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Citation: Ananchenko, D.V.;
Nikiforov, S.V.; Sobyanin, K.V.;
Konev, S.F.; Dauletbekova, A.K.;
Akhmetova-Abdik, G.;
Akilbekov, A.T.; Popov, A.I.
Paramagnetic Defects and
Thermoluminescence in Irradiated
Nanostructured Monoclinic
Zirconium Dioxide. Materials 2022,
15, 8624. https://doi.org/10.3390/
ma15238624
Academic Editor: Carmen Canevali
Received: 4 October 2022
Accepted: 30 November 2022
Published: 2 December 2022
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materials
Article
Paramagnetic Defects and Thermoluminescence in Irradiated
Nanostructured Monoclinic Zirconium Dioxide
Daria V. Ananchenko 1, Sergey V. Nikiforov 1, Konstantin V. Sobyanin 1, Sergey F. Konev 1,
Alma K. Dauletbekova 2, Gulzhanat Akhmetova-Abdik 2, Abdirash T. Akilbekov 2and Anatoli I. Popov 3, *
1Department of Physics and Technology, Ural Federal University, Ekaterinburg 620002, Russia
2Department of Technical Physics, L.N. Gumilyov Eurasian National University, Astana 010000, Kazakhstan
3Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., LV-1063 Riga, Latvia
*Correspondence: popov@latnet.lv
Abstract:
The ESR spectra of nanostructured samples of monoclinic ZrO
2
irradiated by electrons
with energies of 130 keV, 10 MeV, and by a beam of Xe ions (220 MeV) have been studied. It has
been established that irradiation of samples with electrons (10 MeV) and ions leads to the formation
of radiation-induced F
+
centers in them. Thermal destruction of these centers is observed in the
temperature range of 375–550 K for electron-irradiated and 500–700 K for ion-irradiated samples. It is
shown that the decrease in the concentration of F
+
centers is associated with the emptying of traps
responsible for thermoluminescence (TL) peaks in the specified temperature range. In the samples
irradiated with an ion beam, previously unidentified paramagnetic centers with g = 1.963 and 1.986
were found, the formation of which is likely to involve Zr
3+
ions and oxygen vacancies. Thermal
destruction of these centers occurs in the temperature range from 500 to 873 K.
Keywords:
zirconium dioxide; ion irradiation; electron irradiation; paramagnetic defects; F
+
centers
1. Introduction
Zirconium dioxide is a wide-gap dielectric (Eg= 5–7 eV), which has high mechanical
(strength, refractoriness, corrosion resistance), as well as functional (transparency in a wide
range of wavelengths, high refractive index, high ionic conductivity) properties. These
properties determine the wide possibilities of using ZrO
2
in industry as a material for elec-
trochemical devices, and oxygen sensors [
1
–
4
], as well as materials for
photocatalysis [5–9]
and optical devices [
10
–
17
]. The optical and luminescent properties of this material are
largely determined by the presence of structural defects, which is especially important
when it is used in conditions of harsh radiation environments (nuclear power plants, space
electronics). Corpuscular radiation with a particle energy above the threshold (>0.3 MeV for
electrons) causes the formation of F-type centers (oxygen vacancies with trapped electrons)
in ZrO
2
and similar compounds by the impact mechanism [
18
–
21
]. It is known that these
defects have a significant effect on the optical and luminescent properties of binary and
complex wide-band gap oxide dielectrics [20–26].
One of the most sensitive methods for studying radiation-induced defects in materials
is electron spin resonance (ESR) spectroscopy. The main paramagnetic defects in ZrO
2
are centers associated with Zr
3+
ions (surface and bulk Zr
3+
,T-center) [
27
–
31
], oxygen
hole-centers or OHCs (O
−
centers) [
28
,
32
], and F-type (singly ionized oxygen vacancies
(F+) and divacancies (F2+)) [27,28,30,33].
Despite the sufficient number of publications on the topic of paramagnetic radiation
defects in ZrO
2
, their thermal properties remain insufficiently studied. The study of the
thermal stability of radiation defects is an important problem, since thermal annealing is a
way to eliminate defects and restore the performance characteristics of devices based on
ZrO
2
. The thermal decay of paramagnetic centers can be accompanied by the emission
of TL peaks. It is known that the TL curve of ZrO
2
irradiated with electrons contains two
Materials 2022,15, 8624. https://doi.org/10.3390/ma15238624 https://www.mdpi.com/journal/materials
Materials 2022,15, 8624 2 of 10
peaks at 400 and 500 K [
34
,
35
]. However, the relationship between these TL peaks and the
decay of radiation-induced paramagnetic defects in ZrO2remains unclear.
The study of the relationship between paramagnetic defects and TL properties of the
nanostructural modification of zirconium dioxide is of particular interest. It is known that
nanostructured materials have an increased resistance to the formation of radiation defects
in comparison with single-crystal analogs, and therefore they are promising materials for
high-dose (more than 10 Gy) luminescent dosimetry.
The purpose of this work is to identify paramagnetic defects in samples of monoclinic
nanostructured ZrO
2
irradiated with heavy ions and electrons of various energies and to
evaluate their thermal stability. It is important to note here that the thermal stability of
paramagnetic defects and their relationship to TL properties in monoclinic ZrO2 have not
been previously studied.
2. Materials and Methods
Samples in the form of tablets with a diameter of 5 mm and a thickness of 1 mm were
prepared by cold uniaxial pressing from a nanopowder with a nanoparticle size of
30–50 nm
provided by the Plasmotherm Company (Moscow, Russia). The nanopowder was produced
by plasma synthesis; ZrCl
4
was used as a raw material for its production. Characterization
of the pellets was carried out by the SEM method. The SEM image (Figure S1) and particle
size distribution (Figure S2) for ZrO
2
pellets are given in the Supplementary Materials. The
average particle size in the pellets, determined by the SEM method, corresponds to the one
declared by the manufacturer. The proportion of monoclinic ZrO
2
in the powder under
study, according to X-ray fluorescence data, was at least 99.02%; HfO
2
(0.331%), Cl (0.458%),
K
2
O (0.110%), TiO
2
(0.069%), PdO (0.009%), and Rb
2
O (0.006%) compounds were present
as impurities [36].
The studied samples were irradiated with three different types of radiation: (1) xenon
ions with an energy of 220 MeV at the DC-60 heavy ion accelerator (Nur-Sultan, Kaza-
khstan); (2) electrons with an energy of 130 keV from the pulsed electron accelerator
RADAN (pulse duration 2 ns, current density 60 A/cm
2
); (3) electrons with an energy of
10 MeV from the linear electron accelerator UELR (Yekaterinburg, Russia). Two types of
electron beams with different electron energies were used, since one of them (10 MeV) is ca-
pable of leading to the formation of new F-type radiation centers by the impact mechanism,
and the second (130 keV) only changes the charge states of existing defects or impurities.
