The system Ce-Zn-B at 800 °c

Article abstract of DOI:10.1016/j.jssc.2011.08.020

The isothermal section for the system CeZnB has been established at 800 °C using electron microprobe analysis and X-ray powder diffraction. No ternary compounds exist and mutual solid solubilities of binary phases are negligible. In the concentration range of 10.010.5 at% Ce two structural modifications have been confirmed: high temperature βCe₂Zn ₁₇ above ～750 °C with the Th₂Zn₁₇ type (R3m, a=0.90916(4) nm, c=1.3286(1) nm) and low temperature αCeZn ₇ (Ce_1-xZn_52x; x～0.33) up to 750 °C for which we attributed the TbCu₇ type (P6/mmm, a=0.52424(2), c=0.44274(1) nm). The crystal structure of CeZn₇ was derived from the Rietveld refinement of X-ray powder intensities. Precise data on atom site distribution and positional parameters have been furthermore provided from X-ray single crystal refinements for two compounds, for which crystal structures hitherto have only been derived from X-ray diffraction photographs: Ce ₃Zn₁₁ (Immm, a=0.45242(2) nm, b=0.88942(3) nm, c=1.34754(4) nm) and Ce₃Zn₂₂ (I4₁/amd; a=0.89363(2) nm, c=2.1804(5) nm).

Full text of DOI:10.1016/j.jssc.2011.08.020

Journal of Solid State Chemistry 184 (2011) 2840–2848
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Journal of Solid State Chemistry
journal homepage: www.elsevier.com/locate/jssc
The system Ce–Zn–B at 800 1C
n
Z. Malik a, O. Sologub a, G. Giester b, P. Rogl a,
a Department of Physical Chemistry, University of Vienna, Waehringerstrasse 42, A-1090 Vienna, Austria
b Institute of Mineralogy and Crystallography, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
a r t i c l e i n f o
a b s t r a c t
Article history:
The isothermal section for the system Ce–Zn–B has been established at 800 1C using electron
microprobe analysis and X-ray powder diffraction. No ternary compounds exist and mutual solid
solubilities of binary phases are negligible. In the concentration range of 10.0–10.5 at% Ce two
Received 1 July 2011
Received in revised form
10 August 2011
structural modifications have been confirmed: high temperature
¯
b
Ce2Zn17 above ꢀ750 1C with the
Accepted 14 August 2011
Available online 23 August 2011
Th2Zn17 type (R3m, a¼0.90916(4) nm, c¼1.3286(1) nm) and low temperature
a
CeZn7 (Ce1ꢁxZn5þ2x;
xꢀ0.33) up to 750 1C for which we attributed the TbCu7 type (P6/mmm, a¼0.52424(2), c¼
0.44274(1) nm). The crystal structure of CeZn7 was derived from the Rietveld refinement of X-ray
powder intensities. Precise data on atom site distribution and positional parameters have been
furthermore provided from X-ray single crystal refinements for two compounds, for which crystal
structures hitherto have only been derived from X-ray diffraction photographs: Ce3Zn11 (Immm,
a¼0.45242(2) nm, b¼0.88942(3) nm, c¼1.34754(4) nm) and Ce3Zn22 (I41/amd; a¼0.89363(2) nm,
c¼2.1804(5) nm).
Keywords:
Ce–Zn–B phase diagram
Ce–Zn system
Crystal structure
Ce3Zn11
Ce3Zn22
& 2011 Elsevier Inc. All rights reserved.
1. Introduction
2. Experimental
Zinc-based alloys with rare-earth metals are used in several
engineering applications and are often employed to replace cast
iron because of similar properties and better machinability [1].
Rare earths (RE) improve the mechanical performance, tensile
strength, hardness and also the corrosion resistance by removing
impurities from the grain boundaries of their alloys with zinc [2].
Zinc alloys with about 15 mass% boron or even less exhibit high
tensile strength, high degree of hardness, high resistance to
oxidation and corrosion, low shrinkage factor and low specific
gravity [3]. Multi-component zinc and boron alloys containing
various amounts of elements such as aluminium, copper or
calcium can be used for the production of bearings, bars, rods,
sheets, tubes, plates, for the production of ingots, or other finished
or semi-finished articles [3].
As far as high strength lightweight alloys for automotive
applications are concerned [4], the Ce–Zn system is an important
part of the multinary Mg-based alloy system Mg–Zn–Mn–RE,
however, nothing is yet known on the influence of boron addi-
tions and no phase diagrams have yet been reported for systems
RE–Zn–B. Therefore the present work tries to provide detailed
information on phase equilibria and crystal structures in the
Ce–Zn–B system.
Samples in a total amount of ca. 0.5 g each were prepared from
cerium ingots (Alfa Aesar, purity 499.9mass%), zinc granules (Alfa
Aesar, purity 499.9mass%) and boron pieces (ChemPur, Karlsruhe,
purity 98mass%). Zinc drops were purified in an evacuated quartz
tube by heating them below the boiling temperature of Zn (907 1C).
Cerium was mechanically surface cleaned before use.
2.1. Binary alloys
Ce cuttings and Zn filings in various stiochiometric ratios were
cold pressed, sealed in quartz tubes under vacuum and then slowly
heated to 420 1C. Samples were kept at this temperature for 12 h
before heating up to the melting range (about 100 1C above Tm) at
the rate of 1 1C/min prior to cooling down to 800 1C at the same rate.
The reguli were annealed at 800 1C for 7 days and quenched by
immersing the quartz ampoules in cold water. Selected alloys were
annealed at various temperatures in the range of 420 1C–850 1C for
7 days. CeB6 and CeBx master alloys were prepared by arc melting
cerium cuttings and boron pieces under argon.
