A convenient preparation of nano-powders of Y2O3, Y3Al5O12 and Nd:Y3Al5O12 and study of the photoluminescent emission properties of the neodymium doped oxide

Article abstract of DOI:10.1016/j.ica.2017.05.012

[Y(O₂CNBu₂)₃], has been prepared by extraction of the Y³⁺ ions from aqueous solution into heptane by the NHBu₂/CO₂ system. Exhaustive hydrolysis of [Y(O₂CNBu₂)₃] produced the yttrium carbonate [Y₂(CO₃)₃?n H₂O] (n = 2–3), that was converted to Y₂O₃ by thermal treatment at 550 °C for 12 h. The exhaustive hydrolysis of [Y(O₂CNBu₂)₃] and [Al(OBu)₃] (Y/Al molar ratio = 3/5) carried out at room temperature yielded an intermediate mixed carbonate, that, upon heating at 950 °C for 12 h, was converted to Y₃Al₅O₁₂. The exhaustive hydrolysis of [Y(O₂CNBu₂)₃] and [Al(OBu)₃] was repeated in the presence of [Nd(O₂CNBu₂)₃] (Nd/Y molar ratio = 0.07;(Nd + Y)/Al molar ratio = 3:5). The neodymium doped garnet Nd:Y₃Al₅O₁₂ was obtained, through the intermediate formation of a mixed hydroxo-carbonate. For comparison, the neodymium doped garnet was prepared also starting from N,N-dialkylcarbamato complexes of all three metals, [Y(O₂CNBu₂)₃], [Nd(O₂CNBu₂)₃] and [Al₂(O₂CNⁱPr₂)₆] (Nd/Y molar ratio = 0.07;(Nd + Y)/Al molar ratio = 3:5). Also in this case the intermediate mixed hydroxo-carbonate, after heating at 950 °C for 12 h, evolved to Nd:Y₃Al₅O₁₂. FTIR, XRD, SEM, TGA measurements were used for the characterization of the obtained materials. Preliminary studies of the photoluminescent emission properties were carried out on Nd:Y₃Al₅O₁₂. Photoluminescence dynamics have been investigated by means of femtosecond laser pulses and nanosecond temporal resolution up to the millisecond range after excitation. All the luminescence traces have shown a decay time of the order 200 microseconds indicating its potential as a laser medium for infrared emission at 1064 nm.

Full text of DOI:10.1016/j.ica.2017.05.012

Inorganica Chimica Acta xxx (2017) xxx–xxx
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Research paper
A convenient preparation of nano-powders of Y O , Y Al O and Nd:
2
3
3
5 12
Y Al O and study of the photoluminescent emission properties of the
3
5 12
neodymium doped oxide
a
b
c
b
Daniela Belli Dell’Amico , Paolo Biagini , Giovanni Bongiovanni , Stefano Chiaberge ,
a
a,
⇑
a
b
c
Alessio Di Giacomo , Luca Labella , Fabio Marchetti , Gianluigi Marra , Andrea Mura ,
Francesco Quochi , Simona Samaritani , Valerio Sarritzu
c
a
c
a
Dipartimento di Chimica e Chimica Industriale and CIRCC, Università di Pisa, via G. Moruzzi 13, I-56124 Pisa, Italy
Centro Ricerche per le Energie Rinnovabili e l’Ambiente, Istituto Donegani, ENI S.p.A., via G. Fauser 4, I-28100 Novara, Italy
Dipartimento di Fisica, Università degli Studi di Cagliari, I-09042 Monserrato, CA, Italy
b
c
a r t i c l e i n f o
a b s t r a c t
3
+
Article history:
[Y(O CNBu ) ], has been prepared by extraction of the Y ions from aqueous solution into heptane by the
2
2 3
Received 27 February 2017
Received in revised form 2 May 2017
Accepted 7 May 2017
NHBu
2
/CO
2
system. Exhaustive hydrolysis of [Y(O
by thermal treatment at 550 °C for 12 h. The exhaustive
] (Y/Al molar ratio = 3/5) carried out at room temperature
yielded an intermediate mixed carbonate, that, upon heating at 950 °C for 12 h, was converted to
Al 12. The exhaustive hydrolysis of [Y(O CNBu ] and [Al(OBu) ] was repeated in the presence of
[Nd(O CNBu ] (Nd/Y molar ratio = 0.07;(Nd + Y)/Al molar ratio = 3:5). The neodymium doped garnet
Nd:Y Al 12 was obtained, through the intermediate formation of a mixed hydroxo-carbonate. For com-
parison, the neodymium doped garnet was prepared also starting from N,N-dialkylcarbamato complexes
2
CNBu
2
)
3
] produced the yttrium carbonate [Y
2
(CO
3 3
) ꢀn
2
H O] (n = 2–3), that was converted to Y
2 3
O
hydrolysis of [Y(O CNBu ] and [Al(OBu)
2
2
)
3
3
Available online xxxx
Dedicated to Dr. Carlo Mealli on occasion of
his 70th birthday.
Y
3
5
O
2
)
2 3
3
2
2 3
)
3
5
O
Keywords:
i
Metal carbamato complexes
Lanthanides
Yttria
YAG
Nd:YAG
of all three metals, [Y(O
+ Y)/Al molar ratio = 3:5). Also in this case the intermediate mixed hydroxo-carbonate, after heating at
50 °C for 12 h, evolved to Nd:Y Al
FTIR, XRD, SEM, TGA measurements were used for the characterization of the obtained materials.
5 12
Preliminary studies of the photoluminescent emission properties were carried out on Nd:Y Al O .
2 2 3 2 2 3 2 2 2 6
CNBu ) ], [Nd(O CNBu ) ] and [Al (O CN Pr ) ] (Nd/Y molar ratio = 0.07;(Nd
9
3
5 12
O .
3
Luminescence
Photoluminescence dynamics have been investigated by means of femtosecond laser pulses and nanosec-
ond temporal resolution up to the millisecond range after excitation. All the luminescence traces have
shown a decay time of the order 200 microseconds indicating its potential as a laser medium for infrared
emission at 1064 nm.
Ó 2017 Elsevier B.V. All rights reserved.
1
. Introduction
The preparation of finely divided oxides via hydrolysis of molec-
as precursors, metal alkoxides or metal carboxylates are often
encountered [2].
