Phase relations in the Nb-Sb-Si and Nb-Sb-P systems

Article abstract of DOI:10.1134/S0020168510070071

Phase relations in the systems Nb-Sb-Si (0-70 mol % Sb) and Nb-Sb-P (0-50 mol % P) have been studied by X-ray diffraction, and the 1070-K isothermal sections of their phase diagrams have been constructed. The existence of the compound NbSbSi (PbFCl structure) has been confirmed. Both systems contain a few substitutional solid-solution series: Nb₃(Sb,Si) and Nb ₃(Sb,P) (Cr₃Si structure, limiting compositions Nb ₃Sb_0.55Si_0.45 and Nb₃Sb _0.8P_0.2), Nb₃(Si,Sb) and Nb₃(P,Sb) (Ti₃P structure, limiting compositions Nb₃Si _0.6Sb_0.4 and Nb₃P_0.5Sb _0.5), Nb(P,Sb) (NbAs structure, limiting composition NbP _0.8Sb_0.2), and Nb(Si,Sb)₂ (CrSi₂ structure, limiting composition NbSi_1.65Sb_0.35). Phase equilibria in related systems are analyzed.

Full text of DOI:10.1134/S0020168510070071

ISSN 0020ꢀ1685, Inorganic Materials, 2010, Vol. 46, No. 7, pp. 722–727. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © Ya.F. Lomnytska, 2010, published in Neorganicheskie Materialy, 2010, Vol. 46, No. 7, pp. 805–810.
Phase Relations in the Nb–Sb–Si and Nb–Sb–P Systems
Ya. F. Lomnytska
Franko National University, ul. Kirila i Mefodiya 6, Lviv, 79005 Ukraine
eꢀmail: yalomnytska@yahoo.com
Received December 22, 2008; in final form, February 20, 2009
Abstract—Phase relations in the systems Nb–Sb–Si (0–70 mol % Sb) and Nb–Sb–P (0–50 mol % P) have
been studied by Xꢀray diffraction, and the 1070ꢀK isothermal sections of their phase diagrams have been conꢀ
structed. The existence of the compound NbSbSi (PbFCl structure) has been confirmed. Both systems conꢀ
tain a few substitutional solidꢀsolution series: Nb3(Sb,Si) and Nb3(Sb,P)
tions Nb3Sb0.55Si0.45 and Nb3Sb0.8P0.2), Nb3(Si,Sb) and Nb3(P,Sb) Tі3P structure, limiting compositions
Nb3Si0.6Sb0.4 and Nb3P0.5Sb0.5), Nb(P,Sb) (NbAs structure, limiting composition NbP0.8Sb0.2), and
Nb(Si,Sb)2 CrSi2 structure, limiting composition NbSi1.65Sb0.35). Phase equilibria in related systems are
analyzed.
(Cr3Si structure, limiting composiꢀ
(
(
DOI: 10.1134/S0020168510070071
INTRODUCTION
RESULTS AND DISCUSSION
The phase relations in the Nb–Sb–Si and Nb–Sb–P
systems were studied at 1070 K in the regions 0–
70 mol % Sb and 0–50 mol % P, respectively.
First, the compounds known in the constituent binary
systems were shown to exist at 1070 K. The Nb–Si sysꢀ
The Nb–Sb–Si system is known to contain a comꢀ
pound of composition NbSbSi with the PbClF structure
(sp. gr. P4/nmm, а = 3.639, с = 8.179 Å) [1]. Transition
metal–antimony–phosphorus systems have been studꢀ
ied little, except for those containing titanium and zircoꢀ
nium [2]. Phaseꢀdiagram data for the Nb–Sb–P system
are not available in the literature. The purpose of this
work was to study the phase relations in the Nb–Sb–Si
and Nb–Sb–P systems.
tem is known to contain the compounds Nb3Si
structure), ꢀNb5Si3 (W5Si3), and NbSi2 (CrSi2) [2]. The
(Ti3P
α
compounds existing in the Nb–Sb system are Nb3Sb
(Cr3Si), Nb5Sb4 (Ti5Te4), and NbSb2 (OsGe2) [2, 4]. The
Sb–Si system contains no solid solutions. The eutectic is
located at 99.7 mol % Sb, with a melting point of 903 K
[5]. In the Nb–P system, we obtained all the phosphides,
except those with a mole fraction of P above 0.50, which
form at elevated pressures: Nb3P (Ti3P), Nb2P (Nb2P),
EXPERIMENTAL
The Nb–Sb–Si and Nb–Sb–P systems were studied Nb7P4 (Nb7P4), Nb5P3 (Nb5P3), Nb8P5 (Nb8P5), and
NbP (NbAs) [2]. The crystal data for all the phases existꢀ
ing in the Nb–Sb–Si and Nb–Sb–P systems are sumꢀ
marized in Tables 1 and 2.