2.2. Ternary alloys
Two procedures were used for the evaluation of ternary phase
relations:
n Corresponding author.
(i) samples were prepared from intimate blends of powders of
arcmelted CeBx master alloy and fine Zn-filings in proper
E-mail address: peter.franz.rogl@univie.ac.at (P. Rogl).
0022-4596/$ - see front matter & 2011 Elsevier Inc. All rights reserved.
doi:10.1016/j.jssc.2011.08.020

Z. Malik et al. / Journal of Solid State Chemistry 184 (2011) 2840–2848
2841
X-ray powder diffraction data were collected from each alloy in
as cast and annealed state employing a Guinier–Huber image plate
system with monochromatic CuKa1 radiation (81o2yo1001).
Quantitative Rietveld refinements of the X-ray powder diffraction
data were performed with the FULLPROF program [5].
compositional ratios. The blends were cold compacted in a
steel die without lubricant, vacuum sealed in quartz tubes
and heat treated and quenched as described for the binary
alloys.
(ii) samples were prepared from mixtures of arcmelted CeB6 and
binary CexZny master alloys prepared like described in (i).
Melting and heat treatment was performed as for alloys (i).
Single crystals were mechanically isolated from crushed as
cast alloys. Inspections on an AXS-GADDS texture goniometer
Table 1
Crystallographic data of unary and binary boundary solid phases of the system Ce–Zn–B.
Phase, temperature
Space group,
prototype
Lattice parameters (nm)
Comments
range (1C)
a
b
c
0.412
–
–
[10]
(
d
Ce)
Im3m
798–700 [10]
W
0rxr0.014 at 722 1C [10]
(
g
Ce)
0.51610
[10]
Fm3m
o726 [10]
Cu
(Zn)
P63/mmm
0.2665
0.4947
[10]
o420
Mg
0.2667(1)
0.4951(1)
From alloy Ce7Zn93, 600 1Ca
1.09251
2.38143
[13]
(bB)
R3m
o2092 [10]
ZnxB1ꢁx
–
–
–
–
b
–
B
–
–
0rxr0.042 at 907 1C [29]
x¼0 at 907 1C [29]
x¼0.042 at 907 1C [29]
x¼0.039 at 907 1C [30]
1.093
1.100
1.0986(2)
2.374
2.404
2.4016(4)
CeZn
0.3704(1)
[13]
Pm3m
o825 [10]
CsCl
0.37125(2)
0.37059(2)
850 1C [This work]a
830 1C Ce poor [This work]a
CeZn2
Immm
0.4633(5)
0.46393(8)
0.46356(4)
0.7538(5)
0.7544(1)
0.75375(7)
0.7499(5)
0.7506(1)
0.75525(6)
[13]
o875 [10]
CeCu2
700 1C Ce-rich [This work]a
850 1C Ce-poor [This work]a
CeZn3
Cmcm
0.4620(5)
0.46324(5)
0.4635(1)
1.0440(5)
1.0452(1)
1.0439(3)
0.6640(5)
0.66557(6)
0.6641(2)
[13]
o820 [10]
CeZn3
850 1C Ce-rich [This work]a
850 1C Ce-poor [This work]a
Ce3Zn11
Immm
0.45215
0.88855
1.3463
[13]
o840 [10]
La3Al11
0.45242(2)
0.45222(1)
0.45175(6)
0.88942(3)
0.88898(2)
0.8894(1)
1.34754(4)
1.34649(4)
1.3447(2)
Single crystal [This work]
820 1C Ce-rich [This work]a
820 1C Ce-poor [This work]a
Ce13Zn58
P63/mmc
1.4638(1)
1.4616(1)
1.4635(5)
1.4158(1)
1.4173(1)
1.4176(5)
820 1Cc [19]
820 1C Ce-rich [This work]a
820 1C [This work]a
o870 [10]
Gd13Zn58
CeZn5
P6/mmm
0.54163(5)
0.54082(1)
0.54163(5)
0.42647(5)
0.42798(1)
0.42647(5)
[13]
o885 [10]
CeZn5þy
CaCu5
800 1C Ce poor [This work]a
0.017ryr0.046 o885 1C [16]
Ce3Zn22
I41/amd
0.897(1)
2.133(5)
[17]
o960 [10]
Ce3Zn22
0.8936(2)
0.89331(2)
0.89286(1)
2.1380(5)
2.13701(6)
2.13599(2)
Single crystal [This work]
800 1C Ce-rich [This work]a
850 1C Ce-poor [This work]a
0.9090(5)
1.32844(7)
827 1C [13]
b
Ce2Zn17
R3m
o980 [10]
980-ꢀ750
[This Work]
Th2Zn17
0.90916(4)
0.90884(7)
0.90947(1)
1.32861(1)
1.3300(1)
1.32955(2)
850 1C [This work]a
850 1C Ce-rich [This work]a
750 1C Ce-poor [This work]a
a
Ce2Zn17
P63/mmc
Th2Ni17
TbCu7
0.9088(4)
0.8856(5)
[21]
o ꢀ750[This work]
0.52424(2)
0.44274(1)
700 1C [This work]a
CeZn11
I41/amd
1.0658(6)
1.06630(1)
1.0666(1)
1.06689(2)
0.6862(8)
497 1C [15]
o795 [10]
BaCd11
0.686644(7)
0.68645(1)
0.68680(2)
480 1C [This work]a
600 1C Ce rich [This work]a
600 1C Ce poor [This work]a
CeB4
P4/mbm
0.7208(1)
0.4091(1)
[13]
[13]
o2380 [10]
o2165 [14]
UB4
CeB6
0.4139(4)
Pm3m
o2550 [10]
o2330 [14]
CaB6
a
Quenching temperature of samples while the lattice parameters are measured at room temperature.

