Influence of sulfate ions on properties of co-precipitated Y 3Al5O12:Nd3+ nanopowders

Article abstract of DOI:10.1016/j.jallcom.2010.08.046

A new precursor of yttrium aluminum garnet with an approximate composition of NH₄AlY_0.6(CO₃)_x(OH) _y(SO₄)_z·nH₂O has been synthesized via a reverse strike co-precipitation method with ammonium hydrogen carbonate as the precipitant and ammonium aluminum sulfate as the sulfate ions source. The evolution of phase, chemical composition and morphology of the precursor during calcination has been studied by means of XRD, XPS, DTA-TG, BET methods and FT-IR spectroscopy. The loosely agglomerated powders with narrow size distribution, spherical shapes and diameter of 50-60 nm have been obtained by calcination of the sulfate-containing precursor at 1100 °C for 2 h. The doping by sulfate ions enhances densification of Y₃Al ₅O₁₂:Nd³⁺ nanopowders compared to undoped ones. This leads to improved microstructure and optical transmittance of vacuum sintered ceramics prepared from sulfate-doped nanopowders.

Full text of DOI:10.1016/j.jallcom.2010.08.046

Journal of Alloys and Compounds 508 (2010) 200–205
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Influence of sulfate ions on properties of co-precipitated Y3Al5O12:Nd3+
nanopowders
T.G. Deinekaa, A.G. Doroshenkoa, P.V. Mateychenkoa, A.V. Tolmacheva, E.A. Vovka, O.M. Vovka,
R.P. Yavetskiya,∗, V.N. Baumerb, D.S. Sofronovb
a Institute for Single Crystals, STC “Institute for Single Crystals”, NAS of Ukraine, 60 Lenin Ave., 61001 Kharkov, Ukraine
b SSI STC “Institute for Single Crystals” NAS of Ukraine, 60 Lenin Ave., 61001 Kharkov, Ukraine
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 May 2010
Received in revised form 3 August 2010
Accepted 4 August 2010
Available online 19 August 2010
A
new precursor of yttrium aluminum garnet with an approximate composition of
NH4AlY0.6(CO3)x(OH)y(SO4)z·nH2O has been synthesized via a reverse strike co-precipitation method
with ammonium hydrogen carbonate as the precipitant and ammonium aluminum sulfate as the sulfate
ions source. The evolution of phase, chemical composition and morphology of the precursor during
calcination has been studied by means of XRD, XPS, DTA–TG, BET methods and FT-IR spectroscopy.
The loosely agglomerated powders with narrow size distribution, spherical shapes and diameter of
50–60 nm have been obtained by calcination of the sulfate-containing precursor at 1100 ◦C for 2 h. The
doping by sulfate ions enhances densification of Y3Al5O12:Nd3+ nanopowders compared to undoped
ones. This leads to improved microstructure and optical transmittance of vacuum sintered ceramics
prepared from sulfate-doped nanopowders.
Keywords:
YAG
Co-precipitation
Dispersant
Optical ceramics
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
on chemical composition and physico-chemical properties of the
precursor. Co-precipitation with ammonium hydrogen carbonate
Synthesis of well-dispersed nanocrystalline powders is a key
factor in advanced technologies of transparent ceramics fabrica-
tion. Nanopowders provide more homogenous particle packing
during molding and densify into transparent bodies without
applying a pressure at lower temperatures compared to con-
ventional micron-sized powders. To produce highly transparent
ceramics which optical and laser characteristics are compara-
ble with corresponding single crystals the initial nanopowders
should meet following requirements: low agglomeration degree,
spherical shape, ultrafine particle size (near 100 nm) and narrow
size distribution [1,2]. Nowadays relatively simple wet chemical
methods are widely used to synthesize oxide nanopowders of
multication compounds due to excellent mixing of starting mate-
rials and homogeneity of final product at the molecular level.
