Yttrium carbonate thermolysis

Article abstract of DOI:10.1134/S0036023612020076

The thermal stability of carbonate precursors of yttrium oxide was studied by thermal and thermogravimetric analyses, specifically, with evolved gas mass spectroscopy, on TA Instruments equipment. The thermolysis of Y ₂(CO₃)₃ · nH₂O (n = 2.46) is a complex process and comprises several stages of elimination of water (90-285°C) and carbon dioxide. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S0036023612020076

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2012, Vol. 57, No. 2, pp. 237–241. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © P.P. Fedorov, N.V. Il’in, 2012, published in Zhurnal Neorganicheskoi Khimii, 2012, Vol. 57, No. 2, pp. 282–286.
PHYSICAL METHODS
OF INVESTIGATION
Yttrium Carbonate Thermolysis
P. P. Fedorova and N. V. Il’inb
a Prokhorov Institute of General Physics, Russian Academy of Sciences, Leninskii pr. 51, Moscow, 119991 Russia
eꢀmail: ppf@lst.gpi.ru
b INTERTECHꢀCORP, Moscow Representative Office, Moscow, Russia
eꢀmail: www.intertechꢀcorp.ru
Received December 30, 2009
Abstract—The thermal stability of carbonate precursors of yttrium oxide was studied by thermal and thermoꢀ
gravimetric analyses, specifically, with evolved gas mass spectroscopy, on TA Instruments equipment. The
thermolysis of Y2(CO3)3
⋅ nH2O (n = 2.46) is a complex process and comprises several stages of elimination
of water (90–285 ) and carbon dioxide.
°
C
DOI: 10.1134/S0036023612020076
Dispersed yttrium oxide powders are of interest for of the process rate, was carried out on a TGA Q500
use as precursors for manufacturing laser ceramics thermal analyzer. Platinum or Al2O3 crucibles were
which are competitive with single crystals in their used, respectively. Heating rates were 10–20 K/min.
spectral generation properties. These powders are of Experiments were carried out either under air or in an
interest as luminescent materials, too [1, 2]. A carbonꢀ argon or helium flow.
ate process is used to prepare precursors for yttrium
oxide [3–6].
RESULTS AND DISCUSSION
Fedorov et al. [1] showed that, when yttrium is preꢀ
According to Xꢀray powder diffraction and electron
microscopy [1], the sample prepared in run 156 (hereꢀ
after, sample 156) is a powder of yttrium carbonate
cipitated from nitrate solutions by a solution of ammoꢀ
nium hydrocarbonate NH4HCO3, hydrated yttrium
carbonate Y2(CO3)3 nH2O is precipitated to decomꢀ
⋅
Y2(CO3)3
cles with sizes of about 10
⋅
n
H2O, which consists of spherulitic partiꢀ
pose upon heating in several stages. The final product
is yttrium oxide. From dilute solutions, a new comꢀ
pound precipitates in crystals.
Here, our goal was to study the thermolysis of the
phases synthesized in [1] in a detailed way. The study
was carried out on thermoanalytical equipment proꢀ
vided by TA Instruments.
µ
m, these particles in turn
being composed of needlelike crystals; sample 161 is a
new phase formed of nanometerꢀthick platy microcꢀ
rystals of rhombic habit.
The results of thermolyzing sample 156 are shown
in Figs. 1–3. One can see from these figures that the
decomposition of yttrium carbonate is a complex proꢀ
cess and involves several stages. Change in the gaseous
atmosphere has no substantial effect on the occurꢀ
rence of the process. The weight loss value correlates
with heat absorption. At least five extremes are recogꢀ
nized on the DSC curve corresponding to the maximal
rates of the involved reactions, at 95, 285, 550, 610,
EXPERIMENTAL
From ammonium hydrocarbonate NH4HCO3
(pure grade) and distilled water, a solution with a conꢀ
centration of 1.67 mol/L (pH 7.52) was prepared.
Yttrium oxide was dissolved in dilute nitric acid to preꢀ
pare an yttrium nitrate solution. The concentration of
the stock solution (as Y2O3) was 0.0432 mol/L (in run
156) or 0.022 mol/L (in run 161). To the asꢀprepared
solution, the ammonium hydrocarbonate solution was
and 680
°
С
. Of them, well defined is the peak at 610 С.
°
The others are diffuse. Weight loss values referring to
process stages are shown in Fig. 2.
Weight loss ends at 750 С with the formation of
°
dropped (direct titration) under stirring with a magꢀ cubic yttrium oxide (as found by Xꢀray powder diffracꢀ
netic stirrer. Titration was carried out in a pH range of tion [1]). The residual weight is 56.15% of the initial
1.8–5.9. The thusꢀobtained precipitates were filtered weight, corresponding to the formula Y2(CO3)3
⋅
through Blue Band double paper filter and washed 2.46H2O for the initial sample. According to singleꢀ
with distilled water.
crystal Xꢀray diffraction [7], some water in hydrated
yttrium carbonate Y2(CO3)3 H2O (tengerite) is zeoꢀ
lite water; as a result, can vary from 2 to 3.
According to mass spectrometry (Fig. 3), the
⋅
n
Thermogravimetric analysis and differential scanꢀ
ning calorimetry were carried out on an SDT Q600
thermal analyzer. HiꢀRes Dynamic thermogravimetꢀ
n
ric analysis, where the heating rate varied as a function decomposition peak at 610 С is accompanied by pulse
°
237