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Z. Malik et al. / Journal of Solid State Chemistry 184 (2011) 2840–2848
assured high crystal quality, unit cell dimensions and Laue
symmetry of the specimens prior to the X-ray intensity data
collections on a four-circle Nonius Kappa diffractometer equipped
with a CCD area detector employing graphite monochromated Mo
were refined with the SHELXL-97 program [7,8] within the
Windows version WINGX [9]. The as cast and annealed samples
were polished using standard procedures and microstructures
and compositions were examined by light optical microscopy
(LOM) and scanning electron microscopy (SEM) via Electron Probe
Micro-Analyses (EPMA) on a Zeiss Supra 55 VP equipped with an
Ka radiation (l¼0.071069 nm). Orientation matrices and unit cell
parameters were derived using the program DENZO [6]. No
absorption corrections were performed because of the rather
regular crystal shapes and small dimensions of the investigated
specimens. The structures were solved by direct methods and
EDX system operated at 20 kV. For binary compounds
bCe2Zn17
was used as EPMA standard. The differences between measured
and nominal compositions were found to be o1 at%.
Table 2a
Crystal structure dataa from X-ray single crystal evaluation of Ce3Zn11 and Ce3Zn22
.
Compound
Ce3Zn11
Ce3Zn22
Composition (at. %)c
Space group
Ce23.35Zn76.65
Immm; No. 71
La3Al11
Ce12Zn88
¯
I41/amd; No. 141, origin at 1
Structure type
Ce3Zn22
Ce3Zn22
Formula from refinement
Ce3Zn11
y
Range (deg)
2.74o
y
o36.16
2.47oyo36.26
Crystal size (
m
m)
20 ꢂ 30 ꢂ 45
0.45242(2)
0.88942(3)
1.34754(4)
25 ꢂ 30 ꢂ 45
0.89363(2)
0.89363(2)
2.13804(5)
a (nm)
b (nm)
c (nm)
Reflections in refinement
Mosaicity
615 Fo44
0.55
s
(Fo) of 759
875 Fo44
0.6
s(Fo) of 1131
Number of variables
28
39
2
RF
¼
S
9F20ꢁF2c9/
S
F02
0.026
5.6
0.021
6.7
RInt
GOF
1.059
0.0009(1)
1.061
Extinction (Zachariasen)
M1; Occ.
0.00011(1)
2a (0, 0, 0); 1.00 Ce2
8e(0, ¼, z); z¼0.25343(2); 1.00 Ce1
b
b
b
b
U
11; U22; U33; U23; U13; U12
M2; Occ.
11; U22; U33; U23; U13; U12
M3; Occ.
11; U22; U33; U23; U13; U12
M4; Occ.
11; U22; U33; U23; U13; U12
M5; Occ.
11; U22; U33;U23; U13; U12
M6; Occ.
11; U22; U33; U23; U13; U12
M7; Occ.
11; U22; U33; U23; U13; U12
0.0139(3); 0.0239(3); 0.0096(2); 0; 0; 0
4i (0, 0, z); z¼0.29571(2); 1.00 Ce1
0.0089(2); 0.0103(2); 0.0103(2); 0; 0; 0
0.0084(1); 0.0065(1); 0.0076(1); 0; 0; 0
4a (0, 3/4, 1/8); 1.00 Ce2
U
0.0066(1); 0.006(1); 0.0069(1); 0; 0; 0
8l (0, y, z); y¼ 0.35869(7), z¼0.34366(4); 1.00 Zn2
0.0119(3); 0.0109(3); 0.0166(3); 0; 0.002(2); 0
8l (0, y, z); y¼ 0.28363(7), z¼0.14007(4); 1.00 Zn1
0.0107(3); 0.0144(3); 0.0211(3); -0.0006(2); 0
4h (0, y, ½); y¼0.18232(10); 1.00 Zn3
0.0193(4); 0.0180(4); 0.0118(3); 0; 0; 0
2d (½, 0, ½); 1.00 Zn4
32i (x, y, z); x¼0.23223(4), y¼0.00749(4), z¼0.1889(2); 1.00 Zn1
0.0122(2); 0.0111(2); 0.0096(2); 0.0017(1); 0.0002(1); 0.0009(1)
16h (0, y, z) y¼0.02584(6), z¼0.37681(2); 1.00 Zn2
0.0091(2); 0.0147(2); 0.0119(2); -0.0021(2); 0; 0;
16h (0, y, z) y¼0.10292(6), z¼0.11676(2); 1.00 Zn3
0.0112(2); 0.0094(2); 0.0114(2); -0. 0012(2); 0; 0;
16h (0, y, z) y¼0.59875(6); z¼0.26315(2); 1.00 Zn4
0.0092(2); 0.0099(2); 0.0130(2); 0. 0017(2); 0; 0;
8c (0, 0, 0); 1.00 Zn5
U
U
b
U
b
b
U
0.0187(6); 0.0187(6); 0.0173(5); 0; 0; 0
U
0.0083(3); 0.0104(3); 0.0111(3); -0.0021(3); 0; 0
2.37; –1.33
Residual electron density; max;
min in [electrons/nm3] ꢂ 103
2.83; –1.85
a
Crystal structure data are standardized using the program Structure Tidy [31].
Anisotropic atomic displacement parameters Uij in (102 nm2).
b
c
Nominal composition of the alloy from which a single crystal was isolated.
Table 2b
Interatomic distances in Ce3Zn11
.