Nb–Sb–Si system.The Nb–Sb–Si samples prepared
as described above contained no NbSbSi. In view of this,
a number of samples of this composition were sintered at
770, 870, and 1070 K and then annealed at the same temꢀ
perature for 600 h. The phase compositions of those samꢀ
ples are listed in Table 3.
It can be seen from Table 3 that, after the syntheses at
770 and 870 K, the only phase detected by XRD in the
NbSbSi samples was Si; the other phases were Xꢀray
amorphous. Only at 1070 K was the compound NbSbSi
obtained, with impurities of other phases.
Since Nb3Si in twoꢀ and threeꢀphase Nb–Sb–Si
samples had slightly increased lattice parameters and
Nb3Sb had reduced lattice parameters, we studied phase
relations along the 75 mol % Nb join in order to ascertain
the formation of substitutional solid solutions. From the
composition dependences of lattice parameters for the
using
Ӎ1ꢀg samples prepared from 99.7+%ꢀpure metal
and red phosphorus powders. After pressing at 4.9 MPa in
a steel die, the green compacts were sintered at 1070 K for
150 h in evacuated silica ampules. Next, the samples were
ground, reꢀpressed, and sintered in ampules at 1070 K for
an additional 200 h. The sintered Nb–Sb–P samples
were studied with no further processing. Most of the Nb–
Sb–Si samples were arcꢀmelted in an argon atmosphere
and then annealed at 1070 K (or another temperature)
for 800 h in evacuated silica tubes, followed by quenching
in cold water without breaking the vacuum. In our studꢀ
ies, we used only those samples which differed in weight
from the starting mixture by no more than 2%. The phase
composition of the samples was determined by Xꢀray difꢀ
fraction (XRD) with DRONꢀ2.0 (Fe
DRONꢀ3M (Cu
0.05°; counting time per data point, 10–20 s). Lattice
parameters were refined by least squares fitting using
CSD software [3].
K radiation) and
α
K
) diffractometers (scan step (2θ) =
Δ
α
722

PHASE RELATIONS IN THE Nb–Sb–Si AND Nb–Sb–P SYSTEMS
Table 1. Crystal data for phases of the Nb–Sb–Si system
723
Phase
Structure type
Sp. gr.
a,
Å
b
,
Å
c,
Å
Source
3.3014
3.3161 (4)
[7]
This work
Nb
Si
W
Im
Fd
3m
5.42996
5.4266 (8)
[7]
This work
C (diamond)
3m
4.3084
4.3051 (5)
11.247
11.281 (3)
[7]
This work
Sb
α
ꢀAs
R3m
Nb3Sb
5.2643
5.270 (2)
5.207(2)
[2]
This work
This work
Cr3Si
Pm3m
Nb3Sb0.55Si0.45
*
Nb5Sb4
10.314
10.436 (3)
3.5566
3.542 (2)
[2]
This work
Ti5Te4
I4/m
10.218
3.630
8.315
[2]
(β = 120.03°)
3.6310(7)
(β = 120.029(8)°)
NbSb2
Nb3Si
OsGe2
C
2/m
This work
0.230 (2)
8.3289 (6)
10.224
10.228 (8)
10.224 (3)
5.189
5.192 (4)
5.298 (3)
[2]
This work
This work
Ti3P
P
42/
n
*
Nb3Si0.6 Sb0.4
Nb5Si3
10.224
10.076 (4)
10.076 (4)
5.189
5.096 (3)
5.096 (3)
[2]
This work
This work
W5Si3
I4/mcm
*
ӍNb5Si2.6 Sb0.4
NbSi
4.819
4.802 (4)
4.790 (5)
6.592
6.592 (3)
6.490 (4)
[2]
2
CrSi
2
P
6 22
2
This work
*
NbSi Sb0.35
1.65
NbSbSi
3.6388
3.572 (2)
8.179
8.310 (4)
[1]
This work
PbFCl
P4/nmm
* Limit of the solid solution.
