Phase relations in the Nb-Ni-Sb system

Article abstract of DOI:10.1007/s10789-005-0281-z

Phase relations in the Nb-Ni-Sb system at 1070 K are studied by x-ray diffraction. The results confirm the existence of the ternary compound Nb ₂₈Ni_33.5Sb_12.5 (new structure type), which is shown to have a narrow homogeneity range. The system contains no solid solutions based on binary compounds, as evidenced by structural analysis data for NiSb and NbSb₂ in three-phase Nb-Ni-Sb samples.

Full text of DOI:10.1007/s10789-005-0281-z

Inorganic Materials, Vol. 41, No. 11, 2005, pp. 1166–1171. Translated from Neorganicheskie Materialy, Vol. 41, No. 11, 2005, pp. 1324–1329.
Original Russian Text Copyright © 2005 by Lomnytska, Berezovets.
Phase Relations in the Nb–Ni–Sb System
Ya. F. Lomnytska and V. V. Berezovets
Franko National University, ul. Kirila i Mefodiya 6, Lviv, 79005 Ukraine
e-mail: yalomnytska@yahoo.com
Received July 15, 2005
Abstract—Phase relations in the Nb–Ni–Sb system at 1070 K are studied by x-ray diffraction. The results con-
firm the existence of the ternary compound Nb28Ni33.5Sb12.5 (new structure type), which is shown to have a nar-
row homogeneity range. The system contains no solid solutions based on binary compounds, as evidenced by
structural analysis data for NiSb and NbSb2 in three-phase Nb–Ni–Sb samples.
INTRODUCTION
their lattice parameters, we used the CSD software
package [2].
The Nb–Ni–Sb system was reported earlier to con-
tain a compound of composition Nb28Ni33.5Sb12.5 (new
structure type) [1]. Phase equilibria in this system have
not been investigated. The purpose of this work was to
study the 1070-K phase relations in the Nb–Ni–Sb sys-
tem, construct its phase diagram, identify new ternary
compounds, and find out whether the system contains
solid solutions based on binary compounds.
EXPERIMENTAL RESULTS
Phase relations in the Nb–Ni–Sb system. We rein-
vestigated the constituent binary systems. In the Nb–Ni
binary [3], we obtained the compounds NbNi3 (TiAl3
structure type) and Nb6Ni7 (W6Fe7) [4], both with nar-
row homogeneity ranges. In the Ni–Sb system at
1070 K, we obtained Ni1.12–0.94Sb0.88–1.06 (NiAs) and
Ni5Sb2 (Ni5Sb2) [3, 4]. In the composition range
Ni0.70Sb0.30–Ni0.80Sb0.20, the samples, both unannealed
and annealed at 870 K, contained, in addition to Ni5Sb2,
the high-temperature phase of Ni3Sb (BiF3) and trace
levels of the low-temperature phase of Ni3Sb (Cu3Ti)
[4]. NiSb2 (FeSb2) was found in Sb-rich (>67 mol %
EXPERIMENTAL
Phase relations in the Nb–Ni–Sb system were stud-
ied over the entire composition range using 55 samples
prepared from high-purity (99.9+%) metal powders by
arc melting. At low Sb concentrations, the samples
were sintered in evacuated silica ampules during heat- Sb) Nb–Ni–Sb samples at 870 K. In the Nb–Sb system
ing to 1070 K. At Sb contents above 67 mol %, the tem- at 1070 K, we obtained Nb3Sb (Cr3Si), NbSb2 (OsGe2),
perature was raised to 870 K. After 100 h of sintering,
the samples were ground, pressed, and sintered again.
Next, the samples were homogenized by annealing at
1070 (≤67 mol % Sb) or 870 K (>67 mol % Sb) for
600–800 h, followed by quenching in cold water with-
out breaking the vacuum. In our studies, we used only
those samples which differed in weight from the start-
ing mixture by no more than 2%.
and Nb5Sb4 (Ti5Te4) [4]. NbSb (NiAs) [4], which was
reported to form peritectically [3], was not obtained in
our preparations at 1070 K. At the same time, the XRD
patterns of Nb–Ni–Sb samples quenched from 870 K
and containing more than 50 mol % Sb indicated the
presence of trace levels of that phase. It seems likely
that NbSb forms below 870 K. Nb3Sb2 and Nb4Sb3,
phases with unidentified structures [4], were not
obtained at 1070 or 870 K. We suppose that Nb3Sb2 and
Nb5Sb4 (Ti5Te4) are the same phase. The crystal data for
all of the phases in the Nb–Ni–Sb system are presented
in Table 1.
The phase composition of the samples was deter-
mined by powder x-ray diffraction (XRD) using a
Debye–Scherrer camera (CrK radiation) and DRON-
3M diffractometer (CuKα radiation). Intensity data
were collected in the 2θ range 10°–85° (DRON-3M,
CuKα radiation, step size of 0.05°, counting time of
10 s per data point). Single-crystal XRD measure-
ments were performed on a Nonius Kappa x-ray dif-
fractometer (95-mm CCD chamber, horizontal graph-
ite monochromator, 5.82° ≤ 2θ ≤ 84.22°, MoKα radia-
The 1070-K section of the Nb–Ni–Sb phase dia-
gram inferred from the present XRD results is shown in
Fig. 1. The only ternary compound in the system is
Nb28Ni33.5Sb12.5 (new structure type) [1]. To determine
the composition region of this phase, we prepared sam-
ples with constant Nb and Sb contents, differing in
tion). In solving the structure of crystals and refining composition from the ternary compound by 2 mol %.
0020-1685/05/4111-1166 © 2005 Pleiades Publishing, Inc.