Atom
Distance (nm)
Atom
Distance (nm)
Atom
Distance (nm)
Ce1–4Zn1
Ce1–2Zn3
Ce1–4Zn2
Ce1–2Zn2
Ce1–2Zn1
Ce1–2Zn4
Ce1–Ce2
0.30935(4)
0.31950(5)
0.31975(4)
0.32550(6)
0.32806(6)
0.35631(3)
0.39848(3)
0.31506(6)
0.33369(4)
0.36195(7)
0.39848(3)
Zn1–2Zn2
Zn1–Zn4
Zn1–Zn2
Zn1–2Zn3
Zn1–2Ce1
Zn1–Ce2
Zn1–Ce1
Zn2–Zn2
Zn2–2Zn1
Zn2–Zn3
Zn2–Zn1
Zn2–2Ce1
Zn2–Ce1
Zn2–2Ce2
0.26014(4)
0.26956(6)
0.28236(7)
0.29616(4)
0.30935(4)
0.31506(6)
0.32807(6)
0.25137(12)
0.26014(4)
0.26266(7)
0.28236(7)
0.31975(4)
0.32550(6)
0.33369(4)
Zn3–2Zn2
Zn3–2Zn4
Zn3–4Zn1
Zn3–Zn3
0.26266(7)
0.27833(5)
0.29616(4)
0.32432(13)
0.31950(5)
0.36195(7)
0.26956(6)
0.27833(5)
0.35631(3)
Zn3–2Ce1
Zn3–2Ce2
Zn4–4Zn1
Zn4–4Zn3
Zn4–4Ce1
Ce2–4Zn1
Ce2–8Zn2
Ce2–4Zn3
Ce2–2Ce1

Z. Malik et al. / Journal of Solid State Chemistry 184 (2011) 2840–2848
2843
3. Results and discussion
The crystal data relevant to the unary and binary boundary
phases in the Ce–Zn–B system, including results of our reinves-
tigation of the Ce–Zn system, are presented in Table 1.
3.1. Binary boundary systems
The binary systems Zn–B and Ce–B were used in the version
presented by Massalski [10]. In agreement with literature data,
we observed no evidence of chemical interaction between zinc
and boron. The formation and crystal structures of compounds
CeB4 and CeB6 were confirmed. Although several critical assess-
ments have been recently published on the phases and phase
relations in the Ce–Zn binary [11,12], our work on the ternary
Ce–Zn–B system revealed several structural inconsistencies for
the binary Ce–Zn compounds [10,13,14], which made a reinves-
tigation of the crystal structures in the Ce–Zn binary system
necessary (see below).
Fig. 1. (a) Crystal structure of Ce3Zn11 (La3Al11-type) as an arrangement of
building blocks of AuCu3-and BaAl4-type and (b) Coordination polyhedra for all
crystallographic sites in Ce3Zn11 with anisotropic displacement ellipsoids from
single crystal refinement.
Fig. 2. Unit cell of Ce3Zn22 revealing the coordination polyhedra around atom sites
for Ce1 and Ce2. Anisotropic displacement parameters comply with single crystal
refinement.
Table 2c
Interatomic distances in Ce3Zn22
.
Atom
Distance (nm)
Atom
Distance (nm)
Atom
Distance (nm)
Ce1–2Zn4
Ce1–2Zn3
Ce1–2Zn2
Ce1–4Zn1
Ce1–2Zn2
Ce1–4Zn1
Ce1–2Zn2
Ce2–4Zn3
Ce2–4Zn4
Ce2–8Zn1
Ce2–4Zn5
Zn1–Zn2
Zn1–Zn1
Zn1–Zn5
Zn1–Zn3
Zn1–Zn1
Zn1–Zn4
Zn1–Zn2
Zn1–Zn4
Zn1–Zn3
Zn1–Ce1
Zn1–Ce2
Zn1–Ce1
0.3124(1)
0.3204(1)
0.3251(1)
0.3303(1)
0.3312(1)
0.3456(1)
0.3661(1)
0.3159(1)
0.3248(1)
0.3386(1)
0.3483(1)
0.2571(1)
0.2633(1)
0.2651(1)
0.2722(1)
0.2750(1)
0.2771(1)
0.2779(1)
0.2780(1)
0.2805(1)
0.3303(1)
0.3386(1)
0.3456(1)
Zn2–2Zn1
Zn2–Zn4
Zn2–2Zn1
Zn2–2Zn3
Zn2–2Zn2
Zn2–Ce1
Zn2–Ce1
Zn2–Ce1
Zn3–Zn3
Zn3–Zn5
Zn3–2Zn1
Zn3–2Zn2
Zn3–2Zn1
Zn3–2Zn4
Zn3–Ce2
Zn3–Ce1
Zn3–Zn4
0.2571(1)
0.2673(1)
0.2779(1)
0.2802(1)
0.2834(1)
0.3251(1)
0.3312(1)
0.3661(1)
0.2629(1)
0.2660(1)
0.2722(1)
0.2802(1)
0.2806(1)
0.2909(1)
0.3158(1)
0.3204(1)
0.3611(1)
Zn4–2Zn5
Zn4–Zn2
Zn4–Zn4
Zn4–2Zn1
Zn4–2Zn1
Zn4–2Zn3
Zn4–Ce1
Zn4–Ce2
Zn4–Zn3
Zn5–4Zn4
Zn5–4Zn1
Zn5–2Zn3
Zn5–2Ce2
0.2626(1)
0.2673(1)
0.2703(1)
0.2771(1)
0.2780(1)
0.2909(1)
0.3123(1)
0.3218(1)
0.3611(1)
0.2626(1)
0.2651(1)
0.2660(1)
0.3483(1)

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Z. Malik et al. / Journal of Solid State Chemistry 184 (2011) 2840–2848
3.2. The system Ce–Zn
for those compounds (hexagonal-CeZnꢀ7, rhombohedral-Ce2Zn17,
Ce3Zn22, Ce13Zn58, and Ce3Zn11), for which crystal structure data
hitherto have only been derived from X-ray diffraction photo-
graphs or have not been evaluated (hex-CeZnꢀ7).