Nb3(Sb,Si) and Nb3(Si,Sb) solid solutions (Fig. 1), we extent of the Nb3Pꢀbased solid solution exceeds that of
determined their limits. The lattice parameters of the the Nb3Sbꢀbased solid solution.
limiting solid solutions are indicated in Table 1.
The Sb solubility in NbP reaches 10 mol % (Fig. 5).
The other binary compounds dissolve insignificant
amounts of the third component. The lattice parameters
of the phases existing in the Nb–Sb–P system are listed
in Table 2.
The 1070ꢀK phase equilibria in the composition
region studied are illustrated in Fig. 6.
The Nb–Sb–Si and Nb–Sb–P systems differ someꢀ
what in phase relations. The Nb–Sb–Si system contains
the ternary compound NbSbSi (PbFCl structure),
whereas in the Nb–Sb–P system no compounds were
identified. The likely reason for this is that antimony and
silicon differ in properties more significantly than antiꢀ
mony and phosphorus. At the same time, both systems
NbSi2 dissolves up to 10 mol % Sb, as follows from the
composition dependences of lattice parameters for this
solid solution (Fig. 2). Its lattice parameters decrease
with increasing antimony content. Similar results were
obtained earlier for solid solutions between a transition
metal and antimony, e.g., Ni1 – xSbx and V1 – xSbx [6].
The Nb5Si3ꢀbased solid solution (W5Si3 structure)
extends to the composition ӍNb5Si2.6Sb0.4.
Our results were used to identify phase equilibria in
the region 0–70 mol % Sb and to construct the 1070ꢀK
isothermal section of the Nb–Sb–Si phase diagram
(Fig. 3).
Nb–Sb–P system.Phase relations in the Nb–Sb–P
system were studied in the region 0–50 mol % P at
1070 K, using samples prepared by double sintering.
contain Nb3Eꢀbased (E =
рꢀelement) solid solutions
with ꢀelement substitutions. In the case of Sb and Si
p
The 75 mol % Nb join contains terminal substituꢀ substitutions, the solubility is slightly higher in comꢀ
tional solid solutions. The composition dependences of parison with Sb and P, because Sb and Si differ less in
their lattice parameters (Fig. 4) demonstrate that the atomic radius and electronegativity (rSb = 0.141 nm,
INORGANIC MATERIALS Vol. 46
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724
LOMNYTSKA
Table 2. Crystal data for phases of the Nb–Sb–P system
Phase
Nb3S
Structure type
Sp. gr.
a
,
Å
b
,
Å
c
,
Å
Source
5.2643
5.270(2)
5.205(5)
[2]
This work
This work
Cr3Si
Pm
3m
Nb3Sb0.8P0.2
*
10.314
10.436(3)
3.5566
3.542(2)
[2]
This work
Nb5Sb4
Ti5Te4
OsGe2
I4/m
10.218
3.630
8.315
[2]
[2]
(β = 120.03°)
3.631(1)
(β =120.03(2) )
NbSb2
C2/m
10.231(1)
8.329(4)
°
Nb3P
10.128
10.125(8)
10.137(5)
5.089
5.094(6)
5.126(5)
[2]
This work
This work
Ti3P
P
42/n
Nb3P0.5Sb0.5
*
18.079
18.07(1)
3.425
3.419(2)
13.858
13.896(8)
[2]
This work
Nb2P
Nb2P
Pmma
14.9503
3.4398
(β = 104.74°)
3.431(4)
13.8478
[2]
Nb7P4
Nb5P3
Nb7P4
C2/m
14.917(5)
13.838(6)
This work
(β = 104.54(9)°)
25.384
25.441(1)
3.433
3.440(4)
11.483
11.469(9)
[2]
[2]
Nb5P3
Nb8P5
Pnma
Pbam
26.1998
26.087(9)
9.4652
9.425(3)
3.4641
3.424(2)
[2]
[2]
Nb8P5
NbP
3.3324
3.338(1)
3.342(1)
11.3705
11.3728(6)
11.391(6)
[2]
This work
This work
I
41md
NbAs
NbP0.8Sb0.2
*
* Limit of the solid solution.