The displacement energies for ZrO
2
under ion irradiation were estimated using the method
presented in [
37
,
38
]. Damage was modeled using the SRIM Pro 2013 software code [
39
]
with threshold displacement energies of 40 eV for both zirconium and oxygen atoms. For
fluences from 10
9
to 10
13
ion/cm
2
, the corresponding dpa values ranged from 0.5
×
10
−7
to 0.5
×
10
−3
dpa. Evaluation of dpa upon irradiation with 10 MeV electrons is carried
out according to the formula presented in [
40
]. The corresponding value of the atomic
displacement cross section was taken from [
41
]. According to the calculated value of the
displacements, the fluence of 1015 electrons/cm2is 1.3 ×10−6dpa.
TL was measured with a photomultiplier tube with a spectral sensitivity maximum at
400–420 nm under a linear heating rate of 2 ◦C/s.
ESR measurements were performed on a Bruker ELEXSYS 580 device with a resonant
frequency of 9.78 GHz in the range of the magnetic flux density change from 50 to 600 mT.
ESR spectra were recorded at room temperature after heating the samples in the range of
323–873 K with a step of 20 K. When studying the thermal stability of paramagnetic centers,
the samples were heated in the same mode as in the measurement of TL.
3. Results
To identify radiation-induced defects in ZrO
2
, the ESR spectra of the initial ZrO
2
pellets
irradiated with various radiation sources were measured (Figure 1). The ESR spectrum of
unirradiated ZrO
2
pellets contains a signal at a magnetic field B = 356.0 mT with
g = 1.965
and a peak-to-peak width 3.7 mT. This signal is associated with paramagnetic Zr
3+
ions,
Materials 2022,15, 8624 3 of 10
which were probably formed during the synthesis of the initial ZrO
2
nanopowders. The
ESR signal of Zr
3+
ions has already been detected earlier in unirradiated ZrO
2
[
27
,
42
]
and ZrO
2
:Er [
28
] nanopowders. The signal with g
⊥
= 1.975 and g
II
= 1.957–1.958 was
identified in them as bulk Zr
3+
. In [
28
,
29
], an ESR signal with identical g
⊥
but different
g
II
= 1.905–1.928 was assigned to surface Zr
3+
ions. The g factor of the paramagnetic Zr
3+
found by us in the initial pellets makes it possible to identify it as bulk Zr3+.
Materials 2022, 15, x FOR PEER REVIEW 3 of 11
3. Results
To identify radiation-induced defects in ZrO2, the ESR spectra of the initial ZrO2 pel-
lets irradiated with various radiation sources were measured (Figure 1). The ESR spec-
trum of unirradiated ZrO2 pellets contains a signal at a magnetic field B = 356.0 mT with
g = 1.965 and a peak-to-peak width 3.7 mT. This signal is associated with paramagnetic
Zr3+ ions, which were probably formed during the synthesis of the initial ZrO2 nanopow-
ders. The ESR signal of Zr3+ ions has already been detected earlier in unirradiated ZrO2
[27,42] and ZrO2:Er [28] nanopowders. The signal with g⊥ = 1.975 and gII = 1.957–1.958 was
identified in them as bulk Zr3+. In [28,29], an ESR signal with identical g⊥ but different gII=
1.905–1.928 was assigned to surface Zr3+ ions. The g factor of the paramagnetic Zr3+ found
by us in the initial pellets makes it possible to identify it as bulk Zr3+.
Figure 1. ESR spectra of unirradiated ZrO2 (1) and irradiated with an electron beam with an energy
of 130 keV (dose 15 kGy) (2), 10 MeV (fluence 1015 electrons/cm2) (3), and Xe ions with an energy of
220 MeV (fluence 1013 ions/cm2) (4).
In the ESR spectra of the samples irradiated with electrons with an energy of 130 keV
(a dose of 15 kGy), as in the initial pellets, there is a signal from Zr3+ with g = 1.965 and a
peak-to-peak width of 3.2 mT. In addition, a low-intensity signal with g = 1.999 appears.
This signal indicates the presence of a trace concentration of F+ centers in the irradiated
samples. Previously, the F+-center was detected in ZrO2 after electron and ion irradiation
and represented a line with a small g-factor anisotropy (g⊥ = 1.972 and gII = 1.996) [40].
Some authors report that the F+ center is characterized by an isotropic signal with a g-
factor near the free electron value (ge = 2.0023) [27,28]. Previously, the formation of F+ cen-
ters upon irradiation with an electron beam with an energy of 130 keV can occur because
of the capture of electrons by oxygen vacancies present in the initial samples, and in the
photoluminescence (PL) and pulsed cathodoluminescence (PCL) spectra of the samples
studied in this work. A luminescence band was observed at 480 nm, in which the for-
mation of oxygen vacancies participate [35].
Figure 1.
ESR spectra of unirradiated ZrO
2
(1) and irradiated with an electron beam with an energy
of 130 keV (dose 15 kGy) (2), 10 MeV (fluence 10
15
electrons/cm
2
) (3), and Xe ions with an energy of
220 MeV (fluence 1013 ions/cm2) (4).
In the ESR spectra of the samples irradiated with electrons with an energy of 130 keV
(a dose of 15 kGy), as in the initial pellets, there is a signal from Zr
3+
with g = 1.965 and a
peak-to-peak width of 3.2 mT. In addition, a low-intensity signal with g = 1.999 appears.
This signal indicates the presence of a trace concentration of F
+
centers in the irradiated
samples. Previously, the F
+
-center was detected in ZrO
2
after electron and ion irradiation
and represented a line with a small g-factor anisotropy (g
⊥
= 1.972 and g
II
= 1.996) [
40
].
Some authors report that the F
+
center is characterized by an isotropic signal with a g-factor
near the free electron value (g
e
= 2.0023) [
27
,
28
]. Previously, the formation of F
+
centers
upon irradiation with an electron beam with an energy of 130 keV can occur because of
the capture of electrons by oxygen vacancies present in the initial samples, and in the
photoluminescence (PL) and pulsed cathodoluminescence (PCL) spectra of the samples
studied in this work. A luminescence band was observed at 480 nm, in which the formation
of oxygen vacancies participate [35].
Irradiation of the pellets with electrons with an energy of 10 MeV (Figure 1) leads to
an increase in the intensity of the ESR signal with g = 1.999 (peak-to-peak width 2.7 mT)
from F
+
-centers. This indicates intensive processes of generation of these centers in ZrO
2
by the impact mechanism. It is known that the threshold energy for the formation of F-type
defects in ZrO
2
is about 1 MeV [
18
]; therefore, an electron energy of 10 MeV is sufficient
to displace oxygen atoms from the lattice sites. The intensity of the ESR signal of Zr
3+
in
Materials 2022,15, 8624 4 of 10
samples irradiated with electrons with an energy of 10 MeV is lower than in the initial
samples. Additional studies are required to elucidate the cause of this effect.