Crystal structure Rietveld refinements for all those binary
compounds, which have been already reported earlier, namely
CeZn11 [15], CeZn5, CeZn3, CeZn2 and CeZn [10,13], were found to
be consistent with data in the literature. Therefore, the reinves-
tigation of crystal structures and phase relations in the Ce–Zn
system essentially focused on the determination of crystal sym-
metry, precise atom site distribution and positional parameters
3.2.1. Structural chemistry
3.2.1.1. X-ray single crystal intensity data refinement of Ce3Zn11 and
Ce3Zn22
.
Ce3Zn11: The X-ray intensity spectrum of a single crystal selected
from the crushed sample Ce23.35Zn76.65 (at%) was fully indexed with
an orthorhombic lattice (a¼0.45242(2) nm, b¼0.88942(3) nm,
c¼1.34754(4) nm). Systematic extinctions only observed for a
body-centred Bravais lattice (hkl), hþkþl¼2nþ1 indicated the
space groups Immm, I222, Imm2 and I212121. Immm with highest
symmetry was used to solve the crystal structure employing direct
methods. Composition, lattice parameters, crystal symmetry,
Wyckoff sequence 2a, 2d, 4h, 4i, 8l2 and atom parameters
prompted isotypism with the structure type of La3Al11
.
The
structure solution converged at RF2 ¼ꢁ 2.6 yielding
a residual
3
˚
electron density less than 72.8 e /A . Crystal data and
interatomic distances are presented in Tables 2a and 2b. The
characteristic stacking of face-connected unitsyAuCu3–BaAl4 yis
documented in Fig. 1 including the polyhedra of the individual atom
sites. Although the structure solution provides positional and
thermal atom parameters of significantly higher precision it
confirms the early structure determination of Ce3Zn11 by Lott and
Chiotti [16] performed on the basis of X-ray Weissenberg and
precession photographs.
Fig. 3. X-ray powder spectrum of alloy Ce10Zn90 and Rietveld refinement of the
low temperature phase: hexagonal CeZn7 (Ce1ꢁxZn5þ2x, x¼0.33) with TbCu7-type.
(Excluded region contains a small peak from sample holder).
Ce3Zn22: The first analysis of the crystal structure of Ce3Zn22
from essentially steric considerations is due to Kripyakevich et al.
Table 3a
Rietveld refinement data for Ce13Zn58, Ce1ꢁxZn5þ2x-hex; (x¼0.33; aCeZn7) and alloy Ce8.6Zn70.7B20.7 (all from GuinierꢁHuber Image Plate, CuKa1).
Compound
Ce13Zn58
Ce1ꢁxZn5þ2x-hex; (x¼0.33)
Ce2Zn17-rhombohedral
Nominal composition (at%)
Composition from EPMA
Space group
Ce18.31Zn81.69
Ce18.0Zn82.0
Ce10Zn90
Ce8.6Zn70.7B20.7
Ce11.08Zn88.92
–
P63/mmc; No. 194
P6/mmm; No. 191
R3m; No. 166
Th2Zn17
Structure type
Ce13Zn58
TbCu7
Composition from refinement
Theta range
Ce16.3Zn82.7
Ce10.6Zn89.4
Ce10.5Zn89.5
81o2
y
o1001
81o2
y
o1001
81o2yo1001
0.90872(1)
1.32825(2)
146
a (nm)
1.4616(1)
1.418(1)
606
0.52424(2)
0.44274(1)
39
c (nm)
Reflections in refinement
No. of parameters refined
Reliability factors
103
26
39
RF¼
S
jFoꢁFcj/
S
Fo
0.032
0.045
0.038
Rexp¼[(NꢁPþC)/
w2¼(RwP/Re)2
R1; Occ.; Biso
S
(wiy2oi)]1/2
0.032
0.035
0.024
11.2
5.84
4.15
12k (x, 2x, z); x¼0.2031(4),
1a (0, 0, 0); 0.67(3) Ce1; 0.29(2)
6c (0, 0, z); z¼0.33561(7);
1.00(1) Ce1; 0.32(2)
z¼0.0529(3); 0.888(2) Ce1; 0.85(5)
x¼0.5057(9); 0.448(2) Ce2; 0.4(1)
x¼0.875(4); 0.486(1) Ce3; 0.8(1)
0.924(2)Ce4; 0.7(2)
R2 in 6h (x, 2x, ¼); Occ.; Biso
R3 in 6h (x, 2x, ¼); Occ.; Biso
R4 in 2a (0, 0, 0); Occ., Biso
M1; Occ.; Biso
24l (x, y, z); x¼0.3725(4), y¼0.0374(5),
z¼0.0992(5); 0.948(8) Zn1; 0.9(1)
12k (x, 2x, z); x¼0.0923(7),
3g (½, 0, ½); 1.00(1) Zn1; 0.15(3)
18h (x,x ,z); x¼0.5052(4),
z¼0.15512(7); 1.00(1) Zn1; 0.20(2)
M2; Occ.; Biso
M3; Occ.; Biso
M4; Occ.; Biso
2e (0,0, z); z¼0.2995(5); 0.33(1) Zn2; 0.43(2) 18f (x, 0.0); x¼0.29213(9);
z¼0.1548(6); 0.868(6) Zn2; 0.9(1)
12k (x, 2x, z); x¼0.247(2),
1.00(1) Zn2; 0.20(3)
2c (1/3, 2/3, 0); 1.00(1) Zn3; 0.46(3)
9d (½, 0, ½); 1.00(1) Zn3; 0.53(4)
z¼0.6724(6); 0.858(8) Zn3; 0.8(2)
12k (x, 2x, z); x¼0.549(2),
6c (0.0,z); z¼0.0988(1);
1.00(1) Zn4; 0.67(4)
z¼0.6332(7); 1.00(1) Zn4; 0.3(2)
x¼0.5995(9), z¼0.0521(7); 1.00(1) Zn5; 0.8(1)
x¼0.0910(7), y¼0.3728(7); 0.958(5) Zn6; 0.2(1)
x¼0.194(3); 0.552(5) Zn7; 0.3(3)
x¼0.2701(5), 1.00(1) Zn8; 0.4(2)
0.640(4) Zn9; 0.9(3)