Our experience in the field of the metal carbamato complexes,
[M(O CNR ], drove us to the study of their partial and exhaustive
ular precursors is currently widely exploited [1]. This method of
synthesis allows the use of relatively low temperatures and the
possibility to carry out the process in solvents of low polarity
which are little involved in the particle aggregation process. More-
over, when multi-metal oxides are required, this route could in
principle offer a good level of homogeneity (homogeneity is a
question of length scale [2a]) in the distribution of the different
components of the system. Among the metal complexes chosen
2
2 n
)
hydrolysis [3]. For instance, silicon or aluminum derivatives
undergo complete hydrolysis with formation of dialkylammonium
silicates [NH R ] Si O2n+1 or aluminates [NH R ]Al O(3n+1)/2 [4].
2 2 2 n 2 2 n
Recently, the development of a facile synthesis of lanthanide
carbamato species [5] offered us the availability of a series of
attractive precursors for the preparation of lanthanide oxides or
mixed oxides containing lanthanide centers. Starting from cerium
(
III) N,N-dibutylcarbamate, the hydrated metal carbonates
obtained by hydrolysis at room temperature [6] were readily con-
verted to CeO by treatment at 200 °C in air. The method was
⇑
Corresponding author.
E-mail address: luca.labella@unipi.it (L. Labella).
2
http://dx.doi.org/10.1016/j.ica.2017.05.012
020-1693/Ó 2017 Elsevier B.V. All rights reserved.
0
Please cite this article in press as: D. Belli Dell’Amico et al., Inorg. Chim. Acta (2017), http://dx.doi.org/10.1016/j.ica.2017.05.012

2
D. Belli Dell’Amico et al. / Inorganica Chimica Acta xxx (2017) xxx–xxx
extended to the preparation of nanostructured doped ceria afford-
ing cerium/lanthanum and cerium/terbium mixed oxides contain-
ing a single crystalline phase with the two metals in the preset
molar ratio [7]. The method was adopted with success also for
2. Experimental
2.1. General methods
the synthesis of the stoichiometric lanthanum cuprate La
2
CuO
4
Commercial yttrium oxide (Y O , Strem Chemicals, 99.9%) and
2
3
[
8]. The similar lability [9] of the metal centers involved in the pro-
NHBu2 (Sigma Aldrich, 99+%) were used without further purifica-
tion. Aqueous solutions of yttrium chloride (0.30 M circa) were
prepared by dissolving the appropriate amount of the metal oxide
in diluted hydrochloric acid. The solution was then evaporated to
dryness and the solid residue was dissolved in water. Al(OBu)3
(Sigma Aldrich, 95%) was used directly. In view of the margin of
error about composition declared by the supplier, its aluminum
content was determined by gravimetric methods after hydrolysis
cesses [Ce(III), La(III), Tb(III), Cu(II)] justify the achievement of
these goals. In fact the hydrolysis of the precursors is presumed
to proceed at a similar rate, allowing the simultaneous precipita-
tion of the intimately blended early products, probably crucial
for the prompt obtainment of the desired oxide by the final ther-
mal treatment.
3 5
Yttrium aluminum garnet, Y Al O12 (YAG) is an interesting
i
mixed oxide in view of its features like high hardness, strong
mechanical resistance, really good chemical stability at elevated
temperature, excellent optical properties [10]. In the garnet
yttrium ions can be partially substituted by luminescent lan-
thanide ions without segregation of other phases up to certain lan-
thanide concentration [11], because no considerable geometrical
deformation is involved in view of the similarity of the ionic radii
of lanthanide(III) and yttrium ions. These peculiarities make YAG
a good material to host lanthanide, suitable also for laser prepara-
tion, being able to resist to high intensity radiation. For instance,
neodymium doped YAG is commonly used as laser in the IR region.
Although single crystals have been widely used in this field, cur-
rently a growing interest is addressed to ceramic materials, pre-
pared by powder sintering [12].
and calcination to Al O . [Al (O CN Pr ) ] [21] was prepared
2
3
2
2
2 6
according to literature.
All manipulations except extraction were performed under
dinitrogen atmosphere unless otherwise noted. FTIR spectra in
the solid state were recorded with a Perkin–Elmer ‘‘Spectrum One”
spectrometer, with ATR technique. The metal content of yttrium in
[Y(O CNBu ) ] was determined according to this procedure: a sam-
2
2 3
ple of the product was treated in a platinum crucible with diluted
HNO and the mixture gently warmed; the resulting solution was
3
then evaporated to dryness. After calcination, the weight of the
solid residue [corresponding to the metal oxide Y O ] was deter-
2 3
mined. Volumetric analyses via EDTA titration were also carried
out on the aqueous layer discarded after extraction.
Thermogravimetric analyses were performed on a NETZSCH
STA Jupiter F1 instrument. A weighted amount (about 30 mg) of
solid sample was placed in an alumina crucible and analyzed using
a temperature program from 30 °C to 950 °C with a heating rate of
10 °C/min in dry air atmosphere. The sample weight was recorded
and plotted vs Time/Temperature. According to the weight varia-
tion, the amount of water can be roughly determined and the final
weight of the sample should be related to the residual metal oxide.
The morphology of the samples was characterized using scanning
electron microscopy by a Field Emission Jeol F7600f by using an
5 keV energy electron beam.
The synthesis of pure YAG [10] requires to overcome some
problems, in part related to other stable phases in the Y
system. This system includes, besides the binary oxides Y
Al monoclinic Al (YAM), hexagonal YAlO
orthorhombic YAlO (perovskite, YAP). As a consequence, control
over phase purity is not always achieved [13]. Moreover, when
the preparation of a ceramic material is the goal, easy to sinter
powders are desirable; that means that finely divided solid with
a homogeneous microstructure are required and high tempera-
tures processes resulting in inconvenient growth of the crystallite
sizes must be avoided.
2
O
3
-Al
and
(YAH),
2
O
3
2
O
3
2
O
3
,
Y
4
2
O
9
3
3
Samples were characterized by X-Ray diffraction by means of a
Powder Diffractometer Panalytical X’Pert Pro in Bragg-Brentano
geometry using Cu Ka radiation (k = 1.5416 Å) with the X-ray tube
set to 40 V and 40 mA. The diffractograms were collected in the
range 5–90°(2h) with step size 0.02° and time acquisition set to
15 s/step. Qualitative phase analysis of powder samples has been
carried out by means of standard method [22]. Full profiles fitting
procedures implemented in TOPAS program suite allowed struc-
tural refinements of any recognized phases. Accurate values of
the coherent scattering domain lengths have been obtained by
means of FPA (Fundamental Parameter Approach), an improve-
ment of the Scherrer’s method, implemented in Topas Suite [23].