Irradiation of the investigated ZrO
2
samples with xenon ions with a fluence of up
to 10
13
ions/cm
2
did not lead to a change in the ESR spectrum compared to the initial
sample. The spectra of these pellets contain a Zr
3+
signal with g = 1.963 (peak-to-peak width
3.5 mT
). In samples irradiated with an ion beam with a fluence of 10
13
ions/cm
2
, the ESR
spectrum is significantly transformed, and the signal from Zr
3+
ions is no longer observed
in it (Figure 1). Instead, signals appear at 356.8 mT (g = 1.963), 350.0 mT (
g = 1.998
), and
352.5 mT (g = 1.986). The signal with g = 1.998 (peak-to-peak width 1.2 mT) is probably
associated with the presence F
+
centers in samples irradiated with ions. Signals with
g = 1.986 and 1.963 (peak-to-peak width 1.5 mT) can be attributed to a new previously
unidentified radiation-induced center.
It is well known that ion irradiation can quite often lead to material amorphization.
Previously, the authors of [
43
] found that the amorphization of nanocrystalline monoclinic
ZrO
2
is possible upon irradiation with uranium
238
U and Au ions with energies above 1 GeV,
when the energy losses exceed 40.2 keV/nm. It was shown in [
44
] that amorphization of
ZrO
2
irradiated with xenon ions with energies of 300–400 keV occurs at a peak displacement
damage level of about 680 dpa. We have estimated the appearance of an amorphous phase
in the studied ZrO
2
pellets upon irradiation with Xe ions of 220 MeV energy. To do this,
using the SRIM program, the values of electronic energy losses and displacement per
atom were calculated. The calculated value of electronic energy losses were found to be
19.8 keV/nm, which is less than the energy losses at which ZrO
2
amorphization begins.
The value of displacements for fluences from 10
9
to 10
13
ions/cm
2
was from 0.5
×
10
−7
to 0.5
×
10
−3
dpa, respectively, which is also significantly less than dpa, at which ZrO
2
amorphization was observed in [
44
]. Considering the above, we can conclude that in the
samples we studied, the formation of an amorphous phase is negligible.
The thermal stability of paramagnetic F
+
centers (g = 1.999) and Zr
3+
ions (g = 1.965)
in pellets irradiated with 10 MeV electrons was studied. Let us consider the temperature
dependence of the ESR intensity for the F
+
-center (Figure 2). The intensity of this signal
decreases at temperatures above 375 K. A sharp drop in intensity is observed in the tem-
perature range from 375 to 550 K. This temperature range coincides with the temperatures
at which TL is observed in the samples under study. Figure 2shows that the TL curve of
samples irradiated with 10 MeV electrons contains two TL peaks at 410 and 500 K. Since
the heating of the samples in the study of the thermal stability of paramagnetic centers and
the measurement of TL was carried out in the same mode, it can be concluded that the
change in the concentration of F
+
centers during heating can be associated with a change in
their charge state due to the capture of electrons released from the traps responsible for
TL. Previously, in [
35
], based on the results of studying the processes of TL quenching in
monoclinic ZrO2, the electronic nature of the TL peaks at 390 and 485 K was assumed.
The thermal stability of radiation-induced F
+
centers was studied in [
45
–
47
]. In a
parallel study of TL and ESR, the authors suggested that the monotonic decrease in the
concentration of F
+
-centers to 550–600 K may be due to its transition to the diamagnetic
state (Fcenter) as the result of the capture of an electron released from the trap. However,
two results contradicted this assumption. First, the temperature of the maximum found on
the TL curve (550 K) exceeded the temperature at which 50% of the F
+
-centers disappear
(450 K). Second, the calculated value of the trap depth responsible for the TL peak at
550 K
,
obtained by the initial rise method, was 0.7–1.1 eV, which is somewhat larger than the
defect annealing activation energy of 0.3–0.7 eV calculated from ESR data. The results
obtained by us (Figure 2) clearly indicate the relationship between the decrease in the
intensity of the ESR signal of F
+
-centers at T = 375–550 K and the emission of TL peaks
in the indicated temperature range, which confirms the assumption made by the authors
of [
45
–
47
]. It is well known that an alternative mechanism for annealing radiation-induced
F-type defects in oxides is the recombination of oxygen vacancies with interstitial oxygen,
the diffusion of which becomes possible when the crystal is heated [
48
–
50
]. Previously, the
Materials 2022,15, 8624 5 of 10
authors of [
51
] showed that in zirconium oxide irradiated with neutrons (E > 0.1 MeV), the
diffusion of interstitial oxygen becomes possible at temperatures above 500–600 K. In the
samples studied by us, a decrease in the concentration of F
+
centers is observed at lower
temperatures of 375–550 K, which testifies in favor of the proposed mechanism for the
destruction of F
+
centers associated with their ability to capture the charge carriers released
from traps that cause TL peaks.
Materials 2022, 15, x FOR PEER REVIEW 5 of 11
Figure 2. Dependence of the intensity of the ESR signal of F+-centers (1), Zr3+ ions (2) on the heating
temperature and TL (3) of ZrO2 irradiated with an electron beam with an energy of 10 MeV.
The thermal stability of radiation-induced F+ centers was studied in [45–47]. In a par-
allel study of TL and ESR, the authors suggested that the monotonic decrease in the con-
centration of F+-centers to 550–600 K may be due to its transition to the diamagnetic state
(F center) as the result of the capture of an electron released from the trap. However, two
results contradicted this assumption. First, the temperature of the maximum found on the
TL curve (550 K) exceeded the temperature at which 50% of the F+-centers disappear (450
K). Second, the calculated value of the trap depth responsible for the TL peak at 550 K,
obtained by the initial rise method, was 0.7–1.1 eV, which is somewhat larger than the
defect annealing activation energy of 0.3–0.7 eV calculated from ESR data. The results ob-
tained by us (Figure 2) clearly indicate the relationship between the decrease in the inten-
sity of the ESR signal of F+-centers at T = 375–550 K and the emission of TL peaks in the
indicated temperature range, which confirms the assumption made by the authors of [45–
47]. It is well known that an alternative mechanism for annealing radiation-induced F-
type defects in oxides is the recombination of oxygen vacancies with interstitial oxygen,
the diffusion of which becomes possible when the crystal is heated [48–50]. Previously,
the authors of [51] showed that in zirconium oxide irradiated with neutrons (E > 0.1 MeV),
the diffusion of interstitial oxygen becomes possible at temperatures above 500–600 K. In
the samples studied by us, a decrease in the concentration of F+ centers is observed at
lower temperatures of 375–550 K, which testifies in favor of the proposed mechanism for
the destruction of F+ centers associated with their ability to capture the charge carriers
released from traps that cause TL peaks.
It should also be noted that at temperatures of 550–700 K, the decrease in the concen-
tration of F+ centers slows down and a change in the shape of the ESR signal is observed
(Figure 3). More detailed studies have shown that at Т = 525–700 K, the g-factor of the F+-
center shifts from 1.998 to 1.995 (Figure 3 inset). The shift of the g-factor of the F+ center
may indicate a change in its local crystalline environment. This assumption can be sup-
ported by an increase in the ESR intensity of Zr3+ ions in the same temperature range. In
this case, the Zr3+ and ions can change the local environment of the F+ centers.