For instance, co-precipitation from water solutions with subse-
quent calcination of amorphous precipitant to convert it into
crystalline phase is considered as one of the most promising
methods to produce Y3Al5O12 (YAG) nanopowders ([3–7] and ref-
erences therein). Sinterability of nanopowders heavily depends
(AHC) usually leads to formation of carbonate precursors, which
decompose at low temperatures and possess only loose agglom-
eration. The favorable morphological features of precursors are
responsible for creation of low agglomerated oxide nanopow-
ders by calcination. The advantages of carbonate precursors for
production of highly sinterable nanopowders were disclosed for
rare earth sesquioxides and YAG. In [6] it was shown that YAG
nanopowders obtained from carbonate precursor with composi-
tion of NH4AlY0.6(CO3)x(OH)y·nH2O densify more homogenously
and achieve higher density after vacuum sintering compared to
the powders obtained from hydroxide precursor. At the same
time, even low residual agglomeration of carbonate-derived YAG
nanopowders impedes formation of transparent ceramics appre-
ciably and requires additional technological treatment of resulting
nanopowders, such as special drying, wet or dry high-energy ball
milling, etc. For this reason so-called “design” of nanopowders is an
extremely important challenge of advanced powder technologies.
The control of morphological and physico-chemical proper-
ties of oxide nanopowders can be achieved via utilization of
additives modifying in some way the charge state of particle sur-
faces. The purpose of modification is to provide formation of
double charged layer on the surface of each particle and, conse-
quently, to increase the repulsion forces between the particles and
prevent their agglomeration. Recently it was shown that introduc-
tion of sulfate ions into reaction mixture allows one to produce
∗
Corresponding author at: Institute for Single Crystals, STC “Institute for Single
Crystals”, NAS of Ukraine, Department of Complex Crystalline Materials, 60 Lenin
Ave., 61001 Kharkov, Ukraine. Tel.: +380 57 341 0415; fax: +380 57 340 9343.
E-mail address: yavetskiy@isc.kharkov.ua (R.P. Yavetskiy).
0925-8388/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2010.08.046

T.G. Deineka et al. / Journal of Alloys and Compounds 508 (2010) 200–205
201
low agglomerated Al2O3 [8], Sc2O3 [1] and Y2O3 [9–11] pow-
3. Results and discussion
ders with spherical morphology. It was reported that sulfate ions
promote formation of monodisperse spherical nanosized pow-
ders and hinder them from agglomeration. The doping by the
sulfate ions can be realized in several ways when ammonium
sulfate (NH4)2SO4 is used as sulfate ions source. (NH4)2SO4 can
be added into reaction mixture during precipitation [3–5], during
aging [10,11], or resulting precipitant can be rinsed by (NH4)2SO4
solution [9]. The addition of the ammonium sulfate directly into
reaction mixture gives rise to local change of mixture pH value
and consequently to local variations of chemical composition of
resulted powders [5]. The introduction of sulfate ions during aging
or by precipitant rinsing by (NH4)2SO4 solution does not permit
to control the concentration of sulfates in the precursor. In the
present work we use double crystallized aluminum ammonium
sulfate Al(NH4)(SO4)2·12H2O as the aluminum and sulfate ions
sources.
The studies of the sulfate ions influence on nanopowders prop-
erties are mainly done on rare earth sesquioxides Sc2O3 and Y2O3.
Despite some works report that doping by sulfate ions improves
structural and morphological characteristics of YAG nanopowders
[2,5,12,13], the role of sulfate ions in the production of highly sin-
terable YAG nanopowders is not clear. The purpose of this work is to
study the influence of sulfate ions on the morphology, size, agglom-
eration degree and sintering peculiarities of carbonate-derived YAG
nanopowders.
3.1. The effect of precipitant
Co-precipitation of inorganic mother salts by AHC leads to the
following hydrolysis reaction of AHC [6]:
NH4HCO3 + H2O ⇔ NH4OH + H2CO3
NH4OH ⇔ NH4+ + OH−
(1)
(2)
H2CO3 ⇔ H+ + HCO3−
(3)
(4)
HCO3− ⇔ H+ + CO3
2−
According to Eqs. (1)–(4), OH− and CO3
anions act as the
2−
precipitating ions. Thus, the chemical composition of a formed
precursor is a result of completion between these anions and
metal cations (Y3+, Al3+) during precipitation. As one can see, the
obtained precursor is usually a carbonate compound, which is only
softly agglomerated and has low decomposition temperature. It
is known that precipitation of Al3+ by AHC leads to formation of
AlOOH or NH4Al(OH2)CO3, whereas interaction of Y3+ with AHC
results in formation of normal or basic carbonates of Y2(CO3)3·nH2O
or Y(OH)CO3, correspondingly. The aluminum rich precursor is
formed first and is then coated by yttrium enriched particles during
precipitation process. For this reason precise control of the pre-
cipitation parameters is required to obtain YAG nanopowders of
2. Experimental
2−
stoichiometric composition. The SO4 ions have drastic effect on
2.1. Synthesis
precursor composition due to their strong tendency to form com-
2−
plexes. The influence of SO4
on the precursor composition and
YAG:Nd3+ nanopowders (3 at.%) were produced by
a reverse strike co-
YAG nanopowders properties is presented below.