PHASE RELATIONS IN THE Nb–Ni–Sb SYSTEM
Table 1. Crystal data for phases of the Nb–Ni–Sb system
Phase Structure type Sp. gr.
1167
a, Å
b, Å
c, Å
Source
4.3007
Sb
α-As
α-Fe
11.222
[5]
R3 m
Im3m
4.309(2)
3.3014
11.286(8)
This work
[5]
Nb
3.311(3)
3.307(3)
This work
This work
Nb0,96Ni0.02Sb0.02
NbNi
α-Fe
Im3m
R3 m
W6Fe7
5.072(4)
27.65(1)
[4]
Nb1.12–1.06Ni0.88–0.94
NbNi3
5.064(2)–5.109(6)
3.62
28.25(1)–27.33(2) This work
TiAl3
I4/mmm
7.41
[4]
This work
[5]
3.556(1)
3.5239
7.422(2)
Ni
Cu
Cu
Fm3m
Fm3m
Ni0.94Nb0.06
3.563
[4]
3.573(1)
3.5961(6)
3.5582(5)
3.588
This work
This work
This work
[4]
Ni0.93Nb0.05Sb0.02
Ni0.93Nb0.02Sb0.05
Ni0.9Sb0.1
Cu
Cu
Cu
Fm3m
Fm3m
Fm3m
3.574(1)
12.9456
This work
[4]
Ni5Sb2
New
C2
5.4271
(β = 151.71°)
11.457
Ni5.0–5.1Sb2.0–1.9
12.872(2)–12.76(5) 5.4266(6)–5.424(2) 11.425(7)–11.34(5) This work
(β = 151.59(1)°–
151.51(1)°)
NiSb
3.934
4.033–3.914
4.032(2)–3.936(1)
5.2643
5.131
[4]
[4]
Ni1.12–0.94Sb0.88–1.06
NiAs
P63/mmc
5.202–5.135
5.200(1)–5.126(1) This work
Nb3Sb
[4]
Nb3.0–3.1Sb1.0–0.9
Nb5Sb4
Cr3Si
Pm3n
I4/m
5.261(1)–5.311(3)
10.314
This work
Ti5Te4
3.5566
3.5549(6)
8.315
[4]
This work
[4]
10.321(1)
NbSb2
OsGe2
New
C2/m
10.218
3.630
(β = 120.03°)
10.2395(2)
13.2334
3.6318(1)
(β = 120.035(1)°)
8.3322(2)
5.0337
This work
[1]
Nb28Ni33.5Sb12.5
Pnnm
16.5065
13.278(4)–13.206(6) 16.532(5)–16.480(9) 5.049(2)–5.036(2) This work
INORGANIC MATERIALS Vol. 41 No. 11 2005

