R624
Philips Res. Repts 22, 233-245, 1967
SYSTEMATIC ARRANGEMENT OF THE BINARY
RARE-EARTH-ALUMINIUM SYSTEMS *)
by K. H. J. BUSCHOW and J. H. N. van VUCHT
Abstract
A number of binary rare-earth-aluminium systems were investigated by
X-ray diffraction and thermoanalytical methods. It is shown that both
the stability and composition of the intermetaIlic compounds found in
these systems are strongly influenced by the atomic size ofthe rare-earth
metals (R). If these binary systems are arranged in order of decreasing
radius it appears that a compound R3AI exists only for rare-earth metals
with relatively large radius. With decreasing radius, a compound R2Al
is also observed. It becomes gradually more stable, while R3Al disappears. For still smaller radii a compound R3Al2 is found in addition
to R2Al. The compounds RAl and RAl2 exist for almost all rare-earth
metals investigated. Here, however, some interesting relationships exist
between the decreasing radius and the crystal structures of the compounds. Between RAl2 and aluminium the compounds RAl3 and
R3AIll are found; RAl3 is relatively more stable for small radii and
R3Alll for large radii. The compound RAl3 was observed for all rareearth metals investigated except for europium; its crystal structure shows
again a remarkable dependence on the radius of the rare-earth metal.
1. Introduction
The rare-earth-aluminium systems provide a very useful series for studying
the influence of the size of the metallic radius of one component in binary
systems. We have therefore investigated eight of the most revealing rare-earthaluminium systems using thermoanalytical metallographic and X-ray-diffraction methods. As yttrium is closely related to the rare-earth metals the
yttrium-aluminium system, investigated by Lundin and Klodt 1), has been
added. A good understanding of the mutual differences of the rare-earthaluminium phase diagrams and the crystal structures of the intermetallic compounds is obtained if the rare-earth elements are arranged in order of their
decreasing radii. From the lattice constants of the compounds Y 2Al, Y 3Al2 2)
and YAl2 3) compared with those of the corresponding compounds of the
lanthanides it can be derived that yttrium is best arranged between the elements
gadolinium and terbium.
The alloy samples used for the study of the given phase diagrams have been
prepared by arc-melting. The purity of the starting materials was 99·99 % for
aluminium and 99·9 % for the rare-earth metals except for erbium and samarium,
which had a purity of 99·6 % and 99·0 %, respectively. For some of the samar.ium-aluminium intermetallic compounds different crystal structures have been
"') Apart from many new data this paper has been presented at the 5th Rare Earth Research
Conference, held at Ames (Iowa) in September 1965.
I.
234
K. H. J. BUSCHOW and J. H. N. van VUCHT
reported in literature 4.5), and therefore these compounds were reinvestigated
with samarium of 99·9 % purity. The results were, however, the same.
2. Results and discussion
In fig. 1 the equilibrium diagrams between aluminium and seven rareearth metals are given. The equilibrium
diagram of the system yttriumaluminium
as given by Lundin and Klodt 1) is also given. The binary
systems AI-Tb, Al-Dy and Al-Ho have .not been investigated thermoanalytically. Frommicroscopical
and Xsray-diffractional investigations it became clear,
however, that the situations in these phase diagrams will be analogous to those
of the system Y-Al or Er-AI; this is also what might be expected, sin~e the
metallic radii of Tb, Dy and Ho are intermediate to those of Y and Er. For the
element Eu only a few aluminium-rich compounds could be prepared; they will
be discussed at the proper place. The elements samarium and ytterbium possess
exceptionally low heats of sublimation and high vapour pressures as compared
to the other rare-earth metals 6). These facts present serious difficulties regarding the thermoanalytical
investigations of alloy buttons of the corresponding
binary systems with aluminium. For the samarium-aluminium
system reliable
thermoanalytical
data could be obtained only below 1100 oe (see also ref. 7).
The ytterbium-aluminium
system has only been investigated by X-ray diffraction. As serious ytterbium losses occurred when the ytterbium-aluminium
alloys
were prepared by arc-melting these metals were molten together in a sintered
Al203 crucible under carefully controlled conditions in a high-frequency
furnace. When annealing proved necessary the Al203 crucible containing the
sample was closed by means of a foil of tantalum metal and tantalum wire and
the whole sealed into an evacuated silica container. In this way the loss ofytterbium metal from the melt was greatly reduced while it seemed unlikely that the
melt was contaminated by gaseous silicon compounds that might possibly be
formed by the reaction of silica with sublimed ytterbium at the container wall.