precipitation method. The yttrium and neodymium nitrates were used as starting
materials. The ammonium aluminum sulfate Al(NH4)(SO4)2·12H2O (special purity
grade) was utilized as the aluminum and sulfate ions source. Nitrates were
prepared by dissolving of Y2O3 and Nd2O3 (both of special purity grade) in
concentrated nitric acid with subsequent evaporation of acid excess. The 1 M
ammonium hydrogen carbonate NH4HCO3 was used as a precipitant. The con-
centrations of Y(NO3)3, Nd(NO3)3 and Al(NH4)(SO4)2·12H2O solutions were 0.5 M.
The precipitation was carried out at the room temperature; the drip rate was
2 ml/min. The resultant suspension was aged for 24 h and then filtered via suction
filtration. After repeated washing with ethanol and deionized water the precipi-
tant was dried at 100 ◦C for 24 h. YAG:Nd3+ nanopowders of different dispersion
were obtained by precursor calcination in 900–1300 ◦C temperature range for
2 h in the air atmosphere. YAG:Nd3+ nanopowders for vacuum sintering were
molded by uniaxial pressing method with a pressure of 200 MPa. The sintering
of green bodies was performed using vacuum furnace with tungsten heating ele-
ments at the temperature of 1800 ◦C and vacuum of 10−3 Pa without sintering
aids.
3.2. DTA–TG analysis
The thermal decomposition curves of YAG:Nd3+ precursor are
given in Fig. 1. Continuous mass loss of the sample is observed
up to 1200 ◦C and is accompanied by total weight loss of 54%.
Three steps can be distinguished on the thermogravimetric curve
in 20–200, 200–900 and 900–1200 ◦C temperature ranges, indicat-
ing step-wise decomposition of the precursor. The most intensive
weight loss of 31% is observed at the first stage, following by two
relatively sloping stages. The corresponding mass losses are 17 and
6%. The ignition loss observed up to 200 ◦C is caused mainly by
removal of molecular and hydrated water. In the temperature range
of 200–900 ◦C the dehydroxylization and carbonate decomposition
occur, while desulfurization takes place up to 1200 ◦C. The exother-
mic effect on the DTA curve at 900–1000 ◦C was assigned to garnet
phase formation.
2.2. Characterization
Differential thermal and thermogravimetrical analyses of precursor were car-
ried out using a MOM Q-1500D derivatograph (Hungary). The heating rate was
10 ◦C/min, the alpha alumina was used as a reference. For thermal analysis the
precursor was dried at the room temperature. Fourier transform infrared (FT-IR)
spectra of the samples were measured on a FT-IR spectrometer SPECTRUM ONE
(PerkinElmer) with the KBr pellet. Phase identification was performed via X-ray
diffraction (XRD) method with a SIEMENS D-500 X-ray diffractometer using nickel
filtered Cu K˛ radiation. The phases were identified using “PDF-4” card file and “EVA”
retrieval system, included in the diffractometer software. Specific surface area of the
powders was determined by BET (Brunauer–Emmett–Teller) method. Morphology
of the powders was observed by a transmission electronic microscope TEM-125
operated at 100 kV accelerating voltage. Before microscopic examination, the pow-
ders were subjected to ultrasonication by using an ultrasonic dispergator UZDN-A at
frequency of 22 kHz for 45 s. The distilled water was used as a working medium. The
sulfur content was determined by X-ray photoelectron spectroscopy (XPS) method
by a XSAM-800 Kratos spectrometer using Mg K˛ radiation, and by electron probe
microanalysis using a Jeol JSM-6390LV (Jeol) scanning electron microscope with
INCA 350 microanalysis system. The density of ceramic samples was determined by
Archimedes method. The microstructure of ceramics was observed by a Jeol JSM-
6390LV (Jeol) scanning electron microscope after thermal etching at T = 1500 ◦C for
2 h.