Table 3. Phase composition of NbSbSiꢀcontaining samples prepared by sintering at different temperatures
Annealing temperature, K Sample composition
Phase composition
а,
Å
с, Å
770
870
NbSbSi
NbSbSi
NbSbSi
Si
Si
5.433(1)
5.440(2)
NbSbSi
NbSi2 (tr)
Si (tr)
3.572(2)
4.802(1)
5.4360(7)
8.310(4)
6.577(2)
1070
Nb40Sb25Si35
NbSbSi
Nb5Si3(W5Si3)
NbSi2
3.576(3)
9.939(3)
4.799(2)
8.313(7)
5.146(4)
6.573(2)
INORGANIC MATERIALS Vol. 46
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2010

PHASE RELATIONS IN THE Nb–Sb–Si AND Nb–Sb–P SYSTEMS
725
1
, nm3
V
, nm3
2
V
V
, nm3
1
2
0.150
0.130
0.550
0.120
c, nm
0.140
0.540
c, nm
0.530
a
, nm
0.650
0.640
0.530
a
, nm
0.520
0.520
0.480
a, nm
0.470
1.030
0
0.2 0.4 0.6
x
1.020
0.2
0.4
0.6
0.8
Nb3Si
Nb3Sb
x
Fig. 2. Composition dependences of lattice parameters for the
NbSi Sb substitutional solid solution: ( ) singleꢀ and
Fig. 1. Composition dependences of lattice parameters for the
Nb Si Sb and Nb Sb Si substitutional solid soluꢀ
tions: (1) singleꢀ and (2) twoꢀphase samples.
1
2 –
х
х
3
1 –
х
х
3
1 – х х
(2) twoꢀphase samples.
Si
NbSi2
1
2
3
Nb5Si3
NbSbSi
Nb3Si
Nb
Nb3Sb
Nb5Sb4
NbSb2
Sb
Fig. 3. Phase equilibrium diagram of the Nb–Sb–Si system at 1070 K: (1) singleꢀ, (2) twoꢀ, and (3) threeꢀphase samples.
INORGANIC MATERIALS Vol. 46 No. 7 2010

726
LOMNYTSKA
1
2
1
2
V
, nm3
V
, nm3
V
0.150
, nm3
0.110
0.530
0.520
c
0.140
a, nm
0.100
с, nm
1.140
, nm
0.510
0.530
0.520
1.130
0.500
a, nm
a, nm
0.340
1.020
1.010
0.330
Nb3P
Nb Sb
3
0
0.2
0.4
0.6
0.2 0.4 0.6 0.8
x
x
Fig. 4. Composition dependences of lattice parameters for the
Nb P Sb and Nb Sb substitutional solid soluꢀ
Fig. 5. Composition dependences of lattice parameters for the
NbP Sb substitutional solid solution: ( ) singleꢀ and
P
1
3
1 –
x
x
3
1 –
x
x
1 –
x
x
tions: (1) singleꢀ and (2) twoꢀphase samples.
(2) twoꢀphase samples.
NbP
Nb8P5
Nb5P3
Nb7P4
Nb2P
1
2
3
Nb3P
Nb
Nb3Sb
Nb5Sb4
NbSb2
Sb
Fig. 6. Phase equilibrium diagram of the Nb–Sb–P system at 1070 K in the region 0–50 mol % P: (
1) singleꢀ, (2) twoꢀ, and (3) threeꢀ
phase samples.
r
Si = 0.117 nm, rP = 0.110 nm, χSb = 2.04, χSi = 1.9, cially, Zr–Sb–P, which contain the ternary compounds
χP = 2.1 [7, 8]).
Ti2SbP, Zr2SbP, Hf2SbP (Cr2AlС or Ti2SC (ordered TiAs
type) structure) [2, 11], and Zr5Sb3P (Ti5Ge4). The
Nb–Sb–P system contains no compound with the
Nb2SbP stoichiometry, in contrast to the titanium, zircoꢀ
nium, and hafnium systems, probably because the binary
phosphides TiP, ZrP, and HfP have a hexagonal TiAsꢀ
type structure, whereas NbP has a tetragonal NbAsꢀtype
structure. The formation of two compounds in the zircoꢀ
nium system is associated with the larger atomic radius
The Nb–Sb–Si system is similar in phase relations to
other M–Sb–Si systems, in particular to the Zr–Sb–Si
system, which contains two compounds, Zr5SiSb3
(Ti5Ga4) and ZrSi0.7Sb1.3 (PbFCl) [1, 2, 9], and to the
V–Sb–Si system [2, 10], in which P substitutes for Si in
most of the binary compounds to form substitutional
solid solutions.