The PL emission from the neodymium doped powders was
investigated by both time-integrated and time-resolved photolu-
minescence (TPRL) spectroscopy. In the former case, PL emission
was investigated by exciting the samples with a CW Ti: Sapphire
laser operating at 800 nm (Spectra Physics Tsunami). The signals,
dispersed by a spectrometer, were detected with a cooled InGaAs
diode array camera (Andor iDUS 491A). TRPL measurements were
obtained by optically pumping with 790 nm laser pulses of about
150 fs width (FWHM) and 1 kHz repetition rate from a Ti: Sapphire
amplified laser system (Quantronix Integra-I). PL emission was dis-
persed in a spectrometer equipped with a cooled fast phototube
with a 1 ns rising time (Hamamatsu NIR-PMT H10330B-75). The
signal was then analyzed with a 1 GHz oscilloscope (Textronix
TDS 5104).
Among the YAG preparation methods the wet ones are usually
preferred and co-precipitation procedures are often used to obtain
finely divided powder. When metal salts are chosen as precursors,
water is usually the solvent and ammonia or ammonium hydro-
gen-carbonate (directly introduced or produced by urea hydroly-
sis) are the agents inducing precipitation of an early solid
essentially composed by metal hydroxides [14] or metal carbon-
ates [15–17], respectively. Indeed metal carbonates turned out to
be excellent precursors for the preparation of ceramics based on
metal oxide. For instance, yttrium carbonate has been successfully
chosen for the production of highly sinterable yttria powder [18].
As precursors of YAG also alkoxides of both metals [13,19] or a
mixture of aluminum alkoxide and yttrium carboxylate have been
employed [20] by operating in hydro-alcoholic solution.
In this paper we describe the preparation of the yttrium N,N-
dibutylcarbamato complex, its exhaustive hydrolysis and conver-
2 3
sion to nano-structured yttria, Y O , and the preparations of
nano-crystalline YAG, and neodymium doped YAG starting from
solutions containing N,N-dibutylcarbamato complexes of yttrium
and a hydrolysable precursor of aluminum in the Y:Al = 3:5 molar
ratio. Although aluminum is a relatively-inert centre with respect
to the yttrium and lanthanide ones [9], the germinal precipitates
leading to YAG or Nd:YAG by this route show the desired compo-
sition and evolve by thermal treatment to phase pure products
(
powder-XRD) at
a temperature lower than those usually
necessary.
Please cite this article in press as: D. Belli Dell’Amico et al., Inorg. Chim. Acta (2017), http://dx.doi.org/10.1016/j.ica.2017.05.012

D. Belli Dell’Amico et al. / Inorganica Chimica Acta xxx (2017) xxx–xxx
3
2
2
.2. Syntheses
2.2.4. Synthesis of Nd:YAOx1 and Nd:YAOx2
.2.4.1. With Al(OBu) as precursor, Nd:YAOx1. To a solution of [Y
(O CNBu (5.58 g, 9.22 mmol) and [Nd(O
0.067 mmol) in 50 mL of toluene a solution of Al(OBu)
2
3
.2.1. Extraction of yttrium(III) from aqueous solution into heptane by
2
2
)
3
]
2 2
CNBu )
3
]
(44 mg,
3
(4.00 g,
the NHBu
2
/CO
2
system. Synthesis of Y(O
2
CNBu
2
)
3
, 1
n
A solution of dibutylamine (10 mL, 59.3 mmol) was saturated
with carbon dioxide and then 20 mL (6.00 mmol) of an aqueous
solution of YCl3(aq), at 0 °C, were added to the mixture. Upon shak-
ing for a few seconds at 0 °C the organic layer became pale yellow,
while the aqueous phase became colorless. The organic layer was
separated and quickly evaporated at reduced pressure (1,0 ꢁ 10
Torr) at 40 °C. By long drying (5 h) a colorless solid (2.47 g, 71.6%
yield) was obtained. Anal. Calc. for C27 YO : Y, 14.7%; Found
Y, 14.1%. FTIR, ATR: (the most significant bands in the range
15.42 mmol) in 15 mL of DME and 5 mL of BuOH was added. A
solution of water (28.1 mL, 1.56 mol) in 25 mL of THF was added
dropwise to the mixture warmed at 40 °C. A pale grey suspension
was formed. The mixture was refluxed for 4 h, then the suspension
was decanted, the mother liquor was removed and the sticky solid
residue was washed with a THF/toluene solution (25 mL/50 mL) for
two times. The suspension was stirred for 5 h in the course of each
washing procedure. The solvent was every time removed after
decantation and added to the mother liquor: this solution, once
evaporated to dryness, left a negligible amount of residue that
was discarded. The solid was finally dried in vacuo at room temper-
ature for 1 h and at 40 °C for 6 h, Nd:YAlcarb1, (2.77 g). FTIR, ATR
-3
54
H N
3
6
-
1
1
700–1250 cm ): 1528s, 1488s, 1423s, 1376m, 1313s.
–
1
2
.2.2. Exhaustive hydrolysis of 1
(most significant bands, cm ): 3300m (broad), 1506s, 1404s. By
heating the product at 950 °C Nd:YAlox1 was obtained. X-Ray
powder diffraction measurements carried out on a sample of Nd:
YAlox1 showed the presence of a single crystalline phase corre-
To a solution of [Y(O
anhydrous toluene a solution of water (9.60 mL, 0.53 mol) in THF
25 mL) was slowly added dropwise. The mixture was vigorously
2 2 3
CNBu ) ] (6.42 g, 10.6 mmol) in 50 mL of
(
stirred for 3 h at room temperature and the formation of a colorless
suspension was observed. The liquid phase was decanted and the
solid was washed with a THF/toluene solution (25 mL/50 mL) for
two times. The mixture was stirred for 5 h for each washing proce-
dure. The solvent was every time removed after decantation and
added to the mother liquor and the solution, once evaporated to
dryness, left a negligible amount of residue that was discarded.
The solid was dried in vacuo at room temperature for 1 h and at
3 5 12
sponding to the cubic phase of Y Al O .
i
2
[
0
.2.4.2. With [Al
Y(O CNBu
.13 mmol) and [Al
2
(O
2
CN Pr
2
)
6
] as precursor, Nd:YAOx2. A solution of
CNBu (0.086 g,
] (16.6 g, 18.0 mmol) in 350 mL of
2
2
)
3
]
(13.1 g, 21.6 mmol), [Nd(O
2
2 3
) ]
i
2
(O
2
CN Pr
2
)
6
anhydrous toluene was treated under vigorous stirring with a solu-
tion of H O (52.9 mL, 2.94 mol) in THF (50 mL), added dropwise at
2
room temperature and then the suspension was refluxed for 6 h.