Subsequent X-ray analyses of the samples showed that no intermediate phase
occurs up to approximately 67 at. % aluminium; annealed and as-cast samples
when subjected to X-ray diffraction only gave rise to refiexions belonging to
ytterbium metal and the Laves-phase compound YbAI2. The compound YbAl3
was the only one observed between YbAl2 and aluminium metal. Both compounds melt fairly high (> 1000 0C). If the results obtained for the ytterbiumaluminium systems are compared with those obtained for the other R-aluminium systems (fig. 1) it is clear that this phase diagram does not fit in the
sequence of R-aluminium diagrams arranged according to the size of the rareearth component. Magnetic measurements have shown that ytterbium is trivalent in Yb Al, 8); in the trivalent state it is smaller than erbium so that one would
expect a phase diagram of the type observed for the other rare-earth metals.
This is indeed found experimentally at the aluminium-rich side (> 67 at. % Al)
SYSTEMATIC ARRANGEMENT
OF THE BINARY RARE-EARTH-AI
SYSTEMS
23S
of the ytterbium-aluminium
diagram. From the lattice constant (a = 7·875 A)
and the magnetic behaviour of the compound YbAl2 it can be deduced that
Yb is divalent in this compound 9). In this state the Yb radius exceeds that of
La. Furthermore
the valence-electron concentration
of a Yb compound will
then be much lower than that of the corresponding compound with a normal
trivalent rare-earth metal. This might explain the rather surprising fact that no
additional compounds are observed between YbAl2 and ytterbium metal. In
this connection we want to point out that the divalent metal Ca (metallic radius
1·96 A) forms a constitutional
diagram with Al which has the same shape as
that formed by Yb and Al, provided that only those concentration regions are
considered where Yb is supposed to be divalent (atomic radius 1·95 A).
Solid solubility R(Al)
From X-ray data it could be shown that the solubility of aluminium in the
lattice of the rare-earth metals is in general very poor, but it seems to increase
with decreasing rare-earth radius. Within the accuracy of the thermoanalytical
data (± 5 "C) there .was no detectable influence of aluminium on the transformation temperature of the rare-earth metals.
R3Al
In the present investigation a compound R3Al has only been observed for the
elements at the beginning of the lanthanide group, viz. La, Ce, Pr and Nd. As
has been shown previously 10), the compound Ce3Al consists of a high-temperature modification which has the cubic CU3Au type of structure and a lowtemperature modification of the hexagonal Ni3Sn type. The same behaviour is
found for Pr3Al, while La3AI and Nd3AI are isotypic with a-Ce3Al and a-Pr3AI
(Ni-Sn-type). For these compounds no phase transformation
was found.
The cubic modification of the R3AI compounds (which has been observed
only for cerium and praseodymium)
has the Cu3Au structure in which the
minority atom is the relatively small aluminium while the large majority atoms,
determining the dimensions of the' unit cell, form a sizable octahedral hole
which may accomodate atoms such as C, N or 0. The structures arising in this
manner are usually referred to as perovskites: It seems likely that the cubic
modification of the R3AI compounds may be stabilized by incorporating the
foreign atoms mentioned, even when only a very small fraction ofthe octahedral
holes are filled. In the latter case an additional reduction ofthe free energy arises
from the enhanced entropy, especially at high temperatures.
Since oxygen is
always present in the alloys as an oxide (A1203 or R203) one might wonder
if the phase transformations
observed for Ce3AI and Pr3AI originate from a
stabilization of the cubic form. For carbon atoms the stabilization has been
found experimentally to be rather strong. By adding carbon to the melt the
cubic form of R3Al has been obtained for almost all rare-earth elements, viz.