Fig. 1. DTA and TG curves of the precursor.

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T.G. Deineka et al. / Journal of Alloys and Compounds 508 (2010) 200–205
to nanopowders desulfurization indicating that precursor contains
sulfate ions. The concentration of sulfate ions was determined by
XPS and electron probe microanalysis methods. According to elec-
tron probe microanalysis the precursor contains 2.7 at.% of sulfur.
The calcination temperature increase from 900 to 1100 ◦C results
in sulfur concentrations decrease from 1.13 to 0.16 at.%. The final
removal of sulfate ions (below the analyzer sensitivity limit of
0.1 at.%) occurs after powders calcination at 1200 ◦C. The XPS data
2−
evidences, that sulfur ions form SO4 anions in the precursor as
well as in calcined YAG nanopowders, since bonding energy value
of sulfur 2s-shell (232.3 eV) corresponds to well-known data for
MeSO4 compounds. Hence the new precursor with approximately
composition of NH4AlY0.6(CO3)x(OH)y(SO4)z·nH2O was obtained by
co-precipitation method. Formation of precursors containing sul-
fate ions by wet chemical methods was also reported in [5].
3.5. XRD analysis
Fig. 2. FT-IR spectra of precursor (1) and YAG:Nd3+ nanopowders calcined at 900 ◦
C
Evolution of the precursor phase composition during calcination
is given in Fig. 3. The initial precursor as well as the powders cal-
(2); 1000 ◦C (3); 1100 ◦C (4); 1200 ◦C (5) and 1300 ◦C (6).
3.3. FT-IR spectra
FT-IR spectra of precursor and its calcination products are
presented in Fig. 2. The wide structureless band with a max-
imum at 3435 cm−1 corresponds to absorption of molecular
water (∼3200–3500 cm−1
) as well as free hydroxyl groups
(∼3200–3500 cm−1) [14]. The broad peak at ∼1640 cm−1 is char-
acteristic to H–O–H bending mode of molecular water. The strong
absorption bands in 975–1230 cm−1 range correspond to SO4
.
2−
2−
It is known that SO4 ions demonstrate characteristic absorption
bands in the 1040–1210 cm−1 range and the range may be extended
if the bands are split [14]. The intense peaks at 520 and 1385 cm−1
indicate the presence of residual NH4+ and NO3− groups in the pre-
cursor [13]. The wide absorption bands at 1520 and 1410 cm−1 were
assigned to asymmetric stretch of C–O band in CO32−, while the
peak at 845 cm−1 was attributed to deformational vibration of C–O
in CO32−, respectively. Calcination of precursor at T = 900 ◦C sig-
nificantly decreases the band intensities of molecular water, free
hydroxyls and carbonate groups, but does not influence those of
sulfate ions (Fig. 2). Thus, at the temperatures up to 900 ◦C grad-
ual dehydration and carbonate decomposition mainly occur, while
desulfurization takes place at higher temperatures. The sample
calcined at T = 900 ◦C demonstrates the characteristic absorption
bands in 400–800 cm−1 wavelength range, corresponding to Y–O,
Al–O and Y–Al–O stretching vibrations [13,15]. This indicates the
formation of garnet phase after final precursor decarbonization.
The violent desulfurization of nanopowders occurs in 900–1200 ◦C
temperature range in good agreement with DTA–TG data (Fig. 1).
The complete removal of sulfate ions registered after calcination
at 1300 ◦C, is accompanied by disappearing of absorption bands
in 1040–1210 cm−1 range. The weak residual absorption peaks in
the calcined samples (1300 ◦C) are connected probably with H2O
adsorbed onto powder surface in the air.
3.4. Precursor composition
Co-precipitation of yttrium and aluminum nitrates by AHC
results in formation of complex precursor with the approximate
composition of NH4AlY0.6(CO3)x(OH)y·nH2O [6,12]. Our DTA data
(Fig. 1) agree well with that reported for carbonate precursor
[6,7]. However, TG shows that our precursor has higher decom-
position temperature (the observed difference is of about 200 ◦C).