1168
LOMNYTSKA, BEREZOVETS
Sb
1
2
3
4
NbSb2
(NiSb2)
NbSb
Nb5Sb4
NiSb
Ni5Sb2
Nb3Sb
Nb28Ni33.5Sb12.5
Nb
NbNi
NbNi3
Ni
Fig. 1. 1070-K section of the Nb–Ni–Sb phase diagram in the region 0–67 mol % Sb: (1) single-, (2) two-, and (3) three-phase sam-
ples; (4) samples annealed at 870 K; the dash–dot lines represent 870-K phase equilibria.
30
40
50
60
70
2θ, deg
Fig. 2. XRD pattern of NiSb (Nb Ni Sb sample, CuK radiation).
0.1 0.9
α
INORGANIC MATERIALS Vol. 41 No. 11 2005

PHASE RELATIONS IN THE Nb–Ni–Sb SYSTEM
1169
Solubility of Nb in NiSb and Ni in NbSb2. Nb–Ni–
Sb samples close in composition to NiSb (NiAs) were
XRD single-phase. To assess Nb solubility in NiSb, we
prepared samples containing 5 mol % Nb and different
Ni : Sb ratios within the homogeneity range of
Ni1.12−0.94Sb0.88–1.06 (0.44, 0.46, 0.50, and 0.52 mol %
Sb). The structure of the Nb0.1Ni0.9Sb sample (a =
0.39399(5) nm, c = 0.51413(9) nm) was refined using
powder XRD data with the aim of ascertaining whether
Nb may substitute for Ni or Sb in NiSb.
Table 2. Crystal data for NiSb (Nb0.1Ni0.9Sb sample), inten-
sity data collection conditions, and refinement statistics
Refined composition
NiSb
P63/mmc
Space group
a, Å
3.9399(5)
5.1413(9)
69.12(3)
2
c, Å
V, Å3
The XRD pattern of that sample is shown in Fig. 2.
The crystal data and intensity data collection conditions
are summarized in Table 2. The structure was refined in
space group P63/mmc using the atomic parameters in
the NiAs structure [4] as input data. The Nb occupancy
was free to refine on both the Ni (2a) and Sb (2c) sites.
Final refinement converged to RI = 0.045 at the compo-
sition NiSb (Table 3), indicating that NiSb dissolves
no Nb.
Formula units per cell, Z
Calculated density, g/cm3
Diffractometer
8.676(4)
DRON-3M
Cu; λ = 0.154185
1721.34
Radiation; wavelength, nm
Absorption coefficient, cm–1
[111] texture
2.0700
The sample with the bulk composition ꢀNbNiSb3
was found to contain needlelike single crystals.
According to x-ray spectrochemical analysis results
(JEOL JSM-6400 scanning electron microscope, Labo-
ratoire de Chimie du Solide et Inorganique Molécu-
laire, Université Rennes 1, France), the approximate
composition of one of the crystals was ꢀNbSb2. The
crystal structure of NbSb2 was solved earlier by Rehr
and Kauzlarich [6]. Determining the Nb and Sb site
compositions, we might assess the homogeneity range
of NbSb2 and find out whether it dissolves Ni or not.
Intensity data for that crystal were collected on the
Nonius Kappa diffractometer (Table 4).
Refinement parameters
Refinement procedure
Atomic positions
2θmax; sinθmax/λ, Å–1
RI; Rp
5
Full profile
2
85.27; 0.439
0.0453; 0.1203
Those samples contained, in addition to
Nb28Ni33.5Sb12.5, other phases. XRD examination of the
three-phase samples showed that the lattice parameters
of Nb28Ni33.5Sb12.5 were slightly increased in the
Nb3Sb + NiSb + Nb28Ni33.5Sb12.5 region (a =
1.3278(4) nm, b = 1.6532(5) nm, c = 0.5049(2) nm)
and slightly reduced in the NiSb + NbNi +
Nb28Ni33.5Sb12.5 region (a = 1.3206(6) nm, b =
1.6480(9) nm, c = 0.5036(2) nm) in comparison with
the single-phase material (a = 1.320(8) nm, b =
1.6551(5) nm, c = 0.5019(2) nm). Thus, we are led to
conclude that Nb28Ni33.5Sb12.5 has a narrow homogene-
ity range, no broader than 2 mol %, at a constant Sb
content. For this reason, the composition region of this
ternary compound in Fig. 1 is shown by a dashed line.
Solid solutions based on Nb–Ni or Nb–Sb binary com-
pounds were not detected.
The observed reflections could be indexed in a mon-
oclinic cell, possible space group C2, with lattice
parameters a = 1.02395(2) nm, b = 0.36318(1) nm, c =
0.83322(2) nm, and β = 120.035(14)°. The structure
was solved by the direct method in space group C2/m
using CSD (Table 4). The final difference Fourier map
showed no foreign atoms. To determine site composi-
tions, first a random mixture of Nb and Ni atoms was
placed in the Nb site, and then the Nb and Sb atoms
were permitted to occupy both sites at random. The
lowest agreement factor was obtained with both sites
occupied only by Nb and Sb. The atomic position coor-
dinates and thermal parameters in the structure of
NbSb2 (RF = 0.026 and Rw = 0.038 for 1031 indepen-
Table 3. Atomic position coordinates and thermal parameters in the structure of NiSb (Nb0.1Ni0.9Sb sample)
Atom (site composition)
Position
x
y
z
Biso × 102, nm2
Ni (1.00(4)Ni + 0.00(4)Nb)
Sb (1.00(3)Sb + 0.00(3)Nb)
2a
2c
0
0
0
0.7(3)
0.2(2)
1/3
2/3
1/4
INORGANIC MATERIALS Vol. 41 No. 11 2005