236
K. H. J. BUSCHOW and J. H. N. van VUCHT
for Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er. Under normal conditions the last
six elements even do not form a compound R3Al. The lattice constants for these
compounds are given in table I. Similar attempts to stabilize the cubic phase
TABLE I
compound
latticeconstant a CA)
Ce3AIC"
Pr3AlC"
Nd3AIC"
Sm3AlC"
Gd3AlC"
Tb3AlC"
DY3AlC"
H03AlC"
Er3AlC"
Y3AIC"
5·007
5·040
5·003
4·940
4·891
4·864
4·842
4·809
4·783
4·854
R3AI by incorporating nitrogen atoms were unsuccessful. It is to be expected
that the elements C, Nand 0, when incorporated in these alloys, take on
effectively a metallic character and that this is more easily achieved by carbon
atoms than by nitrogen atoms. Especially for oxygen atoms this behaviour does
not agree with their chemical nature. From the experimental fact that even
nitrogen does not succeed in stabilizing the cubic form of R3AI it may be
infe~red that the phase transformations observed for Ce3Al and Pr3AI are
properties belonging to the pure binary compounds, i.e. they are not due to
any stabilization of the cubic form by oxygen incorporation. A carbon .content
has not been detectable.
R2AI
.It can be seen from the figures that the compound richest in rare-earth metal
changes in the course of the series from R3Al to R2Al. Both types of compounds
are found to exist adjacent to each other in the systems Pr-AI and Nd-Al. From
samarium on, only the compound R2Al seems to be stable. In addition to the
rare-earth metals shown in the figures a compound R2Al has furthermore been
observed for terbium, dysprosium and holmium. The X-ray powder diagrams
of these compounds are all isotypic and have tentatively been indexed orthorhombically. The lattice constants are given in table Il. The value given for
H02AI agrees well with that given by Meyer 11).
. The fact that landelli 4) observed a compound R3Al instead of R2AI for
SYSTEMATIC
ARRANGEMENT
OF THE BINARY
RARE-EARTH-Al
237
SYSTEMS
TABLE II
lattice constants
compound
Pr2Al
Nd2Al
Sm2Al
Gd2AI
Y2AI
Tb2Al
DY2AI
HÖ2AI
Er2AI
CA)
a
b
c
7·872
7·848
7·782
7·69
7·62
7·66
7·59
7·570
7·523
9·461
9·395
9·302
9·24
9·22
9·18
9·13
9·150
9·056
11·45
11·38
11·21
11·21
11·14
11·07
11·04
10·965
10·925
samarium is not at all surprising since it follows from the figures that, with
respect to the compounds R3AI and R2Al, the samarium-aluminium system
is a borderline case and the formation of R3AI may become very likely under
slightly altered purity conditions as we have proved experimentally now.
R3Al2
These compounds are only found for rare-earth elements for which the atomic
radii are smaller than that of samarium, viz. Gd3A12' Y3A12'Tb3Al2' DY3AI2'
H03Al2 and Er3A12' It has been shown that they are isotypic and possess the
Zr3Al2-type structure 2.12). An attempt to prepare the compounds Yb3Al2
and Eu3Al2 has not been successful.
RAl
In addition to the intermediate phases of this composition, presented in the .
figures, a monoaluminide is found for Tb, Ho and Dy. Although the stability
of such compounds seems not to be influenced by the decrease in metallic radius
on going from lanthanum to erbium, its crystal structure certainly is. As
reported previously 2), the compounds RAl have an orthorhombic lattice and
can be classified into two groups. For R = La and Ce the CeAI type 10) is
found, whereas for R = Pr, Nd, Srn, Gd, Tb, Ho and Er one observes the
ErAl18) type; Y behaves differently as it forms a CrB-type monoaluminide.
Due to difficulties in obtaining single crystals of these peritectically melting
compounds, there are no structural details for the CeAI type hor for the ErAI
type. It could be shown in the mean time that, by small changes in the experimental conditions, compounds belonging to the ErAl type can be transformed
into those of the CeAl type. If e.g. PrAl is homogenized in' an Al203 crucible
K. H. J. BUSCHOW and J. H. N. van VUCHT
for two weeks just above 700°C the ErAI type is obtained when cooled quickly
but a transformation
in structure from the ErAI type to the CeAI type takes
place when cooled rather slowly. The CeAl-type modification of GdAl has been
observed by Gschneidner 1~).If the lattice constants of the two modifications
are compared it may be seen that the orthorhombic unit cells of the CeAl type
and of the ErAI type are related in the following way:
(1) the' two unit cells have one axis in common (a-axis),
(2) the basal planes (perpendicular
to a) of the ErAI type are the oblongs
obtained from the diagonals of the CeAI basal planes and the distance
between two adjacent diagonals.