Usually sulfate-doped precipitates demonstrate higher thermal
stability compared to undoped ones [1]. According to FT-IR data
the mass loss in the temperature range of 900–1200 ◦C corresponds
Fig. 3. XRD spectra of YAG:Nd3+ nanopowders calcined at 500 ◦C (1); 800 ◦C (2);
900 ◦C (3); 1000 ◦C (4) and 1100 ◦C (5).

T.G. Deineka et al. / Journal of Alloys and Compounds 508 (2010) 200–205
203
Fig. 4. The morphology of the precursor (1) and YAG:Nd3+ nanopowders calcined at T = 900 ◦C (2); T = 1100 ◦C (3); T = 1200 ◦C (4) and T = 1300 ◦C (5).
cined below 900 ◦C was amorphous. YAG phase formation occurs at
T = 900 ◦C. The powders calcined at 900 ◦C and above this tempera-
ture are single-phase since all diffraction peaks correspond to YAG
crystal lattice (Fig. 3). The formation temperature of garnet phase
during NH4AlY0.6(CO3)x(OH)y(SO4)z·nH2O precursor thermolysis is
in accordance with that for carbonate precursor [6,7], thus sul-
fate ions do not influence the phase formation temperatures and
their sequence. As the calcination temperature rises, the diffrac-
tion peaks become more and more intense and narrow, evidencing
the average crystallite size increase. However, this increase is very
weak (Fig. 3), indicating that sulfate ions slow down the diffusion
mass transport.
FT-IR, TG and electron probe microanalysis show that YAG
desulfurization occurs till the temperature of 1300 ◦C, while single-
phase YAG forms after calcination at T = 900 ◦C. According to XPS
data residual sulfate ions create SO42− anions, so YAG powders are
doped by SO42−-ions in 900–1300 ◦C temperature range. We sup-
pose two possibilities of such a doping. First, SO42−-ions can be
a part of impurity phases like Y2(SO4)3, Y2O2SO4 or Al2(SO4)3 in
the concentration below the XRD detection limit (1 mass%). Sec-
2−
crystal, SO4 entering into the particle volume is highly unlikely.
2−
So we suppose that SO4
nanoparticles surface.
in YAG nanopowders is placed at the
3.6. Powder morphology
The morphology of precursor and YAG:Nd3+ nanocrystalline
powders is shown in Fig. 4. The precursor consists of spherical
well-dispersed particles with an average diameter of 10–30 nm.
Sulfate ions adsorbed onto the precursor surface form double
electric layer (electric stabilization), which increases repulsion
forces between the particles and improves precursor dispersion.
YAG:Nd3+ nanoparticles obtained by precursor calcination inherit
ondly, since YAG nanopowders have high specific surface area,
2−
SO4
can enter into surface layers of YAG lattice. For beryllium
oxide obtained by thermal decomposition of beryllium sulfate it
2−
was shown, that residual SO4
ions can be located in the bulk
or the surface layers of BeO prior to dissociation [16]. Since the
Fig. 5. YAG:Nd3+ (3 at.%) ceramics obtained by vacuum sintering at 1800 ◦C for 10 h
using sulfate-doped (1) or undoped (2) nanopowders calcined at T = 1100 ◦C for 2 h.
The samples thickness is 1 mm.
2−
˚
radius of SO4 anion (∼2.3 A) [17] is much higher than that for oxy-
˚
gen ion (1.24 A), and assuming that every nanoparticle is a single

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T.G. Deineka et al. / Journal of Alloys and Compounds 508 (2010) 200–205
Fig. 6. SEM micrograph of surfaces of YAG:Nd3+ (3 at.%) ceramics, obtained by vacuum sintering of sulfate ions doped (1) and undoped (2) nanopowders calcined at T = 1100 ◦
C
for 2 h.
the morphology of precursor (memory shape effect). For instance,
calcination at 1100 ◦C for 2 h leads to creation of well-dispersed
uniform spherical particles of 50–60 nm in diameter (Fig. 4, 2).