Figure 2.
Dependence of the intensity of the ESR signal of F
+
-centers (1), Zr
3+
ions (2) on the heating
temperature and TL (3) of ZrO2irradiated with an electron beam with an energy of 10 MeV.
It should also be noted that at temperatures of 550–700 K, the decrease in the concen-
tration of F
+
centers slows down and a change in the shape of the ESR signal is observed
(Figure 3). More detailed studies have shown that at T = 525–700 K, the g-factor of the
F
+
-center shifts from 1.998 to 1.995 (Figure 3inset). The shift of the g-factor of the F
+
center may indicate a change in its local crystalline environment. This assumption can be
supported by an increase in the ESR intensity of Zr
3+
ions in the same temperature range.
In this case, the Zr3+ and ions can change the local environment of the F+centers.
The thermal stability of Zr
3+
ions has also been studied. Figure 2shows that in the
temperature range of 280–525 K, the intensity of the ESR signal associated with Zr
3+
does
not change. With a further increase in temperature to 750 K, it increases by a factor of
8.7. At temperatures above 750 K, the signal intensity drops, but does not return to the
value characteristic of the irradiated sample. The change in the ESR intensity of Zr
3+
is not
associated with the emptying of traps in the material under study, since, according to our
experiments, no TL peaks were observed in the temperature range of 600–850 K. At the
same time, the values of its intensity did not exceed the background values caused by the
thermal radiation of the heating element.
An increase in the Zr
3+
concentration with an increase in the annealing temperature
was observed earlier in [
52
]. The authors associated it with the transformation of Zr
4+
ions into Zr
3+
caused by electron capture. In this case, the electron donors can be oxygen
vacancies that have captured one or two electrons, as well as O
−
ions if there is a deficiency
of positive charge in the cationic sites located near these ions. These processes can also
take place in the samples studied in this work, since they contain defects associated with
oxygen vacancies.
Materials 2022,15, 8624 6 of 10
Materials 2022, 15, x FOR PEER REVIEW 6 of 11
Figure 3. ESR spectra of a ZrO2 pellet irradiated with electrons with an energy of 10 MeV, and then
annealed at temperatures of 540 K (1) and 580 K (2).
The thermal stability of Zr3+ ions has also been studied. Figure 2 shows that in the
temperature range of 280–525 K, the intensity of the ESR signal associated with Zr3+ does
not change. With a further increase in temperature to 750 K, it increases by a factor of 8.7.
At temperatures above 750 K, the signal intensity drops, but does not return to the value
characteristic of the irradiated sample. The change in the ESR intensity of Zr3+ is not asso-
ciated with the emptying of traps in the material under study, since, according to our
experiments, no TL peaks were observed in the temperature range of 600–850 K. At the
same time, the values of its intensity did not exceed the background values caused by the
thermal radiation of the heating element.
An increase in the Zr3+ concentration with an increase in the annealing temperature
was observed earlier in [52]. The authors associated it with the transformation of Zr4+ ions
into Zr3+ caused by electron capture. In this case, the electron donors can be oxygen va-
cancies that have captured one or two electrons, as well as O2- ions if there is a deficiency
of positive charge in the cationic sites located near these ions. These processes can also
take place in the samples studied in this work, since they contain defects associated with
oxygen vacancies.
Next, we studied the thermal stability of ESR signals in samples irradiated with ions.
Figure 4 shows the dependence of the intensity of the ESR signal of F+ centers (g = 1.998)
on the heating temperature in ZrO2 samples irradiated with a xenon ion beam with a flu-
ence of 1013 ions/cm2. The intensity of this signal begins to decrease at temperatures above
500 K, which is 125 K more than in the samples irradiated with electrons. Further, the ESR
intensity of the F+-centers monotonically drops to 675 K. In contrast to samples irradiated
with electrons, the TL peak at 410 K in ion-irradiated samples has a low intensity. The
difference in the temperature at which the annealing of F+ centers begins in the samples
irradiated with ions and electrons can be due to the difference in the intensity of this peak.
Thermal emptying of the trap responsible for the low-intensity TL peak in ion-irradiated
samples does not significantly affect the concentration of F+ centers. The decrease in the
concentration of F+-centers in ion-irradiated samples begins when the trap responsible for
Figure 3.
ESR spectra of a ZrO
2
pellet irradiated with electrons with an energy of 10 MeV, and then
annealed at temperatures of 540 K (1) and 580 K (2).
Next, we studied the thermal stability of ESR signals in samples irradiated with ions.
Figure 4shows the dependence of the intensity of the ESR signal of F
+
centers (g = 1.998) on
the heating temperature in ZrO
2
samples irradiated with a xenon ion beam with a fluence
of 10
13
ions/cm
2
. The intensity of this signal begins to decrease at temperatures above
500 K
, which is 125 K more than in the samples irradiated with electrons. Further, the ESR
intensity of the F
+
-centers monotonically drops to 675 K. In contrast to samples irradiated
with electrons, the TL peak at 410 K in ion-irradiated samples has a low intensity. The
difference in the temperature at which the annealing of F
+
centers begins in the samples
irradiated with ions and electrons can be due to the difference in the intensity of this peak.
Thermal emptying of the trap responsible for the low-intensity TL peak in ion-irradiated
samples does not significantly affect the concentration of F
+
centers. The decrease in the
concentration of F
+
-centers in ion-irradiated samples begins when the trap responsible for
the intense TL peak at 500 K is empty. This fact confirms the assumption that the thermal
decay of F+centers is related to the TL properties of ZrO2.
The data in Figure 4show that the decrease in concentration F
+
centers in the tempera-
ture range of 500–700 K is replaced by its growth at higher heating temperatures, which
was not observed in the samples irradiated with electrons. The interval of increase in the
concentration of F
+
centers can also be related to the emptying of traps. The TL curve
of samples irradiated with ions, in addition to the peaks at 410 and 500 K observed after
electron irradiation, contains an additional peak of a complex shape at 550–750 K, which
can contain both electronic and hole components. In this case, the emptying of electron
traps will contribute to a decrease in the concentration of F
+
centers, while the emptying of
hole traps will contribute to their growth, which is observed at T > 700 K. An increase in
the concentration of F
+
centers upon the emptying of hole traps occurs as a result of the
capture of holes by Fcenters. A more thorough study of the TL properties at temperatures
above 725 K is required to prove this assumption; however, the measurement of TL at such
temperatures is hampered by instrumental limitations, as well as by the presence of an
intense thermal background of the heating element.
The thermal stability of paramagnetic signals of an unidentified nature with g = 1.986
and 1.963 (Figure 1) was also studied in pellets irradiated with xenon ions (Figure 5).