238
FEDOROV, IL’IN
Weight, %
(а)
1.5
1.0
0.5
0
100
80
0.3
0.2
0.1
60
–0.5
40
0
–1.0
0.4
200
400
Temperature
600
800
, °C
Weight, %
100
(b)
90
80
70
60
0.8
0.2
0.1
0
791.14
53.95%
°С
40
0
200
400
600
800
Temperature, °C
Fig. 1. Differential scanning calorimetry and thermogravimetry results for yttrium carbonate hydrate sample 156: (a) SDT Q600,
sample size: 15.03 mg, argon atmosphere, and heating rate: 10 K/min; and (b) TGA Q500, sample size: 10.30 mg, air atmosphere,
and heating rate: 20 K/min.
evolution of carbon dioxide. In addition, there are difꢀ ination [1]; the crystallization of cubic yttrium oxide is
observed for the final weight loss.
The approximate sequence of reactions may be
described as follows:
fuse СО2 gas evolution peaks at 250, 550, and 680°С.
The appearance of diffuse peaks on thermal curves
signifies the concurrence and incompletion of some
intermediate thermolysis stages. This agrees with the
amorphization of yttrium carbonate upon water elimꢀ
Y2(CO3)3
⋅
2.46H2O
→
Y2(CO3)3
⋅
2H2O + 0.46H2O, (1)
(2)
Y2(CO3)3
⋅
2H2O
→
Y2(CO3)3 + 2H2O,
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 2 2012

YTTRIUM CARBONATE THERMOLYSIS
239
Weight, %
100
80
2.892%
9.388%
18.25%
7.913%
3.487%
60
987.46°С
56.16%
40
0
200
400
600
Temperature, °C
800
1000
Fig. 2. Thermogravimetry results for yttrium carbonate hydrate sample 156: TGA Q500, HiꢀRes Dynamic mode, argon flow, and
sample size: 14.46 mg.
Weight, %
Ion current, mА
0.0006
–2.2
–2.4
–2.6
–2.8
100
80
0.0004
0.0002
60
44.09
0
800
40
0
200
400
Temperature, °C
600
Fig. 3. Differential scanning calorimetry, thermogravimetry, and evolved gas mass–spectrometry results for yttrium carbonate
hydrate sample 156: SDT Q600, sample size: 7.35 mg, helium atmosphere, and gas flow rate: 100 mL/min, and heating rate:
10 K/min.
Y2(CO3)3
2YО1.1(CO3)0.40
The overall thermolysis reaction is as follows:
→
2YО1.1(CO3)0.40 + 2.2СО2,
(3)
(4)
Y2(CO3)3
⋅
2.46H2O
→
Y2O3 + 3СО2 + 2.46H2O. (5)
; the calꢀ
The first stage is substantially over at 95
culated weight loss for reaction (1) is 2.0%. The secꢀ
ond stage (complete dehydration) is substantially over
°
С
→
Y2O3 + 0.8СО2.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 2 2012