The phase relations in the Nb–Sb–P system are simꢀ and lower electronegativity of zirconium in comparison
pler in comparison with the systems Ti–Sb–P and, espeꢀ with the other transition metals (rZr = 0.1602 nm, rNb
=
INORGANIC MATERIALS Vol. 46
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PHASE RELATIONS IN THE Nb–Sb–Si AND Nb–Sb–P SYSTEMS
727
2. Villars, P., Pearson’s Handbook Desk Edition: Crystalloꢀ
graphic Data for Intermetallic Phases, Metals Park: Ameriꢀ
can Society for Metals, 1997.
0.1468 nm, χZr = 1.4, χNb = 1.6 [7, 8]). Thus, the phase
relations in the M–Sb–P systems are considerably influꢀ
enced by the nature of the transition metal M.
3. Aksel’rud, L.G., Grin, Yu.N., Pecharsky, V.K., and
Zavalij, P.Yu., CSD 97—Universal Program Package for
Single Crystal and Powder Data Treatment, Version no. 7,
1997.
The phase relations in the Nb–Sb–P and Nb–Sb–Si
systems differ markedly from those in the Nb–Si–P sysꢀ
tem [12, 13], which contains the ternary compound
Nb5Si3P (Mn5Si3ꢀrelated structure), with no analogue in
the Nb–Si–Sb system, even though antimony and phosꢀ
phorus belong to the same periodic group.
4. Lomnytska, Ya.F. and Kuz’ma, Yu.B., The Nb–Sb Sysꢀ
tem, J. Alloys Compd., 2006, vol. 413, pp. 114–117.
5. Okamoto, H., Desk Handbook: Phase Diagrams for Binary
Alloys, Metals Park: American Society for Metals, 2000.
6. Lomnytska, Ya.F. and Pavliv, O.P., Phase Equilibria in the
V–Ni–Sb System, Neorg. Mater., 2007, vol. 43, no. 6,
pp. 692–697 [Inorg. Mater. (Engl. Transl.), vol. 43, no. 6,
pp. 608–613].
CONCLUSIONS
Phase relations in the Nb–Sb–Si system were studied
at 1070 K in the composition region 0–70 mol % Sb, and
the existence of the NbSbSi compound (PbFCl strucꢀ
ture) was confirmed. The system contains the following
substitutional solid solutions: Nb3(Sb,Si)
ture, limiting composition Nb3Sb0.55Si0.45), Nb3(Si,Sb)
Ті3Р Nb3Si0.6Sb0.4), and Nb(Si,Sb)2 CrSi2
NbSi1.65Sb0.35).
7. Emsley, J., Die Elemente, Berlin: Walter de Gruyter, 1994.
8. Holleman–Wiberg Lehrbuch der anorganischen Chemie
,
Berlin: Walter de Gruyter, 1995, pp. 1837–1840.
(Cr3Si strucꢀ
9. Garcia, E. and Corbett, J.D., Chemistry in the Polar
Intermetallic Host Zr5Sb3. Fifteen Interstitial Comꢀ
pounds, Inorg. Chem., 1990, vol. 29, pp. 3274–3282.
(
,
(
,
10. Lomnytska, Ya.F., 1070ꢀK Section of the V–Si–Sb Phase
Diagram, Poroshk. Metall. (Kiev), 2007, vol. 46, nos. 9–
10, pp. 60–65.
11. Boller, H., Gemischte Pnictide mit geordnetem TiPꢀType
(Ti2SCꢀTyp), Monatsh. Chem., 1973, vol. 104, pp. 166–171.
12. Lomnytska, Ya.F. and Koval’, L.V., Phase Relations in the
Phase relations in the Nb–Sb–P system were studied
at 1070 K in the composition region 0–50 mol % Sb. The
following substitutional solid solutions were identified:
Nb3(Sb,Р)
Nb3Sb0.8Р0.2), Nb3(Р,Sb)
Nb(P,Sb) (NbAs, NbP0.8Sb0.2).
(
Cr3Si structure, limiting composition
(Ті3Р Nb3Р0.5Sb0.5), and
,
Nb–Si–P and Ta–Si–P Systems, Zh. Neorg. Khim.
,
1996, vol. 41, no. 11, pp. 1923–1927.
13. Lomnytska, Ya.F., Oryshchyn, S.V., Kuz’ma, Yu.B., and
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INORGANIC MATERIALS Vol. 46
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