The temperature dependence of the ESR intensity of these two signals is identical and
Materials 2022,15, 8624 7 of 10
decreases monotonically to an undetectable level in the temperature range from 500 to
873 K
. The identity of the behavior of the signal intensities with g = 1.986 and 1.963 with a
change in the heating temperature shows that these signals refer to one paramagnetic center.
The nature of this center is probably associated with a complex defect, which includes
paramagnetic Zr
3+
ions and oxygen vacancies. The participation of Zr
3+
ions in defect
formation is indicated by the simultaneous disappearance of the ESR signal of these ions
and the appearance of signals with g = 1.986 and 1.963 in ZrO
2
in pellets irradiated with an
ion beam with a fluence of 10
13
ions/cm
2
. It is also known that when ZrO
2
is irradiated
with ions with an energy above the threshold, an intense generation of anion vacancies
occurs in it, which can also contribute to the formation of complex defects [
40
,
53
,
54
]. In the
past few years, a large number of such complex defects have been studied in detail in MgO,
Al2O3, and Gd3Ga5O12 crystals [55–60].
Materials 2022, 15, x FOR PEER REVIEW 7 of 11
the intense TL peak at 500 K is empty. This fact confirms the assumption that the thermal
decay of F+ centers is related to the TL properties of ZrO2.
Figure 4. Dependence of the intensity of the ESR signal of F+-centers on the heating temperature (1)
and TL (2) of ZrO2 samples irradiated with xenon ions.
The data in Figure 4 show that the decrease in concentration F+ centers in the temper-
ature range of 500–700 K is replaced by its growth at higher heating temperatures, which
was not observed in the samples irradiated with electrons. The interval of increase in the
concentration of F+ centers can also be related to the emptying of traps. The TL curve of
samples irradiated with ions, in addition to the peaks at 410 and 500 K observed after
electron irradiation, contains an additional peak of a complex shape at 550–750 K, which
can contain both electronic and hole components. In this case, the emptying of electron
traps will contribute to a decrease in the concentration of F+ centers, while the emptying
of hole traps will contribute to their growth, which is observed at T > 700 K. An increase
in the concentration of F+ centers upon the emptying of hole traps occurs as a result of the
capture of holes by F centers. A more thorough study of the TL properties at temperatures
above 725 K is required to prove this assumption; however, the measurement of TL at
such temperatures is hampered by instrumental limitations, as well as by the presence of
an intense thermal background of the heating element.
The thermal stability of paramagnetic signals of an unidentified nature with g = 1.986
and 1.963 (Figure 1) was also studied in pellets irradiated with xenon ions (Figure 5). The
temperature dependence of the ESR intensity of these two signals is identical and de-
creases monotonically to an undetectable level in the temperature range from 500 to 873
K. The identity of the behavior of the signal intensities with g = 1.986 and 1.963 with a
change in the heating temperature shows that these signals refer to one paramagnetic cen-
ter. The nature of this center is probably associated with a complex defect, which includes
paramagnetic Zr3+ ions and oxygen vacancies. The participation of Zr3+ ions in defect for-
mation is indicated by the simultaneous disappearance of the ESR signal of these ions and
the appearance of signals with g = 1.986 and 1.963 in ZrO2 in pellets irradiated with an ion
beam with a fluence of 1013 ions/cm2. It is also known that when ZrO2 is irradiated with
ions with an energy above the threshold, an intense generation of anion vacancies occurs
in it, which can also contribute to the formation of complex defects [40,53,54]. In the past
few years, a large number of such complex defects have been studied in detail in MgO,
Al2O3, and Gd3Ga5O12 crystals [55–60].
Figure 4.
Dependence of the intensity of the ESR signal of F
+
-centers on the heating temperature (1)
and TL (2) of ZrO2samples irradiated with xenon ions.
Materials 2022, 15, x FOR PEER REVIEW 8 of 11
Figure 5. Dependence of the intensity of ESR signals with g = 1.986 (1) and g = 1.963 (2) on the heating
temperature of ZrO2 samples irradiated with xenon ions.
4. Conclusions
1. The formation of radiation-induced F+ centers in nanostructured monoclinic ZrO2
pellets under irradiation with fast electrons (10 MeV, fluence 1015 ion/cm2) and Xe
ions (220 MeV, fluence 1013 ion/cm2) has been observed.
2. It was found that the decrease in the concentration of F+ centers upon thermal anneal-
ing is due to the emptying of traps responsible for TL.
3. However, the change in the ESR intensity of Zr3+ centers during thermal annealing
does not correlate with the TL of the studied material.
4. Furthermore, irradiation of ZrO2 with Xe ions with a fluence of 1013 ions/cm2 leads to
the appearance of new EPR signals with g = 1.963 and 1.986 being of an unknown
nature and stable up to Т= 873 K.
Supplementary Materials: The following supporting information can be downloaded at:
www.mdpi.com/xxx/s1, Figure S1 and Figure S2: “SEM and particle size distribution data”
Author Contributions: Conceptualization, S.V.N. and A.K.D.; methodology, D.V.A. and S.V.N.;
software, S.F.K.; validation, D.V.A., S.V.N., and A.K.D.; formal analysis, D.V.A. and K.V.S.; investi-
gation, D.V.A., S.V.N., K.V.S., and S.F.K.; resources, A.T.A.; data curation, G.A.-A.; writing—origi-
nal draft preparation, S.V.N. and A.K.D.; writing—review and editing, D.V.A., S.V.N., A.K.D., and
A.I.P.; visualization, D.V.A.; supervision, S.V.N. and A.K.D.; project administration, A.K.D.; fund-
ing acquisition, A.I.P. All authors have read and agreed to the published version of the manuscript.
Funding: The work was carried out under the grant of the Ministry of Education and Science of the
Republic of Kazakhstan AP09260057, “Luminescence and radiation resistance of synthesized under
different conditions micro- and nanostructured compacts and ceramics based on ZrO2”. The re-
search was partly (A.I.P.) performed at the Center of Excellence of the Institute of Solid State Physics,
University of Latvia, supported through European Union Horizon 2020 Framework Programme
H2020-WIDESPREAD-01-2016-2017-TeamingPhase2, under grant agreement No. 739508, project
CAMART2.
Institutional Review Board Statement: Not applicable.
Figure 5.
Dependence of the intensity of ESR signals with g = 1.986 (1) and g = 1.963 (2) on the heating
temperature of ZrO2samples irradiated with xenon ions.
Materials 2022,15, 8624 8 of 10
4. Conclusions
1.
The formation of radiation-induced F
+
centers in nanostructured monoclinic ZrO
2
pellets under irradiation with fast electrons (10 MeV, fluence 10
15
ion/cm
2
) and Xe
ions (220 MeV, fluence 1013 ion/cm2) has been observed.
2.
It was found that the decrease in the concentration of F
+
centers upon thermal anneal-
ing is due to the emptying of traps responsible for TL.
3.
However, the change in the ESR intensity of Zr
3+
centers during thermal annealing
does not correlate with the TL of the studied material.
4.