The colorless suspension was decanted, the mother liquor was
removed and the solid was washed with a THF/toluene solution
4
H
0 °C for 5 h (Ycarb, 2.09 g; 95.2% yield). Anal. Calc. for [Y
2
(CO
3
)
3
ꢀ3
2
O], Y 12: Y, 43.2%; Found Y, 42.9%. FTIR, ATR: see Results
2 3 6
C H O
and discussion. X-Ray powder diffraction pattern showed the pres-
ence of a single crystalline phase: orthorhombic tengerite(-Y)
(
25 mL/50 mL) for two times. The suspension was stirred for 5 h
in the course of each washing procedure. The solvent was every
time removed after decantation, added to the mother liquor and
evaporated to dryness. The negligible amount of residue was dis-
carded. The colorless solid was dried under vacuum (Nd:YAlcarb2).
FTIR, ATR (most significant bands): 3300w, broad, 1500 s, 1404 s.
This product was treated at 950 °C with conversion to Nd:YAlox2.
X-Ray powder diffraction pattern of Nd:YAlox2 showed the pres-
ence of a single crystalline phase corresponding to the cubic phase
[
Y
2
(CO
3
)
3
ꢀ 2-3 H
2
O, JCPDS card no. 16-0698] [24]. By heating Ycarb
at 550 °C for 8 h, Yox was obtained. X-ray powder diffraction mea-
surements showed the complete conversion to the cubic crys-
talline phase of Y O (space group Ia3, JCPDS card no. 41-1005).
2 3
Further heating did not cause significant mass reduction or appre-
ciable changes in the XRD pattern of the product.
3 5 12
of Y Al O .
2
.2.3. Synthesis of Y
YAlcarb
A solution of [Al(OBu)
and BuOH (5 mL) was added to a solution of [Y(O
5.47 g; 9.03 mmol) in toluene (50 mL) with formation of an opa-
que mixture that was gently warmed up to 40 °C with obtainment
of a clear solution. A solution of H O (1.53 mol) in THF (25 mL) was
3 5
Al O12, (YAlox) with intermediate formation of
3
] (4.0 g; 15.42 mmol) in DME (15 mL)
2 3
CNBu ) ]
3. Results and discussion
2
(
The preparation of the N,N-dibutylcarbamato complex of
yttrium was carried out by extraction of the yttrium ion from the
2
aqueous solution of its chloride into heptane by NHBu
with CO , according to a method previously used with success with
lanthanides [5]. By this approach, the homoleptic derivatives [Ln
(O CNBu ] or the carbonato-carbamato species [NH Bu [Ln (-
CO )(O CNBu or [Ln (CO )(O CNBu are obtained, in
2
saturated
then added dropwise at room temperature. Gas development was
observed. The mixture was vigorously stirred for 3 h with forma-
tion of a colorless suspension. The liquid phase was decanted and
the solid, gelatinous in aspect, was washed with a THF/toluene
solution (25 mL/50 mL) for two times. The mixture was stirred
for 5 h for each washing procedure. The solvent was every time
removed after decantation and added to the mother liquor and
evaporated to dryness leaving a negligible amount of residue that
was discarded. After the washing procedures the colorless solid,
that had acquired a treatable form, was dried in vacuo at room tem-
perature for 1 h and at 40 °C for 8 h. A portion of the product, YAl-
carb, was heated at 950 °C with a mass loss of 49.0%. FTIR-ATR:
2
2
2
)
3
2
2
]
2
4
3
2
2
)
12
]
4
3
2
2 10
) ]
dependence of the reaction conditions and/or the lanthanide iden-
tity. With yttrium, according to the Y content, a product with com-
position [Y(O CNBu ) ], 1, has been obtained with good
2 2 3
reproducibility. The IR spectrum of the compound is similar to
the ones of other lanthanide derivatives with the same formula,
[Ln(O
CN stretching vibrations, in the 1600–1300 cm region.
The exhaustive hydrolysis of [Y(O CNBu ], 1, was carried out
2 2 3
CNBu ) ] (see Table 1) and shows strong bands, due to the
–
1
O
2
2
2 3
)
(
1
most significant bands, cm–1): 3300 m (broad), 1506 m, 1404 m,
328w (sh). The product appeared amorphous after X-Ray diffrac-
tion measurement. TGA (in air, 30-900 °C, TG = 10 °C/min) showed
m = 48.1%. X-Ray diffraction measurements carried out on the
in toluene/THF at room temperature. The yttrium content of the
colorless solid, Ycarb, was in agreement with the formula
Y
2
(CO
presence of a single crystalline phase, corresponding to tengerite
(-Y), with composition Y (CO O, the variable water con-
3
)
3
ꢀ3 H
2
O. Moreover, its XRD pattern (Fig. 1) showed the
D
powder obtained after calcination at 950 °C (YAlox) revealed the
presence of a single crystalline phase corresponding to the cubic
phase of Y Al O .
3 5 12
2
3
)
3
ꢀ2–3 H
2
tent in the mineral being due to its zeolite-type structure [24].
The powder XRD pattern shows an evident anisotropic broadening
Please cite this article in press as: D. Belli Dell’Amico et al., Inorg. Chim. Acta (2017), http://dx.doi.org/10.1016/j.ica.2017.05.012

4
D. Belli Dell’Amico et al. / Inorganica Chimica Acta xxx (2017) xxx–xxx
Table 1
IR spectra of [Y(O
2
CNBu
2
)
3
], 1 and [Ln(O
2
CNBu
2
)
3
] complexes in the region 1700–1300 cm–1: the most significant bands (cm–1).
Y
1528
1488
1423
1376
1313
This work
Ce
Nd
1520
1528
1482
1490
1423
1430
1375
1378
1314
1325
[6]
[5]
Fig. 1. XRD pattern of Ycarb (black) compared with tengerite (red), JCPDS no 01-081-1538. The structural disorder does not allow the refinement.
of the peaks width that cannot be described as quadratic function
of tan(2h). This aspect is more evident along the (0l0) peaks and
probably is due to the elongated fibrous morphology of spherulites
of the sample as well shown by SEM micrograph (Fig. 2).