1170
LOMNYTSKA, BEREZOVETS
The bond distances in NbSb2 (Table 6) are close to
Table 4. Crystal data for NbSb2 (sample of composition
~NbNiSb3), intensity data collection conditions, and refine-
ment statistics
the sums of the corresponding atomic radii (rNb
0.147 nm, rSb = 0.141 nm [7]).
=
Thus, our results confirm earlier data on the crystal
structure of NbSb2 [6] and indicate that it has no homo-
geneity range and dissolves no Ni.
Refined composition
NbSb2
Space group
C2/m
10.2395(2)
3.6318(1)
8.3322(2)
120.035(1)°
268.25(2)
3
a, Å
DISCUSSION
b, Å
As a result of systematic studies of the Nb–Ni–Sb
system, we constructed its phase diagram at 1070 K in
the region 0–67 mol % Sb and at 870 K at higher Sb
contents. The only ternary compound in the system is
Nb28Ni33.5Sb12.5. Although the binary compounds in the
Nb–Ni system have some homogeneity ranges, there is
no Nb or Ni solubility in the binary antimonides of this
system, as evidenced by the present structural data for
NiSb and NbSb2 in three-phase samples. The ternary
compound Nb28Ni33.5Sb12.5 has a narrow homogeneity
range.
Just as the Nb–Fe–Sb and Nb–Co–Sb systems [4],
the Nb–Ni–Sb contains only one ternary compound and
no solid solutions based on binary compounds, but the
ternary compounds in the first two systems, NbFeSb
and NbCoSb, have the MgAgAs structure [8]. The Nb–
Ni–Sb system shows less similarity to the Zr(Hf)–
Ni(Co,Fe)–Sb systems, which contain substantially
more ternary compounds, with different crystal struc-
tures [4]. This is attributable to the larger differences in
atomic radius and electronegativity between the transi-
tion metals in the Zr and Hf systems (rNb = 0.1468 nm,
rZr = 0.1602 nm, rNi = 0.1246 nm, χNb = 1.6, χZr = 1.4,
χNi = 1.7) [7, 10]. Consequently, phase relations in ter-
nary systems of two transition metals and antimony are
influenced by the size factor and the difference in
chemical properties between the transition metals.
c, Å
β, deg
V, Å3
Formula units per cell, Z
Calculated density, g/cm3
Absorption coefficient, cm–1
Diffractometer
8.3302(7)
239.15
Nonius Kappa CCD
Mo; λ = 0.071073
4879
Radiation; wavelength, nm
Measured reflections
Independent reflections
Observed reflections
Refinement procedure
Atomic positions
Refinement parameters
2θmax; sinθmax/λ, Å–1
RF; Rw
2923 (I > 1σ(I))
1031 (I > 4σ(I))
F2(hkl)
3
268
84.22; 0.942
0.0261; 0.0377
Substantially more complex phase relations occur in
analogous phosphorus systems. In particular, the Nb–
Ni–P system contains eight ternary compounds [11],
none of which are isostructural with any phase in the
Nb–Ni–Sb or Zr(Hf)–Fe(Co,Ni)–Sb systems. The rea-
son for this is that phosphorus is a typical nonmetal,
dent hkl reflections considered observed on the crite-
rion Fhkl > 4σ(Fhkl)) are listed in Table 5. Refinement in
space group C2 converged to the same R-factor, but
preference was given to the higher symmetry space
group C2/m.
Table 5. Atomic position coordinates and thermal parameters (B × 102, nm2) in the structure of NbSb2 (sample of composi-
tion ꢀNbNiSb3)
*
Atom
Position
ı
y
z
B11
B22
B33
B13
Biso
Nb
4i
4i
4i
0.84791(4)
0.59493(3)
0.14750(3)
0
0
0
0.30972(5) 0.233(9)
0.38735(4) 0.327(6)
0.03457(4) 0.338(6)
0.24(1)
0.27(1)
0.21(1)
0.128(9)
0.249(7)
0.192(7)
Sb(1)
Sb(2)
0.349(8)
0.329(8)
0.350(7)
0.404(7)
0.373(8)
0.321(8)
* B = B = 0.
12
23
INORGANIC MATERIALS Vol. 41 No. 11 2005

