Interaction between samarium and cobalt carbonates in aqueous medium

Article abstract of DOI:10.1134/S0036023610010055

The Sm₂(CO₃)₃-CoCO₃-H ₂O system was studied using isothermal crystallization (295 K). The compounds Sm₂(CO₃)₃ ? 8H₂O, Sm₂Co₅(CO_3<

Full text of DOI:10.1134/S0036023610010055

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2010, Vol. 55, No. 1, pp. 23–26. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © A.G. Burlakova, S.P. Shilkin, 2010, published in Zhurnal Neorganicheskoi Khimii, 2010, Vol. 55, No. 1, pp. 26–29.
SYNTHESIS AND PROPERTIES
OF INORGANIC COMPOUNDS
Interaction between Samarium and Cobalt
Carbonates in Aqueous Medium
A. G. Burlakova and S. P. Shilkin
Institute of Problems of Chemical Physics, Russian Academy of Sciences,
ul. Akademika Semenova 1, Chernogolovka, Moscow oblast, 142432 Russia
Received September 19, 2008
Abstract—The Sm2(CO3)3–CoCO3–H2O system was studied using isothermal crystallization (295 K). The
compounds Sm2(CO3)3 · 8H2O, Sm2Co5(CO3)8 · 30H2O, Sm2Co7(CO3)10 · 40H2O, Sm2Co17(CO3)20 · 54H2O,
and Co(CO3)0.7(OH)0.6 · 2H2O, as well as solid solutions based on samarium carbonate and samarium cobalt
double carbonates were found in the system.
DOI: 10.1134/S0036023610010055
Manufacturing permanent magnets containing
rareꢀearth metals with high magnetic characteristics
include alloying metal components in vacuum inducꢀ
tion or electric arc furnaces, dispersion of the melts by
hydrogen or mechanical treatment in modern milling
and crushing equipment, followed by orientation of
the powders obtained in magnetic field, their compacꢀ
tion, and sintering [1–3]. Alternatively, powders are
prepared in laboratory and industrial practice by
reduction reducing diffusion process based on the calꢀ
EXPERIMENTAL
Starting reagents. The starting reagents were comꢀ
mercially available chemically pure Na2CO3, metallic
samarium (99.83% of purity), and metallic cobalt
(99.99%). Solutions of SmCl3 and CoCl2 were preꢀ
pared by dissolving of corresponding metals in a 12%
HCl solution taken in stoichiometric amounts.
Procedure. Due to low water solubilities of samarꢀ
ium and cobalt carbonates, the title system was studied
using crystallization of carbonates in the course of the
cium thermal reduction of mixtures of oxides, hydroxꢀ reaction of samarium and cobalt chlorides with
sodium carbonate under stoichiometric conditions.
Equilibrium at 295 1 K was reached after 3 to 25 h.
ides, chlorides, carbonates, and other compounds of
rareꢀearth metals and cobalt in a hydrogen atmoꢀ
sphere. This method makes it possible to prepare powꢀ
ders suitable for manufacturing permanent magnets
avoiding the stages of melting and mechanical grindꢀ
ing [2].
In the first set of experiments, a Na2CO3 solution
was added to SmCl3 and CoCl2 solutions; in the second
set, SmCl3 and CoCl2 solutions were added to a
Na2CO3 solution. We either varied the amount of
Na2CO3 added and determined the ratio between Sm
and Co in the products of crystallization, or varied this
ratio at a constant Na2CO3 concentration. In both
cases, the concentrations of the solutions of the initial
However, to obtain homogeneous mixture of variꢀ
ous powdered salts (precursors for production of perꢀ
manent magnets), it is necessary to have information
on the regions of their cocrystallization and coexistꢀ compounds were calculated so that to provide a fixed
concentration of the byꢀproduct NaCl (~0.19 mol/L).
Analyses. Chemical analysis of bottom phases for
samarium, cobalt, chlorine, sodium, and CO2 was carꢀ
ence. In this connection, the aim of this work was to
determine the crystallization fields of samarium cobalt
carbonates in aqueous medium.
Table 1. Compositions of eutonic points in the Sm2(CO3)3–CoCO3–H2O system
Relative contents of the components of the system, wt %
Point
Composition of eutonic points
no.
Sm (CO )
CoCO
3
2
3 3
1
2
3
4
5
98.0
2.0
50.0
62.0
69.0
83.0
Sm2(CO3)3 · 8H2O + solid solutions
50.0
38.0
31.0
17.0
Solid solutions + Sm2Co5(CO3)8 · 30H2O
Sm2Co5(CO3)8 · 30H2O + Sm2Co7(CO3)10 · 40H2O
Sm2Co7(CO3)10 · 40H2O + Sm2Co17(CO3)20 · 54H2O
Sm2Co17(CO3)20 · 54H2O+Co(CO3)0.7(OH)0.6
· xH2O
23