In table III the lattice constants calculated
TABLE
in this manner
from the lattice
III
lattice constants (A)
compound
CeAl type
(exp.)
ErAI type
(calc.)
ErAI type
(exp.)
PrAI
a
b
c
5·70
7·64
9·22
5·70
5·88
11·97
5·74
5·96
11'78
5.58 13)
GdAI
a
b
c
5·58
5·86
11·90
5·66
5·89
11·53
7·66
9·11
constants of the CeAI type are gathered in the second column. The agreement
with the experimental values for the ErAI type in the third column is striking .
. In addition to the two structure types mentioned, RAl compounds have been
reported to have the CsCI type of structure 5). Iandelli 16) and also Baenziger
and Moriarty 17) could not obtain this type in the single-phase form. Runnalls
and Lorimer 5), however, obtained the CsCI type for SmAl as single crystals
by means of a reaction between gaseous Sm and the Al203 crucible. We tried
in vain to obtain the CsCI structure type by applying raw materials of different
purity and different methods of preparation. In our experiments the RAl compounds were prepared via the liquid phase and annealed afterwards because of
the peritectical decomposition. In view ofthese results and its rathervoluminous
structüre we believe the CsCI type to be metastable relatively to the ErAI type.
The orthorhombic ErAl type has furthermore been observed for GdAI single
crystals by Stalinski 14) and for HoAI by Meyer 11). Kissell and Wallace 15)
observed the CeAI type for the first four rare-earth elements and a mixture of
SYSTEMATIC
ARRANGEMENT
OF THE BINARY RARE-EARTH-AI
SYSJ'!lMS
239
both orthorhombic structure types for the heavier rare-earth elements. Preliminary experiments indicate that it is not unlikely that the CeAI type can be
obtained from the ErAI type by applying a combination of high temperature
and high pressure. A somewhat similar transformation has been achieved 21)
for CrB-type YAl: a treatment of 6 h.at a pressure of 35 kb and a temperature
of 500 DCfollowed by quenching yielded a modification of the ErAl type with
the cell dimensions a = 5·61 A, b = 5·77 A and c = 11·47 A. If the element Y
is arranged between the rare-earth elements as suggested in sec. 1, then the
new structure obtained is exactly what one would expect. This again is a demonstration ofthe effect ofthe radius ratio on the stability of the structures formed
in these systems.
RAl2
As can be seen from the figures, these compounds have the highest melting
points in the phase diagrams. They all belong to the well-known cubic Lavesphase compounds 3). The occurrence of these compounds as line compounds
has been questioned by Gschneidner 6) on the grounds of a rather large spread
of the lattice constants reported in the literature. A more d~tailed X-ray investigation for the compounds LaAI2, CeAl2 and PrAl2 in the course of our
experiments did not, however, point to a homogeneity range of any significance.
These Laves-phase compounds are found for all rare-earth metals. It has been
demonstrated by McMasters and Gschneidner 19) that as the radius of the rare, earth metal becomes larger, a hexagonal structure of the AlB2 type may become
likely for compounds with the same electron-to-atom ratio. In the case of
lanthanum the structure type mentioned has indeed been observed 20), though
as a compound that deviates from the stoichiometrie composition viz.
!
Lao.ssA12.12·
In the compounds RAl2 ,Yb and Eu are divalent. As the metallic radii of
these elements then exceed that of La, attempts have been made to obtain
similar structures for the corresponding Eu and Yb compounds, but without
success.
RAl3
It has long been thought that the compounds RAl3 only exist for the smaller
rare-earth elements beyond samarium. That the phase mentioned has often been
overlooked may be due to the fact that in the case of La, Ce, Pr,·Nd and Srn
the compound RAl3 is decomposed peritectoidically at higher temperatures into
RAl2 and a phase we are inclined to name R3Alll' The relationship between the
rare-earth metallic radius and the crystal structure is most interesting for these
RAl3 compounds.
For large metallic radii the hexagonal Ni3Sn type is found (La, Ce, Pr, Nd, ,
240
K,' H. J. BUSCHOW
and J. 'R' N. 'Van VUCHT
-.
.,
_..