Furthermore, irradiation of ZrO2 with Xe ions with a fluence of 10
13
ions/cm
2
leads
to the appearance of new EPR signals with g = 1.963 and 1.986 being of an unknown
nature and stable up to T = 873 K.
Supplementary Materials:
The following supporting information can be downloaded at: https:
//www.mdpi.com/article/10.3390/ma15238624/s1, Figures S1 and S2: SEM and particle size distri-
bution data.
Author Contributions:
Conceptualization, S.V.N. and A.K.D.; methodology, D.V.A. and S.V.N.; soft-
ware, S.F.K.; validation, D.V.A., S.V.N. and A.K.D.; formal analysis, D.V.A. and K.V.S.; investigation,
D.V.A., S.V.N., K.V.S. and S.F.K.; resources, A.T.A.; data curation, G.A.-A.; writing—original draft
preparation, S.V.N. and A.K.D.; writing—review and editing, D.V.A., S.V.N., A.K.D. and A.I.P.; visual-
ization, D.V.A.; supervision, S.V.N. and A.K.D.; project administration, A.K.D.; funding acquisition,
A.I.P. All authors have read and agreed to the published version of the manuscript.
Funding:
The work was carried out under the grant of the Ministry of Education and Science of
the Republic of Kazakhstan AP09260057, “Luminescence and radiation resistance of synthesized
under different conditions micro- and nanostructured compacts and ceramics based on ZrO
2
”.
The research was partly (A.I.P.) performed at the Center of Excellence of the Institute of Solid
State Physics, University of Latvia, supported through European Union Horizon 2020 Framework
Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2, under grant agreement No. 739508,
project CAMART2.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement:
The data presented in this study are available on request from the
corresponding author. The data are not publicly available due to the ongoing research.
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
Qi, S.; Porotnikova, N.M.; Ananyev, M.V.; Kuzmin, A.V.; Eremin, V.A.; Pankratov, A.A.; Molchanova, N.G.; Reznitskikh, O.G.;
Farlenkov, A.S.; Vovkotrub, E.G.; et al. High-temperature glassy-ceramic sealants SiO
2
–Al
2
O
3
–BaO–MgO and SiO
2
–Al
2
O
3
–ZrO
2
–
CaO–Na2O for solid oxide electrochemical devices. Trans. Nonferr. Met. Soc. China 2016,26, 2916–2924. [CrossRef]
2.
Farlenkov, A.S.; Ananyev, M.V.; Eremin, V.A.; Porotnikova, N.M.; Kurumchin, E.K.; Melekh, B.T. Oxygen isotope exchange in
doped calcium and barium zirconates. Solid State Ion. 2016,290, 108–115. [CrossRef]
3.
Farlenkov, A.S.; Ananyev, M.V.; Eremin, V.A.; Porotnikova, N.M.; Kurumchin, E.K. Particle coarsening influence on oxygen
reduction in LSM–YSZ composite materials. Fuel Cells 2015,15, 131–139. [CrossRef]
4.
Anan’ev, M.V.; Bershitskaya, N.M.; Plaksin, S.V.; Kurumchin, E.K. Phase equilibriums, oxygen exchange kinetics and diffusion in
oxides CaZr1−xScxO3−x/2−δ.Russ. J. Electrochem. 2012,48, 879–886. [CrossRef]
5.
Alotaibi, M.R.M.; Mahmoud, M.H.H. Photocatalytic remediation of ciprofloxacin based on Fe
2
O
3
@ZrO
2
nanocomposites under
visible-light. Opt. Mater. 2022,124, 112041. [CrossRef]
6.
Alotaibi, M.R.; Mahmoud, M.H.H. Promptness of tetracycline pollutant degradation via CuCo
2
O
4
@ZrO
2
nanocomposites
photocatalyst. Opt. Mater. 2022,126, 112200. [CrossRef]
7.
Helmiyati, H.; Fitriana, N.; Chaerani, M.L.; Dini, F.W. Green hybrid photocatalyst containing cellulose and
γ
–Fe
2
O
3
–ZrO
2
heterojunction for improved visible-light driven degradation of Congo red. Opt. Mater. 2022,124, 111982. [CrossRef]
8. Majnis, M.F.; Yee, O.C.; Adnan, M.A.M.; Hamid, M.R.Y.; Shaari, K.Z.K.; Julkapli, N.M. Photoactive of Chitosan-ZrO2/TiO2thin
film in catalytic degradation of malachite green dyes by solar light. Opt. Mater. 2022,124, 111967. [CrossRef]
9.
Mekala, R.; Rajendran, V. Aqueous and organic media assisted Ce: ZrO
2
nanoparticles by precipitation and its structural,
morphological, optical, and catalytic activities. Opt. Mater. 2021,122, 111718. [CrossRef]
Materials 2022,15, 8624 9 of 10
10.
Ma, C.G.; Brik, M.G.; Kiisk, V.; Kangur, T.; Sildos, I. Spectroscopic and crystal-field analysis of energy levels of Eu
3+
in SnO
2
in
comparison with ZrO2and TiO2.J. Alloys Compd. 2011,509, 3441–3451. [CrossRef]
11.
´
Ciri´c, A.; Stojadinovi´c, S.; Drami´canin, M.D. Custom-built thermometry apparatus and luminescence intensity ratio thermometry
of ZrO2: Eu3+ and Nb2O5: Eu3+.Meas. Sci. Technol. 2019,30, 045001. [CrossRef]
12.
Sudhakar, P.; Reddy, A.S.S.; Zhydachevskyy, Y.; Suchocki, A.; Brik, M.G.; Kumar, V.R.; Piasecki, M.; Veeraiah, N. Luminescence
characteristics of Er
3+
ions in ZnO-Ta
2
O
5
/Nb
2
O
5
/ZrO
2
-B
2
O
3
glass system-A case study of energy transfer from ZnO to Er
3+
ions. Opt. Mater. 2018,86, 87–94. [CrossRef]
13.
Nashivochnikov, A.A.; Kostyukov, A.I.; Zhuzhgov, A.V.; Rakhmanova, M.I.; Cherepanova, S.V.; Snytnikov, V.N. Shaping the
photoluminescence spectrum of ZrO
2
: Eu
3+
phosphor in dependence on the Eu concentration. Opt. Mater.
2021
,121, 111620.
[CrossRef]
14.
Lauer, P.E.; Watson, B.H., III; Rai, A.K.; Qian, Z.; Wolfe, D.E. Material properties of IR-to-IR down-converting Er and Nd-Doped
ZrO2nanopowders. Opt. Mater. 2021,119, 111299. [CrossRef]
15.
Borik, M.; Kulebyakin, A.; Larina, N.; Lomonova, E.; Morozov, D.; Myzina, V.; Ryabochkina, P.; Tabachkova, N. Spectral-
Luminescent Properties of ZrO2-Y2O3-Pr2O3Crystals. Crystals 2022,12, 1103. [CrossRef]
16.