24
BURLAKOVA, SHILKIN
Table 2. Interactions in the Sm2(CO3)3–CoCO3–H2O system
Composition of the bottom phase, wt %
Point no. in the
Ratio, wt %
Sm2(CO3)3
Solid phase
Sm2(CO3)3 8H2O
Schreinemakers ray
Sm2(CO3)3
CoCO3
CoCO3
67.12
4.99
8.83
5.01
75.03
6.02
0.0
0.34
0.44
0.35
1.27
0.38
4.08
0.81
100.0
98.4
0.0
1.6
⋅
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
3
1
2
Solid solutions
97.3
90.1
84.1
82.8
73.2
69.9
63.3
56.2
43.6
44.0
44.8
45.2
36.6
37.2
37.8
16.9
17.6
19.1
19.5
25.5
13.3
2.7
9.9
The same
''
38.56
7.14
15.9
17.2
26.8
30.1
36.7
43.8
56.4
56.0
55.2
54.8
63.4
62.8
62.2
83.1
82.4
80.9
80.5
74.5
86.7
''
13.94
12.72
14.77
20.82
47.84
6.72
11.39
3.38
37.71
4.64
31.62
9.24
18.03
3.92
7.52
3.41
25.31
5.28
25.52
12.84
23.64
3.39
5.38
1.22
1.33
2.58
13.84
1.35
1.92
1.20
1.94
2.83
13.62
7.94
14.92
1.36
3.34
6.50
2.14
3.58
3.98
7.68
19.00
1.82
3.88
2.50
22.08
3.78
24.68
9.72
21.67
3.92
8.60
5.74
31.95
8.89
32.05
20.12
39.75
5.70
8.96
5.53
5.70
8.83
67.27
5.76
8.48
5.56
8.55
10.10
55.55
18.45
40.67
2.52
18.48
37.83
17.80
27.88
28.5
''
''
''
''
''
Sm2Co5(CO3)8 · 30H2O
The same
''
''
Sm2Co7(CO3)10 · 40H2O
The same
''
Sm2Co17(CO3)20 · 54H2O
The same
''
''
''
Sm2Co17(CO3)20 · 54H2O
+ Co(CO3)0.7(OH)0.6 · 2H2O
1.10
1.82
0.0
6.5
0.0
93.5
The same
100.0
Co(CO3)0.7(OH)0.6 · 2H2O
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 1 2010