PHASE RELATIONS IN THE Nb–Ni–Sb SYSTEM
1171
2. Akselrud, L.G., Grin,Yu.N., Zavalii, P.Yu., et al., CSD—
Universal Program Package for Single Crystal or Powder
Structure Data Treatment, 12th Eur. Crystallographic
Meet. (Moscow, 1989), Moscow: Nauka, 1989, vol. 3,
p. 155.
Table 6. Bond distances in the structure of NbSb2
Atoms
Nb–2Nb
δ, Å
Atoms
δ, Å
3.6318(1)
2.8382(4)
2.8924(5)
2.9113(5)
2.9211(4)
2.9675(6)
3.1416(6)
Sb1–2Nb
2Nb
2.9113(5)
2.9211(4)
2.9675(6)
3.3074(4)
3.3101(5)
3.6169(4)
3.6318(1)
3.7164(4)
2.7773(6)
2.8382(4)
2.8924(5)
3.0408(4)
3.6169(4)
3.6318(1)
3.7164(4)
2Sb(2)
Sb(2)
2Sb(1)
2Sb(1)
Sb(1)
Nb
3. Okamoto, H., Desk Handbook: Phase Diagrams for
Binary Alloys, Metals Park: Am. Soc. for Metals, 2000.
Nb
4. Pearson’s Handbook Desk Edition: Crystallographic
Data for Intermetallic Phases, Villars, P., Ed., Metals
Park: Am. Soc. for Metals, 1997.
2Sb(1)
Sb(1)
2Sb(2)
2Sb(1)
2Sb(2)
5. Elliott, R.P., Constitution of Binary Alloys, Suppl. no. 1,
New York: McGraw-Hill, 1965. Translated under the
title Struktury dvoinykh splavov, Moscow: Metallurgiya,
1970.
6. Rehr, A. and Kauzlarich, S.M., NbSb2, Acta Crystal-
logr., Sect. C: Cryst. Struct. Commun., 1994, vol. 50,
pp. 1177–1178.
Sb2–Sb2
2Nb
Nb
7. Wiberg, N., Lehrbuch der Anorganischen Chemie, New
2Sb(2)
2Sb(1)
2Sb(2)
2Sb(1)
York: Gruyter, 1995, pp. 1838–1840.
8. Evers, C.B.H., Richter, C.G., Hartjes, K., and
Jeitschko, W., Ternary Transition Metal Antimonides
and Bismuthides with MgAgAs Type and Filled NiAs-
Type Structure, J. Alloys Compd., 1997, vol. 252,
pp. 93–97.
9. Tkizawa, H., Uheda, K., and Endo, T., A New High-
Pressure Polymorph of NiSb2, Intermetallics, 2000,
vol. 8, pp. 1399–1403.
while antimony has metallic properties (χSb = 1.8, χP =
2.1 [10]). Moreover, the atomic radius of phosphorus is
notably smaller (rSb = 0.141 nm, rP = 0.110 nm) [7].
10. Pearson, W.B., The Crystal Chemistry and Physics of
Metals and Alloys, NewYork: Wiley, 1972, vol. 1. Trans-
lated under the title Kristallokhimiya i fizika metallov i
splavov, Moscow: Mir, 1977, vol. 1.
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INORGANIC MATERIALS Vol. 41 No. 11 2005