Also the IR spectrum of our compound (ATR mode) corre-
sponded to the one reported for tengerite(-Y) (KBr disk) [24]. The
most significant bands were observed at 3300 (m, broad) and
tion and decarboxylation of Y
2
(CO
3
)
3
ꢀ3 H
2
O. In view to the zeolite
nature of the product, the variable water content in the samples is
reasonable due to their preliminary treatments before analysis. The
TGA study on Ycarb carried out in air in the temperature range 30–
900 °C (Fig. 3) showed a slow and diffuse weight loss (43.6%), com-
pleted just above 800 °C, in agreement with the formation of Y
starting from Y (CO O, while the transition discerned at
ꢀ2.5 H
around 220 °C (weight loss around 20%) might be ascribed to the
complete loss of water and one molecule of CO . Similar behavior
in TGA analysis of Y (CO O were already observed by
ꢀ2–3 H
Fedorov and coworkers [24a].
2 3
O
2
3
)
3
2
–
1
1
650 (sh) cm attributable to the H
vibrations, respectively, and at 1507 (s), 1466 (m), 1417 (s) cm
attributable to the CO group stretching ones [Table 2].
Products with composition (CO have been
2
O stretching and bending
–
1
2
3
2
3
)
3
2
Y
2
3
)
3
ꢀ2–3
2
H O
reported as obtained by a hydrothermal procedure exploiting the
urea promoted hydrolysis of yttrium nitrate [16] or by treatment
of yttrium nitrate with ammonium hydrogencarbonate in water
The XRD study of the powder obtained after calcination (Yox)
showed the formation of a single crystalline product corresponding
to the cubic phase of Y O (Fig. 4). The average size of the scatter-
2 3
[
25].
Ycarb was completely converted to Y
ing coherent domains were estimated to be 13(2) nm. Heating to
higher temperatures (up to 1100 °C) led only to a narrowing of
the peaks in the XRD pattern due to the gradual increasing of the
mean crystallite size.
2 3
O by heating at 550 °C
for 8 h with a mass loss corresponding to 45.0%, in agreement with
the theoretical value (45.2%) expected for the complete dehydra-
SEM micrographs of Yox (Fig. S1) show a complicated morphol-
ogy of the sample in which there are broken oblate shaped spher-
ulites extended till to 10 mm, which are constituted by elongated
micrometric fibrous aggregates. Each aggregate is composed by a
stack of sub-micrometric thinner fibers of the same length of the
aggregate.
With the aim to prepare YAG in form of a nano-powder, [Y(O
2
-
CNBu ] and [Al(OBu) ] in the appropriate molar ratio were dis-
2
)
3
3
solved at 40 °C in a mixture of solvents (DME/BuOH/toluene/THF)
and hydrolyzed at room temperature. The germinal precipitate,
after the usual work-up, was labelled as YAlcarb. The IR spectrum
–
1
of YAlcarb showed bands at 1506 and 1404 cm attributable to
stretching vibrations of the carbonate moiety (Table 2).
It is not easy to assign a composition to the product. The for-
mula Y
mass loss measured after heating the product at 950 °C with con-
version to the cubic phase of Y Al 12, as discussed below (48.6%
calc. versus 49.0% exp). Anyway, also other formulae of the type Y
Al (CO O, could fit the measured mass loss [28].
(OH)24-2xꢀn H
3
Al
5
(CO
3
)
5
(OH)14ꢀ12 H
2
O is in good agreement with the
3
5
O
3
-
5
3
)
x
2
Fig. 2. SEM image of Ycarb.
Please cite this article in press as: D. Belli Dell’Amico et al., Inorg. Chim. Acta (2017), http://dx.doi.org/10.1016/j.ica.2017.05.012

D. Belli Dell’Amico et al. / Inorganica Chimica Acta xxx (2017) xxx–xxx
5
Table 2
IR spectra of the early hydrolysis products (most significant bands, cm–1) compared with literature data.
Ycarb
Tengerite Y
YAlcarb
3300 (broad)
3500-3000
3300 (broad)
3300 (broad)
3400-3300 (broad)
3450, 3170,, 3020, 2850
1650
1650
1507
1510
1506
1505
1466
1463
1417
1425
1404
1393
This work
[24]
This work
This work
[26]
2
CO
3
)
3
ꢀ2-3 H
2
O
Nd:YAlcarb1
Al (OH)3n-2(CO
NH ][Al(OH) CO
1650
1500-1300 (broad)
n
3
)ꢀhH
2
O
[
4
2
3
]
1540
1450
[27]
Fig. 3. TGA of Ycarb (in air, 30–900 °C, Heating rate = 10 °C/min).
2 3
Fig. 4. XRD pattern of Yox (550) (black) compared with cubic-Y O (black, JCPDS no 41-1105). Body-centred cubic structure (bcc), S.G. Ia3 a = 10.620(2) Å.
The TGA study on YAlcarb, carried out in air in the temperature
range 30-900 °C, is reported in Fig. 5. The weight loss (48.1%) pro-
ceeds slowly and without any discrete transition, till to about
temperatures showed that in the course of their hydration and
decarboxylation they remained amorphous up to 850 °C. After
heating at 950 °C for 4 h YAlcarb transformed into a derivative,
YAlox, showing an XRD pattern corresponding to the one of cubic
YAG (Fig. 6).
5
00 °C agreeing with the formation of Y
3 5
Al O12 starting from the
supposed early formulation.
The XRD pattern of the powder revealed that the material was
amorphous and a study on samples progressively treated at higher
The average size of the scattering coherent domains were esti-
mated to be 42(2) nm. Heating to higher temperatures (up to
Please cite this article in press as: D. Belli Dell’Amico et al., Inorg. Chim. Acta (2017), http://dx.doi.org/10.1016/j.ica.2017.05.012

6
D. Belli Dell’Amico et al. / Inorganica Chimica Acta xxx (2017) xxx–xxx
Fig. 5. TGA of YAlcarb (in air, 30–900 °C, TG = 10 °C/min).
Fig. 6. XRD pattern of YAlox (black) compared with YAG peaks (JCPDS no 00-033-0040). Body-centered cubic structure (bcc), S.G. Ia3d, a = 12.0170(4) Å.
1
100 °C) did not lead to appearance of other crystalline phases, but
the thermal dehydration and decarboxylation. It is reasonable to
presume that the presence of a small percentage of neodymium
does not significantly modify the process of precipitation, therefore
Nd:YAlcarb1 should differ from YAlcarb essentially since it is
formed at higher temperature.
only to a narrowing of the peaks due to crystal growth.