The particle diameter calculated by BET method (60 nm) perfectly
matches with that determined by TEM, indicating low agglomera-
tion degree of the powders. The calcination temperature increase
results in formation of contact necks between some of the parti-
cles while the spherical morphology remains unaltered (Fig. 4, 3).
Further temperature increase up to 1300 ◦C results in inconvertible
morphology changes. Along with average particle size increase the
formation of coral-like hard aggregates occurs as a consequence
of significant rise of diffusion mass transport (Fig. 4, 4). It should
be noted that morphology of YAG particles correlates with their
calcination temperature (or with concentration of residual sulfate
ions). Only nanopowders containing more than 0.1 at.% of sulfate
ions demonstrate spherical morphology of particles.
Despite non-optimized compaction and sintering conditions, both
powders densify into translucent YAG:Nd3+ ceramics – the text can
be read through the 1 mm thick samples. Fig. 5 shows that ceramics
obtained with sulfate-doped YAG:Nd3+ nanopowders have better
optical transmittance compared to that prepared from undoped
powders. This fact arises from the better dispersion of sulfate ions
doped YAG nanopowders.
The microstructure of YAG:Nd3+ ceramics obtained using
sulfate-doped and undoped nanopowders is given in Fig. 6.
The samples have equal crystallite sizes of 10–15 mkm as
determined by the linear intercept method from 100 randomly
selected grains. The only difference between two samples is lower
porosity of the ceramics obtained using sulfate-doped precursor
of NH4AlY0.6(CO3)x(OH)y(SO4)z·nH2O composition (Fig. 6.1). The
numerous literature data suggest that sulfate ions influence sinter-
ing process via more homogenous densification of nanopowders,
as well as via more complete pore removal [10,11]. This leads to
improved structural and morphological characteristics of ceramics
and higher transparency (Fig. 5,6). Thus sulfate ions affect not only
morphology of nanopowders, but also their sinterability. Obviously,
some residual sulfate ions can survive in ceramics after vacuum sin-
tering. However their concentration is below detection limit of XPS
and electron probe microanalysis methods. One can suppose that
residual SO42− form liquid phase during sintering, accelerating for-
mation of pore free ceramics, as it was reported for Y2O3 [11]. But
to confirm this hypothesis additional research is needed. Obtaining
the transparent ceramics without any sintering aids is a purpose of
our further studies.
The doping by sulfate ions is favorable for the spherical
morphology and excellent dispersion of precursor and calcined
YAG:Nd3+ nanopowders. First, the free SO42−-ions act as
a
much stronger coagulant compared to NO3−-ions, probably, due
to higher valence state [1]. This leads to production of well-
dispersed precursor. Moreover, the residual sulfate ions can reduce
crystal anisotropy among crystal planes of YAG:Nd3+ during
calcination, as recently was observed for Y2O3 [10,11]. This pro-
vides equal growth rate of different crystallographic planes of
YAG:Nd3+ during recrystallization leading to near monodisperse
particle size distribution. The increase of decomposition tem-
perature of sulfate-containing precursor results in decrease of
diffusion mass transport between the particles, improving their
dispersion.
4. Conclusions
3.7. Sintering of YAG:Nd3+ nanopowders
The new Y3Al5O12 precursor with an approximate composi-
tion of NH4AlY0.6(CO3)x(OH)y(SO4)z·nH2O has been synthesized by
the co-precipitation method using ammonium hydrogen carbonate
as the precipitant and aluminum ammonium sulfate as the sul-
fate ions source. The influence of sulfate ions on the morphology,
dispersion and sinterability of Y3Al5O12:Nd3+ nanopowders cal-
cined in 800–1200 ◦C temperature range has been studied. It has
been shown that sulfate ions adsorbed onto the particles surface
form double electric layer, which increases interparticle repulsion
forces and improves precursor dispersion. The calcination of the
precursor at 1100 ◦C for 2 h result in formation of Y3Al5O12:Nd3+
near monodisperse spherical particles of 50–60 nm in diameter
possessing only lose agglomeration. Y3Al5O12:Nd3+ nanopowders
prepared from sulfate-containing precursor have better sinter-
ability compared with conventional carbonate-derived powders
therefore Y3Al5O12:Nd3+ vacuum sintered ceramics demonstrates
higher transmittance and lower residual porosity.