M5 in 12k (x, 2x, z); Occ., Biso
M6 in 12j (x, y, ¼); Occ., Biso
M7 in 12i (x, 0, 0); Occ., Biso
M8 in 6h (x, 2x, ¼); Occ., Biso
M9 in 6g (½, 0, 0); Occ., Biso
9e (½, 0, 0); 0.15(4)B; 0.8(–)
M10 in 4f (1/3, 2/3, z); Occ., Biso z¼0.095(1); 0.882(3) Zn10; 0.3(3)
M11 in 2d (1/3, 2/3, 3/4); Occ., Biso 0.912(2) Zn11; 0.08(48)
M12 in 2b (0, 0, ¼); Occ., Biso
0.924(2) Zn12; 0.3(5)

Z. Malik et al. / Journal of Solid State Chemistry 184 (2011) 2840–2848
2845
[17] providing a set of atom parameters. Johnson and Wood [18]
compared observed and calculated X-ray powder data for Ce3Zn22
and reported isotypism with the structure of Pu3Zn22 for which
they solved the structure on the basis of single crystal Weissenberg
and precession photographs (reliability factor RF¼0.096). In order
to provide a precise set of atom parameters and to check on defects
or random distributions, a full structure determination was per-
formed on a crystal selected from a crushed sample with nominal
composition Ce12Zn88 (at%). X-ray intensity data depicted systema-
tic extinctions, (hkl) for hþkþl¼2nþ1, (hk0) for h,k¼2nþ1 and
(hhl) for 2hþl¼4nþ1 prompted space group I41/amd as the one
with highest symmetry. Structure analysis employing direct meth-
ods ended up at RF2 ¼ 2.1 and residual electron densities less than,
of the A-atoms is randomly or in ordered fashion replaced by a
dumbbell of B-atoms covering a range of stoichiometries AB5 to
AB9.5 [25]. Rietveld refinement of the ‘‘aCe2Zn17’’ pattern on the
basis of this model prompted a low residual value RF¼0.045 with a
random distribution of 0.67 Ce in the 1a site of space group
P6/mmm, the holes around the vacancies being filled by 0.33 Zn-
dumbbells (Zn2) in site 2e. Accordingly the overall formula is close
to Ce0.7Zn5.6 (Ce1–xZn5þ2x; xꢀ0.33).
The Rietveld refinement profile for aCeZn7 is shown in Fig. 3.
Interatomic distances are depicted in Table 3a, 3b and Fig. 4a.
A Fourier map (Fig. 5b) shows the presence of the electron
density, which refers to the Zn2 atoms. Formally short distances
dCe–Zn2¼0.133 nm and dZn2–Zn2¼0.174 nm appear for the random
occupation of Ce and Zn2 atoms. However, either a Ce-atom
ꢁ
3
˚
72.4 e /A . The refinement with anisotropic ADPs revealed a fully
ordered structure without any defect atom sites. Crystal data and
interatomic distances are presented in Tables 2a and 2c, respec-
tively. The crystal structure of Ce3Zn22 is shown in Fig. 2 in three-
dimensional view on the bc plane emphasizing on the interconnec-
tivity of the Ce-centred polyhedra (Ce1 polyhedra with coordination
number 18 and Ce2 polyhedra with coordination number 20).
Description of the structure, coordination polyhedra and intera-
tomic distances are consistent with the description earlier pre-
sented for isotypic Pu3Zn22 [18].
or
a Zn2-dumbbell may exist with an acceptable distance
dCe–Zn2¼0.300 nm and dZn2–Zn2¼0.260 nm.
Table 3b
Interatomic distances for Ce1ꢁxZn5þ2x-hex; (x¼0.33).
Atom
Distance (nm)
Atom
Distance (nm)
Ce1–2Zn2
Ce1–6Zn3
Ce1–2Zn2
Ce1 –12Zn1
Zn1–4Zn1
Zn1–4Zn3
Zn1–4Zn2
Zn1–Ce1
0.13234
0.30258
0.31027
0.34299
0.26204
0.26807
0.27673
0.34299
Zn2–Ce1
Zn2–Zn2
Zn2–Zn2
Zn2–6Zn1
Zn2–Ce1
Zn2–6Zn3
Zn3–6Zn1
Zn3–Ce1
Zn3–Zn3
Zn3–2Ce1
Zn3–2Zn3
Zn3–6Zn2
0.13234
0.17793
0.26468
0.27673
0.31027
0.33025
0.26807
0.30258
0.30258
0.30258
0.30258
0.33025
3.2.1.2. Rietveld refinement of Ce13Zn58, rhombohedral
and of hexagonal CeZn7 (lT).
bCe2Zn17 (hT)
a
Ce13Zn58: Recently single crystal studies were reported for the
RE13Zn58 family of hexagonal quasicrystals derived from Gd13Cd58
(RE¼Ce, Pr, Nd, Sm, Gd, Tb, Dy) [19]. Whereas the Ce and Pr
structures were reported to be identical to the prototype,
different types of disorder were detected for the other members
of the series. Our X-ray powder refinement of Ce13Zn58 revealed
significant defects for several atom positions e.g. for the sites Ce3,
Zn3 and Zn9. With respect to the formation of periodic structures
for the later members of the rare earth series, we assume that the
structure of Ce13Zn58 may exhibit a similar variability in local
ordering rendering the general formula Ce13Zn58
.