On the base of this favorable outcome, similar procedures were
tried for the synthesis of neodymium doped YAG. A former attempt
3 2 3
was performed starting from 1, [Al(OBu) ] and [Nd(OCNBu ) ] in
the 2.98:5:0.02 molar ratio. The hydrolysis was carried out in the
solvent mixture DME/BuOH/toluene/THF, in this case at the reflux
temperature (about 110 °C) to accelerate the process. The solid
obtained after washing and drying procedures, Nd:YAlcarb1,
transformed to Nd:YAG by heating at 950 °C with a mass loss of
Nd:YAlcarb1 showed in its IR spectrum (table 2) absorptions
attributable to water and carbonato groups. The XRD study of the
powder deriving by its calcination at 950 °C (Nd:YAlox1) (Fig. 7)
revealed the presence of only one crystalline phase with the peaks
essentially congruent with the ones of cubic body centered YAG.
The average size of the scattering coherent domains were esti-
mated to be 42(2) nm.
3
8.8%. A derivative with the composition Y
3
Al
5
(OH)16(CO
3
)
4
ꢀn
2
H O (n about 4) has been reported in the literature as produced
by hydrolysis of aluminum and yttrium salts in the presence of
urea carried out in water at 95 °C [28]. We suggest the composition
The comparison of the powder diffraction pattern of Nd:YAlox1
with the reference pattern of YAG (JCPDS 33-0040) suggests a sub-
stantial equivalence of the structure. A profile fitting on the YAG
peaks leads to a lattice parameter of 12.0416 Å, greater than the
Y
2.98Nd0,02Al
5
(OH)16(CO
3
)
4
ꢀn H
2
O (n about 4) for our compound
since it is in good agreement with the measured mass loss due to
Please cite this article in press as: D. Belli Dell’Amico et al., Inorg. Chim. Acta (2017), http://dx.doi.org/10.1016/j.ica.2017.05.012

D. Belli Dell’Amico et al. / Inorganica Chimica Acta xxx (2017) xxx–xxx
7
Fig. 7. XRD pattern of Nd:YAlox1 (black) compared with YAG peaks (blue, JCPDS no 00-033-0040). Body-centered cubic structure (bcc), S.G. Ia3d a = 12.0416(2) Å. (For
interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
value estimated for YAG, as expected for the partial substitution of
with this transition is in the range of hundreds of ls, depending
on the preparation method of the sample [29]. Furthermore, one
3
+
3+
Y
by the larger Nd ions. This interpretation is consistent with
the observed progressively greater shift of the peaks at lower val-
ues of 2h with respect to the YAG ones.
The composition of the product, in view of the complete precip-
itation of the metal ions, can be considered very close to
of the main features of Nd-doping in the field of solid state lasers
(NIR spectral range) is related to the dense packaging of levels
4
placed at higher energies than the emitting level
F3/2, which can
extend from NIR to UV. Excitation from these levels quickly relaxes
4
4
4
Y
2.98Nd0.02Al
5
O
12
.
to the F3/2 level and thus the I9/2 ? F5/2 absorption band can be
used as efficient optical pumping band in this kind of four-level
laser system [29]. In this work excitation of the PL of Nd:YAlox1
samples was achieved using pulsed or CW radiation at about
800 nm as reported in the experimental section. In order to avoid
overheating of the sample, the excitation power density was
Low magnification SEM micrographs of YAlox and Nd:YAlox1
Figs. S2 and S3, respectively) show in both cases compacted pow-
(
ders with dimensions ranging from tens to hundreds mm without
any particular internal fine morphology.
An alternative preparation of a neodymium doped garnet was
2
carried out with a procedure similar to the one described above
always kept below 100 mW/cm .
i
but with the use of freshly prepared [Al
2
(O
2
CN Pr
2
)
6
] instead of
The PL spectrum of Nd:YAlox1 is shown in Fig. 8 in the 1000–
1500 nm spectral window. A narrow intense peak stands out at
1064 nm, that can be ascribed to the main transition
commercial aluminum tri-butoxide. Also in this case the yttrium,
aluminum and neodymium precursors were used in 2.98:5:0.02
Y:Al:Nd molar ratio in order to produce again, as ultimate product,
4
4
F
3/2 ? I11/2. The signal centered at 1124 nm is also related to
5
a species with the composition of Y2.98Nd0.02Al O12. The hydrolysis,
the same transition, while the ones around 1330 nm are related
to the F3/2 ? I13/2 transition. The structured nature due to crys-
talline field effects of these signals, is also well recognizable [30]
and all these results are in good accordance with the literature
[31].
4
4
carried out in toluene/THF at the reflux temperature, produced an
early product, Nd:YAlcarb2, that underwent a loss mass by heating
at 950 °C analogous to the one observed for Nd: YAlcarb1
described above. The IR spectra of the two products resulted very
similar, too. Moreover, the XRD study of the powder deriving by
its calcination at 950 °C (Nd:YAlox2) revealed the presence of only
one crystalline phase with a pattern superimposable to the one of
Nd:YAlox1.
Although the hydrolysis processes are expected to proceed with
a different path and to involve different intermediates, the use of
the aluminum carbamato complex in substitution of commercial
[
3
Al(OBu) ] did not affect the nature of the products in the described
conditions.
3.1. Optical measurements on Nd:YALox1
The PL emission properties of the Nd:YAlox1 powders were
investigated by CW and transient PL spectroscopy. The aim was
to gain insight into the energies and lifetimes of the excited states
of the doping ion Nd3 in Nd:YAlox1, which is a candidate for
applications such as laser media.
+
According to literature, the 4F3/2 ? 4I11/2
transition
m) is reported to be the most intense among
all the other radiative decays. The radiative lifetime associated
(DE = 1,165 eV, 1064 l
Fig. 8. Emission spectra (range 1500–1000 nm) of Nd:YAlox1 powders
(kexc = 800 nm).
Please cite this article in press as: D. Belli Dell’Amico et al., Inorg. Chim. Acta (2017), http://dx.doi.org/10.1016/j.ica.2017.05.012

8
D. Belli Dell’Amico et al. / Inorganica Chimica Acta xxx (2017) xxx–xxx
Scheme 1. Reactions and species involved in metal carbamato complex hydrolysis.
(
2) Alkyl-ammonium alkylcarbamate formed in the course of
the metal carbamato complex hydrolysis (Scheme 1) can
act as a surfactant preventing a significant aggregation of
the particles. At the same time it is easy to remove it under
vacuum.
(
(
3) The endogenous production of alkyl-ammonium hydrogen-
carbonate (Scheme 1) in the course of hydrolysis favors the
formation of metal carbonates, hydroxo- or oxo-carbonates.