It is known that microstructure and optical transmittance of sin-
tered ceramics is highly influenced by the nanopowders properties,
namely average particle size, morphology, particle size distribu-
tion and agglomeration degree. The effect of sulfate ions doping
on sintering of YAG:Nd3+ nanopowders was studied via compari-
son of morphological and optical characteristics of vacuum sintered
ceramics. The vacuum sintering was conducted at 1800 ◦C for 10 h
using furnace equipped with tungsten heaters. Undoped YAG:Nd3+
nanopowders obtained according to [7] were used for purposes
of comparison. Both powders were calcined at T = 1100 ◦C during
2 h and compacted in one batch by cold uniaxial pressing method.
The densities of obtained green bodies were ranged within 45–50%
limit. The polished samples of ceramics obtained using sulfate-
doped and undoped YAG:Nd3+ nanopowders are presented in Fig. 5.
The densities of ceramics were 99.8–99.9% after vacuum sintering.

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205
Acknowledgments
[6] J.-G. Li, T. Ikegami, J. Lee, T. Mori, Y. Yajima, J. Eur. Ceram. Soc. 20 (2000)
2395–2405.
[7] V.N. Baumer, E.A. Vovk, O.M. Vovk, T.G. Deineka, M.B. Kosmyna, P.V. Matey-
chenko, V.M. Puzikov, Z.P. Sergienko, A.V. Tolmachev, A.N. Shekhovtsov, R.P.
Yavetskiy, Funct. Mater. 15 (2008) 540–545.
[8] M.D. Sacks, T.-Y. Tseng, S.Y. Lee, Ceram. Bull. 63 (1984) 301–310.
[9] N. Saito, Shin-ichi Matsuda, T. Ikegami, J. Am. Ceram. Soc. 81 (1998) 2023–2028.
[10] T. Ikegami, T. Mori, Y. Yajima, S. Takenouchi, T. Misawa, Y. Moriyoshi, J. Ceram.
Soc. Jpn. 107 (1999) 297–299.
The work was supported by NAS of Ukraine through the depart-
mental academic Project “Kalibr” (2007–2009). The XPS spectra
measurements by Dr. M.V. Dobrotvorskaya and experimental assis-
tance by group of Prof. L.A. Litvinov are greatly acknowledged.
[11] T. Ikegami, J.-G. Li, T. Mori, Y. Moriyoshi, J. Am. Ceram. Soc. 85 (2002)
1725–1729.
References
[12] J.-G. Li, T. Ikegami, J.-H. Lee, T. Mori, J. Am. Ceram. Soc. 83 (2000) 961–
963.
[13] Y. Zhang, H. Yu, Ceram. Int. 35 (2009) 2077–2081.
[14] J.-G. Li, T. Ikegami, T. Mori, J. Am. Ceram. Soc. 88 (2005) 817–821.
[15] K. Nakanishi, P.H. Solomon, Infrared Absorption Spectroscopy, Holden Day, San
Francisco, 1977.
[16] T. Ikegami, Y. Mori, M. Matsuda, H. Suzuki, Yogyo Kyokaishi 81 (1973) 379–
382.
[17] N.L. Smirnova, N.V. Akimova, N.V. Belov, J. Struct. Chem. 8 (1967) 65–68.
[1] J.-G. Li, T. Ikegami, T. Mori, Y. Yajima, J. Am. Ceram. Soc. 87 (2004) 1008–1013.
[2] Yu.L. Kopylov, V.B. Kravchenko, S.N. Bagayev, V.V. Shemet, A.A. Komarov, O.V.
Karban, A.A. Kaminskii, Opt. Mater. 31 (2009) 707–710.
[3] Pat. 10101333 (A) Japan, IC1–7 C04B 35/44; C01F 17/00; H01S 3/16, T. Yanagi-
tani, H. Yagi, M. Ichikawa, Publ. 21.04.98.
[4] Pat. 10101411 (A) Japan, IC1–7 C04B 35/44; C01F 17/00, T. Yanagitani, H. Yagi,
Y. Hiro, Publ. 21.04.98.
[5] N. Matsushita, N. Tsuchiya, K. Nakatsuka, T. Yanagitani, J. Am. Ceram. Soc. 82
(1999) 1977–1984.