Yang, Y.; Xu, S.; Li, S.; Wu, W.; Pan, Y.; Wang, D.; Hong, X.; Cheng, Z.; Deng, W. Luminescence Properties of Ho
2
O
3
-Doped Y
2
O
3
Stabilized ZrO2Single Crystals. Crystals 2022,12, 415. [CrossRef]
17.
Hayakawa, T.; Ikeshita, R.; Duclère, J.R.; Lecomte, A. Simple Method to Estimate Fractional Numbers of Eu
3+
Ions in Different
Phases in Highly Luminescent ZrO2–SiO2Nanocomposites. Phys. Status Solidi B 2022,259, 2100560. [CrossRef]
18.
Costantini, J.M.; Beuneu, F. Threshold displacement energy in yttria-stabilized zirconia. Phys. Status Solidi C
2007
,4, 1258–1263.
[CrossRef]
19.
Smith, K.L.; Colella, M.; Cooper, R.; Vance, E.R. Measured displacement energies of oxygen ions in titanates and zirconates. J.
Nucl. Mater. 2003,321, 19–28. [CrossRef]
20.
Popov, A.I.; Kotomin, E.A.; Maier, J. Basic properties of the F-type centers in halides, oxides and perovskites. Nucl. Instrum.
Methods Phys. Res. Sect. B Beam Interact. Mater. At. 2010,268, 3084–3089. [CrossRef]
21.
Kotomin, E.A.; Popov, A.I. Radiation-induced point defects in simple oxides. Nucl. Instrum. Methods Phys. Res. Sect. B Beam
Interact. Mater. At. 1998,141, 1–15. [CrossRef]
22.
Zhukovskii, Y.F.; Pugno, N.; Popov, A.I.; Balasubramanian, C.; Bellucci, S. Influence of Fcentres on structural and electronic
properties of AlN single-walled nanotubes. J. Phys. Condens. Matter 2007,19, 395021. [CrossRef]
23.
González, R.; Monge, M.A.; Santiuste, J.M.; Pareja, R.; Chen, Y.; Kotomin, E.; Kukla, M.M.; Popov, A.I. Photoconversion of F-type
centers in thermochemically reduced MgO single crystals. Phys. Rev. B 1999,59, 4786. [CrossRef]
24.
Luchechko, A.; Vasyltsiv, V.; Kostyk, L.; Tsvetkova, O.; Popov, A.I. Shallow and deep trap levels in X-ray irradiated
β
-Ga
2
O
3
: Mg.
Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. At. 2019,441, 12–17. [CrossRef]
25.
Popov, A.I.; Lushchik, A.; Shablonin, E.; Vasil’chenko, E.; Kotomin, E.A.; Moskina, A.M.; Kuzovkov, V.N. Comparison of the
F-type center thermal annealing in heavy-ion and neutron irradiated Al
2
O
3
single crystals. Nucl. Instrum. Methods Phys. Res. Sect.
B Beam Interact. Mater. At. 2018,433, 93–97. [CrossRef]
26.
Ananchenko, D.V.; Nikiforov, S.V.; Kuzovkov, V.N.; Popov, A.I.; Ramazanova, G.R.; Batalov, R.I.; Bayazitov, R.M.; Novikov, H.A.
Radiation-induced defects in sapphire single crystals irradiated by a pulsed ion beam. Nucl. Instrum. Methods Phys. Res. Sect. B
Beam Interact. Mater. At. 2020,466, 1–7. [CrossRef]
27. Zhao, Q.; Wang, X.; Cai, T. The study of surface properties of ZrO2.Appl. Surf. Sci. 2004,225, 7–13. [CrossRef]
28.
Lokesha, H.S.; Chithambo, M. A combined study of the thermoluminescence and electron paramagnetic resonance of point
defects in ZrO2: Er3+.Radiat. Phys. Chem. 2020,172, 108767. [CrossRef]
29.
Gionco, C.; Paganini, M.C.; Giamello, E.; Burgess, R.; Di Valentin, C.; Pacchioni, G. Paramagnetic defects in polycrystalline
zirconia: An EPR and DFT study. Chem. Mater. 2013,25, 2243–2253. [CrossRef]
30.
Costantini, J.M.; Beuneu, F.; Gourier, D.; Trautmann, C.; Calas, G.; Toulemonde, M. Colour centre production in yttria-stabilized
zirconia by swift charged particle irradiations. J. Phys. Condens. Matter 2004,16, 3957. [CrossRef]
31.
Costantini, J.M.; Cavani, O.; Boizot, B. On-line optical absorption of electron-irradiated yttria-stabilized zirconia. J. Phys. Chem.
Solids 2022,169, 110853. [CrossRef]
32.
Orera, V.M.; Merino, R.I.; Chen, Y.; Cases, R.; Alonso, P.J. Intrinsic electron and hole defects in stabilized zirconia single crystals.
Phys. Rev. B 1990,42, 9782. [CrossRef] [PubMed]
33.
Costantini, J.M.; Ogawa, T.; Bhuian, A.S.I.; Yasuda, K. Cathodoluminescence induced in oxides by high-energy electrons: Effects
of beam flux, electron energy, and temperature. J. Lumin. 2019,208, 108–118. [CrossRef]
34.
Nikiforov, S.V.; Kortov, V.S.; Kazantseva, M.G.; Petrovykh, K.A. Luminescent properties of monoclinic zirconium oxide. J. Lumin.
2015,166, 111–116. [CrossRef]
35.
Nikiforov, S.V.; Kortov, V.S.; Savushkin, D.L.; Vokhmintsev, A.S.; Weinstein, I.A. Thermal quenching of luminescence in nanos-
tructured monoclinic zirconium dioxide. Radiat. Meas. 2017,106, 155–160. [CrossRef]
36.
Marfin, A.Y.; Nikiforov, S.V.; Ananchenko, D.V.; Zyryanov, S.S.; Yakovlev, G.A.; Denisov, E.I. Thermoluminescence of monoclinic
ZrO2after electron irradiation. AIP Conf. Proc. 2022,2466, 030012.
37.
Egeland, G.W.; Valdez, J.A.; Maloy, S.A.; McClellan, K.J.; Sickafus, K.E.; Bond, G.M. Heavy-ion irradiation defect accumulation in
ZrN characterized by TEM, GIXRD, nanoindentation, and helium desorption. J. Nucl. Mater. 2013,435, 77–87. [CrossRef]
Materials 2022,15, 8624 10 of 10
38.
Stoller, R.E.; Toloczko, M.B.; Was, G.S.; Certain, A.G.; Dwaraknath, S.; Garner, F.A. On the use of SRIM for computing radiation
damage exposure. Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. At. 2013,310, 75–80. [CrossRef]
39. Ziegler, J.F. SRIM. Available online: http://www.SRIM.org (accessed on 19 October 2022).
40.
Costantini, J.-M.; Beuneu, F.; Weber, W.J. Radiation damage in cubic-stabilized zirconia (ZrO
2-X
) and ceria (CeO
2-X
). In Properties
of Fluorite Structure Materials; Oak Ridge National Laboratory: Oak Ridge, TN, USA, 2013; pp. 127–151.