240
FEDOROV, IL’IN
Weight, %
Ion current, mА
0.0025
0.0020
0.0015
100
80
–1
–2
–3
18.19
0.0010
0.0005
0
60
44.09
40
0
260
400
Temperature, °C
600
800
Fig. 4. Differential scanning calorimetry, thermogravimetry, and evolved gas massꢀspectrometry results for yttrium oxide precurꢀ
sor sample 161: SDT Q600, sample size: 6.00 mg, helium atmosphere, gas flow rate: 100 mL/min, and heating rate: 10 K/min.
at 285
°
С
. Weight loss on the basis of the initial subꢀ
There are wellꢀdefined three thermolysis stages:
water elimination with the maximal profess rate at
stance (the sum of reactions (1) and (2)) is 10.0%,
which well agrees with the experiment (Fig. 2).
СО2 evolution in reaction (5) corresponds to 33.2%
weight loss. The dynamics of this process was traced by
mass spectrometry (Fig. 3). The process comprises a
diffuse stage accompanied by gradual weight loss; a
sharp stage of basic decomposition at 600–620
residual gas evolution at 620–750 . A semiquantitaꢀ
tive explanation is possible on the assumption of a
gradual formation of yttrium oxocarbonate of compoꢀ
sition YО1.1(CO3)0.40 and the decomposition of the latꢀ
130
product [1]; an intermediate process stage with the
maximal process rate at 360 , involving СО2 evoluꢀ
tion; and the final process stage at 600–650 . At the
°
С to bring about amorphization of the crystalline
°
С
°
С
last stage, crystallization occurs to yield cubic yttrium
oxide. Weight loss values referring to the stages are
shown in Fig. 4. Complete weight loss was 47.08%.
°С; and
°С
Unlike earlier data gained from a bulk sample [1],
this experiment reveals the intermediate decomposiꢀ
tion stage. Further, an exotherm associated with crysꢀ
tallization of an amorphous sample is observed. Such
a process yields nanopowders when interrupted in the
very beginning, as we noticed for yttrium and scanꢀ
dium borates [9, 10].
ter at 600–620 С. Evidence for the formation of this
compound was obtained [8] in the study of yttrium
hydroxocarbonate thermolysis.
°
The product prepared at 620–750 С is an yttrium
°
oxide nanopowder with a noticeable amount (up to
3.5%) of adsorbed carbon dioxide. Presumably, this
product has a high reactivity in diverse processes, in
particular, in sintering.
Comparing Figs. 1–3 to each other and to earlier
data [1], we find that the major thermolysis of
hydrated yttrium carbonate remains the same in variꢀ
ous atmospheres and for various sample sizes.
Remember that Eqs. (1)–(4) are no more than a
scheme of a complex process. When bulk (290–700 mg)
samples were thermolyzed in the Qꢀmode [1], the
The available data are insufficient for finding the
formulation of sample 161. The thermal curve resemꢀ
bles thermolysis of amorphous yttrium hydroxocarꢀ
bonate Y2(OH)2(CO3)2 2H2O as described in [11],
⋅
but is different.
ACKNOWLEDGMENTS
decomposition stage at 560 С was clearly recognized.
°
The authors are grateful to INTERTECHꢀCORP
(USA) for providing them with instruments and to
V.K. Ivanov, A.E. Baranchikov, and S.V. Kuznetsov for
fruitful discussion.
Figure 4 displays thermoanalytical data for the carꢀ
bonate precursor of yttrium oxide synthesized in run
161 [1].
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 2 2012

YTTRIUM CARBONATE THERMOLYSIS
241
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