4) When two or more metal precursors are used in a certain
molar ratio, the early precipitates are probably mixtures of
carbonato-, hydroxo- and hydroxocarbonato derivatives,
but in the raw mixture an intimate blend of the different fine
particles is achieved that favors the evolution towards the
desired composition of the mixed oxide upon the appropri-
ate thermal treatment.
Fig. 9. Photoluminescence decay 1064 nm of Nd:YAlox1 powders. The red line
represents the mono-exponential best fit.
The PL spectrum is in good agreement with the data reported in
literature for the Nd:YAG species [30,31d], confirming the presence
3
+
of Nd excited ions in the solid matrix. PL measurements on differ-
ent spots of the same sample and in different samples of the same
species showed similar results to those reported in Fig. 8, ensuring
the homogeneity of the Nd:YAlox1 product.
As the rare earth carbamato complexes here used are easily and
promptly obtained by the metal oxides, their choice is particularly
convenient. About aluminum precursors the carbamato complexes
have to be prepared in strictly anhydrous conditions, therefore the
alternative use of a commercial easily hydrolysable product was
attractive. Nevertheless, the comparison with the preparation car-
ried out with the use of a carbamato complex also for the alu-
minum was considered interesting. The preparation of the
neodymium doped YAG was then conducted in both ways, either
starting with [Al(OBu)
gous results.
Photoluminescence spectra and lifetime measurements con-
firmed the good optical quality of the Nd:YAG powders, hence
demonstrating their potential for the development of new NIR
ceramic laser materials.
Fig. 9 shows the time resolved photoluminescence decay for the
4
4
transition
F3/2 ? I13/2 in the Nd:YAlox1 powders after pulsed
excitation at 800 nm with 1KHz repetition rate. From this figure
it can be easily seen that the residual photoluminescence signal
after 1 ms from the excitation pulse is negligible. The best fit of
the experimental data (the red line in Fig. 9) is in good agreement
i
2
-10
3
] or with [Al
2
(O
2
CN Pr
2
)
6
] obtaining analo-
with a mono exponential decay with a
v
= 5 ꢀ 10 over the 500
points (gray dots) reported in the plot. The luminescence intensity
as a function of the time I(t), can be thus written as
ꢀt
T
ꢁ
IðtÞ ¼ Ið0Þ exp ꢂ
where I(0) is the time intensity immediately after excitation, and
s
4
4
Acknowledgements
is the average lifetime of the transition F3/2 ? I13/2. The decay con-
stant obtained from the fitting is = 217 ± 1 ms.
This result is in good agreement with those (
s
s
This work was supported by the Università di Pisa (Fondi di Ate-
neo 2015 and PRA_2016_50 Materiali Funzionali, Progetti di
Ricerca di Ateneo) and by MIUR PRIN 2015.
s
ꢃ260 ms)
reported in literature for Nd:YAG single crystals [30a]. The small
difference between the values can be ascribed to the different
nature of the samples (powder, as in this work, or single crystals)
[
31a].
The experimental decay constant
powders are also in good agreement with the ones reported for Nd:
YAG (237.6 s,1,0%) ceramics [32], showing that the Nd:YAlox1
Appendix A. Supplementary data
s
measured for the Nd:YAlox1
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.ica.2017.05.012.
l
powders can be a good candidate for the fabrication of new cera-
mic media for lasers operating in the NIR region.
References
[
1] (a) E. Hemmer, C. Cavelius, V. Huch, S. Mathur, Inorg. Chem. 54 (2015) 6267;
4
. Conclusions
(
(
b) Ł. John, P. Sobota, Acc. Chem. Res. 47 (2014) 470;
c) M.J. Veith, Chem. Soc., Dalton Trans. (2002) 2405;
The preparation methods of YAG and neodymium doped YAG
(d) G.A. Seisenbaeva, V.G. Kessler, Nanoscale 6 (2014) 6229;
e) P. Dolcet, S. Diodati, M. Casarin, S. Gross, J. Sol-Gel. Sci. Technol. 73 (2015)
91.
(
5
here described offers some advantages as reported below.
[
2] (a) U. Schubert, J. Sol-Gel Sci. Techn. 79 (2016) 249;
(b) G.A. Seisenbaeva, V.G. Kessler, Nanoscale 4 (2014) 22606;
(c) M. Mehring, Coord. Chem. Rev. 251 (2007) 974;
(
1) The molecular nature of the complexes where the metal cen-
ters are surrounded by ligands with large lipophilic moieties
allows the dissolution of the precursors in a scarcely polar
medium where the interactions between the germinal
hydrolysis products and the solvent are negligible. As a con-
sequence a low solubility of the products is expected that
leads to their complete precipitation in form of finely
divided powder.
(
(
(
d) L.G. Hubert-Pfalzgraf, J. Mater. Chem. 14 (2004) 3113;
e) C.D. Chandler, C. Roger, M.J. Hampden-Smith, Chem. Rev. 93 (1993) 1205;
f) M. Hayward, Comprehen. Inorg. Chem. II (2) (2013) 417;
(g) S. Daniele, L.G. Hubert-Pfalzgraf, Mat. Lett. 58 (2004) 1989.
3] D. Belli Dell’Amico, F. Calderazzo, L. Labella, F. Marchetti, G. Pampaloni, Chem.
Rev. 103 (2003) 3857;
D. Belli Dell’Amico, F. Calderazzo, L. Costa, E. Franchi, L. Gini, L. Labella, F.
Marchetti, J. Molec. Struct. 890 (2008) 295.
[
Please cite this article in press as: D. Belli Dell’Amico et al., Inorg. Chim. Acta (2017), http://dx.doi.org/10.1016/j.ica.2017.05.012

D. Belli Dell’Amico et al. / Inorganica Chimica Acta xxx (2017) xxx–xxx
9
[
4] (a) D. Belli Dell’Amico, F. Calderazzo, M. Dell’Innocenti, Eur. Pat. Appl. EP
94669, Oct. 31 1990. (b) D. Belli Dell’Amico, F. Calderazzo, M. Dell’Innocenti,
P. Robino, US Pat. 5 198 565, Mar. 30 1993.
5] L. Armelao, D. Belli Dell’Amico, P. Biagini, G. Bottaro, S. Chiaberge, P. Falvo, L.
Labella, F. Marchetti, S. Samaritani, Inorg. Chem. 53 (2014) 4861.
6] D. Belli Dell’Amico, M. De Sanctis, R. Ishak, S. Dolci, L. Labella, M. Lezzerini, F.