Rhombohedral Ce2Zn17: Polymorphism was reported for the
b
compound Ce2Zn17 with a rhombohedral structure at high tem-
peratures but a hexagonal structure at low temperature [20,21]. In
agreement with the findings in the literature our X-ray powder
spectra obtained from samples annealed at 800 1C were fully
indexed on the basis of a rhombohedral lattice (a¼0.90916(4) nm,
c¼1.3286(1) nm) prompting isotypism with the structure type of
Th2Zn17 (space group R3m; No. 166). The results of the Rietveld
refinement confirm the Th2Zn17–type as defined earlier for a single
crystal study of the high temperature modification of Ce2Zn17 [22].
Hexagonal aCeZn7 (aCe2Zn17): As already observed by Iandelli
and Palenzona [21], it seems extremely difficult to obtain the low
temperature form from the high temperature modification
(bCe2Zn17) by long term annealing at 500 1C. bCe2Zn17 however,
can easily be formed by heating the low temperature modification
above ꢀ775 1C. Slow heating of the mixture of components
Ce10.5Zn89.5 (at%) up to 500 1C and annealing at this temperature
for 5 days produced an alloy with an X-ray powder diffraction
pattern yielding a majority of the low-temperature phase. Although
the X-ray pattern was completely indexed with an hexagonal cell
(a¼0.52424(2) nm, c¼0.44274(1) nm) for the low temperature
form and small amounts of
(BaCd11-type), the small unit cell parameters do not correspond to
the Th2Ni17-type structure as reported for ‘‘ Ce2Zn17’’ by Iandelli
bCe2Zn17 (P63/mmc) and CeZn11
a
and Palenzona [21] and Veleckis et al. [23]. Much better correspon-
dence between the observed and calculated X-ray powder diffrac-
tion patterns was achieved applying the atomic model of the TbCu7
type structure [24]. The TbCu7-type adopts the CaCu5-type unit cell
and is a member of a structure family A1ꢁsB5þ2s where a fraction s
Fig. 4. (a) Crystal structure of hexagonal CeZn7 [Ce1ꢁxZn5þ2x (x¼0.33)] with
TbCu7-type. A Zn-dumbbell replaces the Ce-atom site in the left lower front
corner. (b) Fourier map for hexagonal CeZn7 projected onto the yz plane revealing
the Zn-dumbbells.

2846
Z. Malik et al. / Journal of Solid State Chemistry 184 (2011) 2840–2848
3.2.2. The phase diagram Ce–Zn
modelings of the binary system [11,12], both relying on the experi-
mental solidus and liquidus data and the reaction isotherms deter-
mined by Chiotti and Mason [26]. In accordance with the published
Ce–Zn phase diagram our X-ray reinvestigation confirmed the
existence of all compounds hitherto reported. For a listing of crystal
data of compounds (unit cell parameters, space group and structure
type) see Table 1. Whereas the crystal structures of CeZn11, CeZn5,
CeZn3, CeZn2 and CeZn, were found to be consistent with data in the
literature (Table 1), precise structural data on atom site distribution,
atom order and defect formation were provided for hexagonal-CeZn7,
Ce3Zn22, Ce13Zn58, and Ce3Zn11 (for details see Section 3.2.1). We also
confirm the irreversible character of the transition (about 750–
800 1C on heating) between the low temperature form CeZn7
Knowledge on the binary Ce–Zn phase diagram is summarized in
two recent critical assessments and Calphad-type thermodynamic
(Ce10Zn90 at%) and the high temperature form
n
b
b
Ce2Zn17 (Ce10.6Z-
89.4 at%), both existing at practically identical composition. Once
Ce2Zn17 has formed it is impossible to revert to CeZn7 ( Ce2Zn17),
a
a
an observation already reported in earlier studies [21].
Evaluation of homogeneity regions of the binary compounds
with respect to lattice parameter and EPMA data generally
confirmed the various Ce-zincides as practically line-compounds
without significant phase regions. Fig. 5 documents the two-
phase regions for the boundary phases. There was no difference
between the refined and reported lattice parameters of Zn [27]
suggesting no solubility of Ce in Zn.
3.3. The system Ce–Zn–B (o50 at% Ce)
About 20 ternary alloys were prepared and analyzed by X-ray
powder diffraction combined with EPMA. The analysis of the
isothermal section at 800 1C did not reveal the formation of
ternary compounds and all three-phase equilibria derived are
documented in Table 4. Two-phase equilibria between CexZny
binaries and CeB4 range from CeZn to Ce3Zn22, whereas Ce2Zn17
and CeZn11 tie to CeB6 (see Fig. 6). In order to verify the equilibria a
set of samples was made from CeB6þCeZnx master alloys, which on
formation of CeB4 for (2oxo7) confirmed the triangulation in Fig. 6.
Rietveld refinements of representative alloys are summarized in
Fig. 7 and document that no ternary Ce–Zn–borides were observed in
Fig. 5. Microstructures for selected Ce-Zn samples annealed at 800 1C for 7 days:
(a) 40 at.%Ce, (b) 29 at.% Ce, (c) 20 at% Ce, (d) 17.6 at%, (e) 14.3 at.% Ce and
(f), 11.27 at.% Ce.
Table 4
Phase analyses (EPMA and XPD) of Ce–Zn–B alloys, annealed at 800 1C.
