На основі результатів вимірювань акустичних характеристик визначено абсолютне значення величини коефіцієнта демпфування дислокацій В і
 проведено його порівняння з літературними даними, одержаними за високочастотною гілкою дислокаційного резонансу. Акустическим импульсным эхо-методом на частоте 7,5 МГц исследованы зависимости поглощения α и относительной скорости ультразвука Δv/v₀ в монокристаллах LiF с остаточной деформацией ε = 0,65% при 300 К в интервале доз облучения 0…1057 P. Обнаружено, что увеличение дозы облучения приводит к заметному снижению затухания и относительной скорости ультразвука в образце вследствие уменьшения эффективной длины дислокационного сегмента L при его закреплении радиационными центрами. На основе
 результатов измерений акустических характеристик определено абсолютное значение величины коэффициента демпфирования дислокаций В и проведено его сравнение с литературными данными, полученными по
 высокочастотной ветви дислокационного резонанса. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Физика радиационных повреждений и явлений в твердых телах Тhe investigation of X-rays irradiation effect on the mobility of dislocations in LiF crystals Дослідження впливу рентгенівського опромінення на рухливість дислокацій в кристалах LiF Исследование влияния рентгеновского облучения на подвижность дислокаций в кристаллах LiF Article published earlier |
| spellingShingle | Тhe investigation of X-rays irradiation effect on the mobility of dislocations in LiF crystals Petchenko, О.M. Petchenko, G.О. Boiko, S.M. Физика радиационных повреждений и явлений в твердых телах |
| title | Тhe investigation of X-rays irradiation effect on the mobility of dislocations in LiF crystals |
| title_alt | Дослідження впливу рентгенівського опромінення на рухливість дислокацій в кристалах LiF Исследование влияния рентгеновского облучения на подвижность дислокаций в кристаллах LiF |
| title_full | Тhe investigation of X-rays irradiation effect on the mobility of dislocations in LiF crystals |
| title_fullStr | Тhe investigation of X-rays irradiation effect on the mobility of dislocations in LiF crystals |
| title_full_unstemmed | Тhe investigation of X-rays irradiation effect on the mobility of dislocations in LiF crystals |
| title_short | Тhe investigation of X-rays irradiation effect on the mobility of dislocations in LiF crystals |
| title_sort | тhe investigation of x-rays irradiation effect on the mobility of dislocations in lif crystals |
| topic | Физика радиационных повреждений и явлений в твердых телах |
| topic_facet | Физика радиационных повреждений и явлений в твердых телах |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/147671 |
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