41.
Oen, O.S. Cross Sections for Atomic Displacements in Solids by Fast Electrons; No. ORNL-4897; Oak Ridge National Laboartory: Oak
Ridge, TN, USA, 1973.
42.
Nikiforov, S.V.; Menshenina, A.A.; Konev, S.F. The influence of intrinsic and impurity defects on the luminescent properties of
zirconia. J. Lumin. 2019,212, 219–226. [CrossRef]
43.
Lu, F.; Wang, J.; Lang, M.; Toulemonde, M.; Namavar, F.; Trautmann, C.; Zhang, J.; Ewing, R.C.; Lian, J. Amorphization of
nanocrystalline monoclinic ZrO2by swift heavy ion irradiation. Phys. Chem. Chem. Phys. 2012,14, 12295–12300. [CrossRef]
44.
Sickafus, K.E.; Matzke, H.; Yasuda, K.; Chodak, P., III; Verrall, R.A.; Lucuta, P.G.; Andrews, H.R.; Turos, A.; Fromknecht, R.; Baker,
N.P. Radiation damage effects in cubic-stabilized zirconia irradiated with 72 MeV I
+
ions. Nucl. Instrum. Methods Phys. Res. Sect.
B Beam Interact. Mater. At. 1998,141, 358–365. [CrossRef]
45.
Costantini, J.M.; Beuneu, F. Color center annealing and ageing in electron and ion-irradiated yttria-stabilized zirconia. Nucl.
Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. At. 2005,230, 251–256. [CrossRef]
46.
Costantini, J.M.; Beuneu, F. Thermal recovery of colour centres induced in cubic yttria-stabilized zirconia by charged particle
irradiations. J. Phys. Condens. Matter 2006,18, 3671. [CrossRef]
47.
Costantini, J.M.; Beuneu, F.; Fasoli, M.; Galli, A.; Vedda, A.; Martini, M. Thermo-stimulated luminescence of ion-irradiated
yttria-stabilized zirconia. J. Phys. Condens. Matter 2011,23, 115901. [CrossRef] [PubMed]
48.
Kotomin, E.; Kuzovkov, V.; Popov, A.I.; Maier, J.; Vila, R. Anomalous kinetics of diffusion-controlled defect annealing in irradiated
ionic solids. J. Phys. Chem. A 2018,122, 28–32. [CrossRef] [PubMed]
49.
Lushchik, A.; Kuzovkov, V.N.; Kotomin, E.A.; Prieditis, G.; Seeman, V.; Shablonin, E.; Vasil’chenko, E.; Popov, A.I. Evidence
for the formation of two types of oxygen interstitials in neutron-irradiated
α
-Al
2
O
3
single crystals. Sci. Rep.
2021
,11, 20909.
[CrossRef] [PubMed]
50.
Lushchik, A.; Seeman, V.; Shablonin, E.; Vasil’chenko, E.; Kuzovkov, V.N.; Kotomin, E.A.; Popov, A.I. Detection of hidden oxygen
interstitials in neutron-irradiated corundum crystals. Opt. Mater. X 2022,14, 100151. [CrossRef]
51.
Lushchik, A.; Kuzovkov, V.N.; Kudryavtseva, I.; Popov, A.I.; Seeman, V.; Shablonin, E.; Vasil’chenko, E.; Kotomin, E.A. The Two
Types of Oxygen Interstitials in Neutron-Irradiated Corundum Single Crystals: Joint Experimental and Theoretical Study. Phys.
Status Solidi B 2022,259, 2100317. [CrossRef]
52.
Savoini, B.; Caceres, D.; Vergara, I.; Gonzalez, R.; Santiuste, J.M. Radiation damage in neutron-irradiated yttria-stabilized-zirconia
single crystals. J. Nucl. Mater. 2000,277, 199–203. [CrossRef]
53.
Bykov, I.P.; Brik, A.B.; Bagmut, N.N.; Kalinichenko, A.M.; Bevz, V.V.; Vereshchak, V.G.; Yastrabik, L. Effect of annealing on ESR
characteristics of zirconia nanopowders with different impurity compositions. Phys. Solid State 2009,51, 1248–1253. [CrossRef]
54.
Costantini, J.M.; Trautmann, C.; Thome, L.; Jagielski, J.; Beuneu, F. Swift heavy ion-induced swelling and damage in yttria-
stabilized zirconia. J. Appl. Phys. 2007,101, 073501. [CrossRef]
55.
Shablonin, E.; Popov, A.I.; Prieditis, G.; Vasil’chenko, E.; Lushchik, A. Thermal annealing and transformation of dimer Fcenters
in neutron-irradiated Al2O3single crystals. J. Nucl. Mater. 2021,543, 152600. [CrossRef]
56.
Seeman, V.; Popov, A.I.; Shablonin, E.; Vasil’chenko, E.; Lushchik, A. EPR-active dimer centers with S=1 in
α
-Al
2
O
3
single crystals
irradiated by fast neutrons. J. Nucl. Mater. 2022,569, 153933. [CrossRef]
57.
Baubekova, G.; Akilbekov, A.; Popov, A.I.; Shablonin, E.; Vasil’chenko, E.; Zdorovets, M.; Lushchik, A. About complexity of the
2.16-eV absorption band in MgO crystals irradiated with swift Xe ions. Radiat. Meas. 2020,135, 106379. [CrossRef]
58.
Mironova-Ulmane, N.; Popov, A.I.; Antuzevics, A.; Krieke, G.; Elsts, E.; Vasil’chenko, E.; Sildos, I.; Puust, L.; Ubizskii, S.B.; Sugak,
D.; et al. EPR and optical spectroscopy of neutron-irradiated Gd
3
Ga
5
O
12
single crystals. Nucl. Instrum. Methods Phys. Res. Sect. B
Beam Interact. Mater. At. 2020,480, 22–26. [CrossRef]
59.
Mironova-Ulmane, N.; Sildos, I.; Vasil’chenko, E.; Chikvaidze, G.; Skvortsova, V.; Kareiva, A.; Muñoz-Santiuste, J.E.; Pareja,
R.; Elsts, E.; Popov, A.I. Optical absorption and Raman studies of neutron-irradiated Gd
3
Ga
5
O
12
single crystals. Nucl. Instrum.
Methods Phys. Res. Sect. B Beam Interact. Mater. At. 2018,435, 306–312. [CrossRef]
60.
Karipbayev, Z.T.; Kumarbekov, K.; Manika, I.; Dauletbekova, A.; Kozlovskiy, A.L.; Sugak, D.; Ubizskii, S.B.; Akilbekov, A.;
Suchikova, Y.; Popov, A.I. Optical, Structural, and Mechanical Properties of Gd
3
Ga
5
O
12
Single Crystals Irradiated with
84
Kr+
Ions. Phys. Status Dolidi B 2022,259, 2100415. [CrossRef]
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