INTERACTION BETWEEN SAMARIUM AND COBALT
25
I, %
100
Sm2Co17(CO3)20 · 54H2O
50
0
100
Sm2Co7(CO3)10 · 40H2O
50
0
100
Sm2Co5(CO3)8 · 30H2O
50
0
100
Sm2(CO3)3 · 8H2O
50
0
9 14 19 24 29 34 39 44 49 54 59 64 69 74 79 84
2θ, deg
Xꢀray line diagrams of the compounds formed in the Sm (CO ) –CaCO –H O system.
2
3 3
3
2
ried out by routine procedures.. Solid phases were also from 2.0 to 50.0 wt %, solid solutions based on
analyzed for carbon and water.
Sm2(CO3)3 · 8H2O and Sm2Co5(CO3)8 · 30H2O crystalꢀ
lize. In the range from 50.0 to 62.0 wt % CoCO3, comꢀ
plex compound Sm2Co5(CO3)8 · 30H2O exists. In the
range of 62.0–69.0 wt % CoCO3, double carbonate
Sm2Co7(CO3)10 · 40H2O exists; and crystallization of
complex Sm2Co17(CO3)20 · xH2O (x = 54 5.4) is
observed in the range of 69.0–83.0 wt %.
The solid phase composition was found by the
Schreinemakers method [4]. For this purpose, two or
three samples of a bottom phase were analyzed, and
the resulting compositions were connected by
Schreinemakers rays in the Schreinemakers diagram.
The intersection of these rays gave the composition of
the solid phase.
In the region with high CoCO3 concentrations
( 83 wt %), the system has not been studied, because
≥
Xꢀray diffraction studies of carbonates in the
Sm2(CO3)3–CoCO3–H2O system were carried out on a
computerꢀinterfaced ADPꢀ1 diffractometer (Cr
radiation). Xꢀray diffraction patterns were recorded
for 35 min in the presence of the mother liquor.
the effect of hydrolysis is so essential that the system is
no longer ternary, and the basic cobalt carbonate
Co(CO3)0.7(OH)0.6 · xH2O (x = 2.2 0.5) appears in the
bottom phase. The composition was determined by
chemical analysis of the product of the reaction of
CoCl2 with Na2CO3 under stoichiometric conditions.
K
α
RESULTS AND DISCUSSION
Therefore, three double carbonates, a samarium
Six crystallization fields were found in the system carbonate, and a basic cobalt carbonate were found to
Sm2(CO3)3–CoCO3–H2O (Tables 1, 2). Compound exist in the Sm2(CO3)3–CoCO3–H2O system. The
Sm2(CO3)3 · 8H2O crystallizes in the range of up to chemical analysis results are compiled in Table 3.
2.0 wt % CoCO3. In the CoCO3 concentration range Once being separated from the mother liquor, the carꢀ
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 1 2010

26
BURLAKOVA, SHILKIN
Table 3. Chemical analysis of the carbonates found in the Sm2(CO3)3–CoCO3–H2O system
Found, wt %
Compound
Calcd., wt %
Sm
Co
C
H2O
Sm
Co
C
H2O
Sm2(CO3)3 · 8H2O
46.9
18.1
14.8
8.6
–
6.0
5.9
6.0
6.0
5.6
22.2
34.3
35.5
31.0
26.4*
48.12
18.60
14.78
8.65
–
–
5.76
5.94
5.89
6.90
5.70
23.07
33.45
35.44
28.00
24.48
Sm2Co (CO3)8 · 30H2O
18.1
19.7
30.4
39.0
18.23
20.28
28.82
40.04
5
Sm2Co7(CO3)10 · 40H2O
Sm2Co17(CO3)20 · 54H2O
Co(CO3)0.7(OH)0.6 · 2H2O
* Found by difference.
–
bonates gradually lose part of their water. Double carbonꢀ
ates Sm2Co5(CO3)8 · 30H2O, Sm2Co7(CO3)10 · 40H2O
and Sm2Co17(CO3)20 · 54H2O can be used to manafacꢀ
ACKNOWLEDGMENTS
,
We thank I.V. Burlakov for supplying us with the
software and help in calculations according to the
Schreinemakers method.
ture permanent magnets.
Analysis of the Xꢀray powder diffraction data of the
crystallization products in the system shows the
absence of possible admixtures: Na2CO3 NaCl,
REFERENCES
1. F. A. Kuijpers, Philips Res. Repts 28 (2), 1 (1973).
2. Permanent Magnets, Ed. by Yu. M. Pyatin (Energiya,
Moscow, 1980) [in Russian].
3. V. N. Fokin, E. E. Fokina, and S. P. Shilkin, Zh. Prikl.
Sm2O(CO3)2 ·
хH2O, Sm(OH)CO3, CoCO3, basic
cobalt carbonate, as well as crystal hydrate of samarꢀ
ium carbonate Sm2(CO3)3 · 2.85H2O and a complex of
samarium carbonate with sodium carbonate. Thus,
the Xꢀray line diagrams presented in the figure correꢀ
spond to the individual compounds.
Khim. 67 (8), 1372 (1994).
4. F. A. Schreinemakers, Inꢀ, Monoꢀ, and Divariant Equiꢀ
libria (Amsterdam, 1925; Inostrannaya Literatura,
Moscow, 1948).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 1 2010