Code
a
Nominal composition
Ce–Zn–B (at%)
Experimental
Phase
Space group
Structure type
Lattice parameters (nm)
a
b
c
8–72–20
CexBy
(ArcMelted)þ
Zn
CeZn11
Ce2Zn17
I41/amd
R3m
BaCd11
Th2Zn17
1.06589(6)
0.908727(6)
–
–
0.68602(9)
1.32822(1)
CeB6
CaB6
0.4149(1)
–
Pm3m
b
c
d
e
f
17–50–33
19–45–36
20–70–10
22–69–9
CexBy
Ce3Zn22
CeZn5
CeB4
I41/amd
P6/mmm
P4/mbm
Ce3Zn22
CaCu5
UB4
0.89339(2)
0.541078(9)
0.72085(1)
–
–
–
2.13793(6)
0.42778(1)
0.409173(8)
(ArcMelted)þ
Zn
CexBy
CeZn5
Ce13Zn58
CeB4
P6/mmm
P63/mmc
P4/mbm
CaCu5
Gd13Cd58
UB4
0.541716(7)
1.46306(9)
0.72076(1)
–
–
–
0.427091(8)
1.4171(1)
0.409129(8)
(ArcMelted)þ
Zn
CeB6
(ArcMelted)þ
CexZny
Ce13Zn58
Ce3Zn11
CeB4
P63/mmc
Immm
P4/mbm
Gd13Cd58
La3Al11
UB4
1.46278(2)
0.45210(2)
0.7209(1)
–
1.4163(2)
1.34685(8)
0.4048(1)
0.88854(5)
–
CeB6
(ArcMelted)þ
CexZny
Ce3Zn11
CeZn3
CeB4
Immm
Cmcm
P4/mbm
La3Al11
CeZn3
UB4
0.45260(2)
0.46338(4)
0.72564(4)
0.89027(4)
1.0460(1)
–
1.34753(7)
0.66440(6)
0.40312(4)
28–62–10
CeB6
(ArcMelted)þ
CexZnv
CeZn3
CeZn2
CeB4
Cmcm
Imma
P4/mbm
CeZn3
CeCu2
UB4
0.46352(7)
0.4673(1)
0.7207(6)
0.41418(2)
1.0457(2)
0.7512(8)
–
–
0.6650(1)
0.7557(1)
0.4090(6)
–
Unreacted
CeB6
CaB6
Pm3m
g
43–37–20
CeB4
(ArcMelted)þ
CexZny
CeZn2
CeZn
Imma
CeCu2
CsCl
0.46422(3)
0.37087(2)
0.75427(6)
–
0.75080(6)
–
Pm3m
P4/mbm
CeB4
UB4
0.72022(6)
–
0.40860(6)

Z. Malik et al. / Journal of Solid State Chemistry 184 (2011) 2840–2848
2847
the alloys investigated. It is, however, still unclear whether Ce2Zn17
ties to CeB4 or Ce3Zn22 ties to CeB6 (dashed line in Fig. 6).
In analogy to carbon incorporation in the Th2Zn17 type
structure of Pr2Mn17C3–x [28] we tested the solubility of boron
as interstitial in Ce2Zn17 for alloy Ce8.6Zn70.7B20.7 (in at%). Rietveld
refinement of the powder pattern, however, revealed no change
in the lattice parameters with respect to binary Ce2Zn17 as well as
the absence of B in the octahedral voids [Ce2Zn4]. The interatomic
distances dB–Ce¼0.262 and dB–Zn¼0.189 nm are unfavourable to
form Ce2Zn17B3–x. The evaluation of the Rietveld refinement is
shown in Table 3a and Fig. 7d.
4. Conclusion
With EDX and WDX-electron microprobe analysis and X-ray
powder diffraction we have derived the isothermal section for the
system Ce–Zn–B at 800 1C. The section is characterized by the
absence of ternary compounds and the absence of significant
mutual solid solubilities of binary phases. In the course of
the ternary system investigation the binary Ce–Zn system was
re-evaluated on about 20 alloys. In the concentration range of
Fig. 6. Ce-Zn-B. Isothermal section at 800 1C.
Fig. 7. Rietveld refinement for alloys (a) Ce43Zn37B20, (b) Ce19Zn45B36, (c) Ce16.7Zn50B33.3 and (d) Ce8.6Zn70.7B20.7. (Excluded regions in 7a ad c contain a small peak from
sample holder).

2848
Z. Malik et al. / Journal of Solid State Chemistry 184 (2011) 2840–2848
10–10.5 at% Ce two structural modifications have been confirmed,
which show irreversible transformation behaviour: high temp-
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b
Ce2Zn17 exists above ꢀ750 1C with the Th2Zn17 type
(R3m, a¼0.90916(4) nm, c¼1.3286(1) nm) and low temperature
CeZn7 (Ce1–xZn5þ2x; xꢀ0.33) adopts the TbCu7 type (Rietveld
refinement of X-ray powder data; P6/mmm, a¼0.52424(2),
c¼0.44274(1) nm), which irreversibly transfers to the hT phase
on heating above 750 1C. X-ray single crystal refinements have
been carried out for several compounds, for which crystal structure
data hitherto have only been derived from X-ray diffraction
photographs. Thus precise data on atom site distribution and
positional parameters have been provided for Ce3Zn11 (Immm,
a¼0.45242(2), b¼0.88942(3) and c¼1.34754(4) nm) and Ce3Zn22
(I41/amd, a¼0.89363(2) and c¼2.1804(5) nm).
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Acknowledgments
The research reported herein was supported by the Higher
Education Commission of Pakistan (HEC) under the scholarship
scheme ‘‘PhD in Natural & Basic Sciences from Austria’’. We thank
to Dr. S. Puchegger for his expert assistance in EPMA measurements.
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