Marchetti, Polyhedron 99 (2015) 170.
7] D. Belli Dell’Amico, P. Biagini, S. Chiaberge, L. Falchi, L. Labella, M. Lezzerini, F.
Marchetti, S. Samaritani, Polyhedron 102 (2015) 452.
(c) A. Kern, A.A. Coelho, R.W. Cheary, Convolution based profile fitting –
diffraction analysis of the microstructure of materials, in: E.J. Mittemeijer, P.
Scardi (Eds.), Materials Science, Springer, 2004, pp. 17–50. ISBN 3-540-40510-4.
[23] A.X.S. Bruker, TOPAS V4: General profile and structure analysis software for
powder diffraction data. User’s Manual, Bruker AXS, Karlsruhe, Germany,
2008.
[24] R. Miyawaki, J. Kuriyama, I. Nakai, Am. Mineral. 78 (1993) 425.
[25] (a) P.P. Fedorov, E.A. Tkachenko, S.V. Kuznetsov, V.V. Voronov, V.V. Osiko, K.S.
Samarina, N.I. Batyrev, I.V. Gontar’, V.K. Ivanov, Russ. J. Inorg. Chem. 55 (2010)
821;
(b) P.P. Fedorov, N.V. Il’in, Russ. J. Inorg. Chem. 57 (2012) 237.
[26] A. Packter, K.S. Panesar, Cryst. Res. Technol. 22 (1987) 1015.
[27] P. Wang, Z.D. Zhao, L.W. Bi, Y.X. Chen, L. Zhang, L.T. Sun, Mater. Res. Innov. 16
(2012) 121.
[28] D. Sordelet, J.M. Akinc, M.L. Panchula, Y. Han, M.N. Han, J. Eur. Ceram. Soc. 14
(1994) 123.
3
[
[
[
[
[
8] D. Belli Dell’Amico, A. Di Giacomo, L. Falchi, L. Labella, M. Marelli, C.
Evangelisti, M. Lezzerini, F. Marchetti, S. Samaritani, Polyhedron 123 (2017) 33.
9] (a) S. Kobayashi, S. Nagayama, T. Busujima, J. Am. Chem. Soc. 120 (1998) 8287;
(
(
(
b) M. Eigen, Pure Appl. Chem. 6 (1963) 97;
c) A. Cusanelli, U. Frey, D.T. Richens, A.E. Merbach, J. Am. Chem. Soc. 118
1996) 5265.
[
[
[
10] S. Bhattacharyya, S. Ghatak, Trans. Ind. Ceram. Soc. 66 (2007) 77.
11] X. Zhang, W. He, Y. Yue, Y. Zhang, CrystEngComm 15 (2013) 8029.
12] (a) J. Li, Y. Pan, Y. Zeng, W. Liu, B. Jiang, J. Guo, Int. J. Refract. Metals Hard Mat.
[29] A. Yariv, Quantum Electronics, 3rd ed., Wiley, 1989.
[30] (a) A. Lupei, V. Lupei, J. Luminescence 169 (2016) 426;
(b) K. Semwa, S.C. Bhatt, Inter. J. Phys. 1 (2013) 15.
3
9 (2013) 44;
(
b) J. Sanghera, W. Kim, G. Villalobos, B. Shaw, C. Baker, J. Frantz, B. Sadowski, I.
[31] (a) Y. Zhydachevskii, I.I. Syvorotka, L. Vasylechko, D. Sugak, I.D. Borshchyshyn,
A.P. Luchechko, Y.I. Vakhula, S.B. Ubizskii, M.M. Vakiv, A. Suchocki, Opt. Mater.
34 (2012) 1984;
Aggarwal, Opt. Mat. 35 (2013) 693.
[
[
[
13] S.-M. Sim, K.A. Keller, T.-I. Mah, J. Mat. Sci. 35 (2000) 713.
14] P. Apte, H. Burke, H. Pickup, J. Mat. Res. 7 (1992) 706.
15] D. Sordelet, J.M. Akinc, M.L. Panchula, Y. Han, M.N. Han, J. Eur. Ceram. Soc. 14
(b) A. Wajler, H. Weglarz, A. Sidorowicz, L. Zich, M. Nakielska, K. Jach, H.
Tomaszewski, Opt. Mater. 50 (Part A) (2015) 40;
(
1994) 123.
(c) H. Qin, J. Jiang, H. Jiang, Y. Sang, D. Sun, X. Zhang, J. Wang, H. Liu,
CrystEngComm 16 (2014) 10856;
(d) J.E. Geusic, H.M. Marcos, H.M. Van Uitert, Appl. Phys. Lett. 4 (1964) 182.
[32] (a) J. Lu, M. Prabhu, J. Song, Ch. Li, J. Xu, K. Ueda, A. Kaminskii, H. Yagi, T.
Yanagitani, Appl. Phys. B 71 (2000) 469;
[
[
[
[
16] Y. Zhang, M. Gao, K. Han, Z. Fang, X. Yin, Z. Xu, J. Alloys Comp. 474 (2009) 598.
17] J.-G. Li, T. Ikegami, J.-H. Lee, T. Mori, J. Am. Ceram. Soc. 83 (2000) 961.
18] N. Saito, S.-I. Matsuda, T. Ikegami, J. Am. Ceram. Soc. (1998) 2023.
19] W. Si, C. Ding, S. Ding, J. Nanomat. 2014 (2014), http://dx.doi.org/10.1155/
2
014/408910 408910.
(b) Spectroscopic and Stimulated Emission Characteristics of Nd3+ in
Transparent YAG Ceramics(b) G.A. Kumar, J. Lu, A.A. Kaminskii, K.-I. Ueda,
H. Yagi, T. Yanagitani, N.V. Unnikrishnan, IEEE J. Quant. Electron. 40 (2004)
747.
[
[
20] G. Goowda, J. Mat. Sci. Letters 5 (1986) 1029.
21] U. Abram, D. Belli Dell’Amico, F. Calderazzo, S. Kaskel, L. Labella, F. Marchetti,
R. Rovai, J. Strahle, Chem. Commun. (1997) 1941.
[
22] (a) R.W. Cheary, A.A. Coelho, J. Appl. Cryst. 25 (1992) 109;
(
(
b) R.W. Cheary, A.A. Coelho, J.P. Cline, J. Res. Natl. Inst. Stand. Technol. 109
2004) 1;
Please cite this article in press as: D. Belli Dell’Amico et al., Inorg. Chim. Acta (2017), http://dx.doi.org/10.1016/j.ica.2017.05.012