. _.'
•
Srn and Gd) while for small metallic radii the cubic CU3Au structure is observed
(Er 1B), Tm B.22),Yb and Sc 23)). For the elements in between (Y, Tb, Dy,
Ho) structures are observed that po.ssess rather large unit cells in which cubic
and hexagonal stacking are mixed in an ordered way.
As the radius of R decreases, the structure of the corresponding RAl3 compound shows relatively more cubic stacking: YAl3 and TbAl3 belong to the
BaPb3 type and have 331/3 % cubic character, DyAh and HoAl3 belong to
the HoAl3 type 24) and have 60 % cubic character. By increasing x continuously in the quasibinary compounds Gd1_xErxAl~ and Y1-xErxA13 both the
BaPb3 type and HoAl3 type were observed; in addition a third type was observed, viz. the Ni3 Ti type having 50 % cubic character. By these experiments it
has been possible to determine the limits for the metallic-radius ratio between
which the different structures of the rare-earth trialuminides are stable. One of
the surprising results of this investigation is that three different structure types
areformed for, ~ variation in radius .ratio rRIl'AI of only 2·5 %. It has ,been
suggested previously 24) that in making a choice from all the possible ordered
mixtures of hexagonal and cubic stacking. sequences"in this transition region
(see e.g. table III of ref. 24) kinetic advantages may play a role. It is true that
the repeat periods found experimentally for given percentages of hexagonal
stacking are virtually the smallest possible. This supposition of a kinetic advantage has only significanee if the growth of the crystals proceeds along the
e-axis making use of the Burgers vector (which remains the same whether a
given repeat period is stacked rhombohedrally or hexagonally). Experimentally
it was found that, in agreement with normal thermodynamic considerations,
two-phase regions exist between the different stackings in the pseudo-binary
mixtures of GdAI3-ErAI3 and YAI3-ErAI3' At present we have found some
new indications which make the kinetic arguments less probable: ErAl3' earlier
reported to be purely cubic (Cu3Au type), turned out to become rhombohedral
(HoAI3 type, 15 layer, hehee-stacked 24)) when vacuum-annealed during about
ten weeks at 500 °C; HoAl3, which in the as-cast and the annealed state contained only the rhombohedral IS-layer phase appeared to be partly of the
CU3Au type when splat-cooled. These results suggest that the different modifications exist as stable compounds at different temperatures. Similar experiments
on DyAl3 showed that here the IS-layer (Ho.Alj-type) structure is the hightemperature modification, After vacuum-annealing during 3.weeks at 800 °C
the 4-layer Ni3Ti type (he-stacked) was obtained as the main phase. The lattic~
constants for the phases of the compounds RAl3 observed in addition to those
reported in ref. 14 are
'
a - DyAl3 (Ni3Ti type): a = 6·082 A, e
f3 - HoAl3 (Cu3Au type): a '4'22 A;.
a - ErAl3 (HoAl3 type): a = 6·025 A, e
= 9·531 A;
= 35·675 A.
SYSTEMATIC
ARRANGEMENT
OF THE BINARY RARE-EARTH-Al
SYSTEMS
241
The Ni3 Ti type of structure for DyA13 and the Cu3Au type of structure for
HoA13 have also been observed by Baenziger and Hegenbarth 12) and by
Moriarty, Gordon and Humphreys 26). The discrepancy between their observations and those reported by us previously 24) may now also be understood
in terms of cooling rates during the preparation and annealing of the samples.
It is furthermore of interest to note that Yb, according to its crystal structure
and the corresponding cubic-lattice constant, has a metallic radius which lies
beyond that of Er and Tm. That means that as far as the compound YbAl3 is
concerned, Yb does not have the valence of 2 usually found in its alloys but the
valence 3. This is confirmed by measurements of the magnetic susceptibility;
YbA13 at room temperature has an effective moment of 4·6 [LB (the theoretical
value of g {J(J
IW/2 for Yb+++ is 4·50). In the case of Eu no compound
EuA13 has been observed.
+
R3A1U (RAI4)
Figure I shows that beyond 75 at. % aluminium only for the rare-earth elements
with a relatively large metallic radius an additional compound is formed. The
alkaline-earth elements Ca, Sr and Ba which have atomic radii larger than those
of the rare-earth metals are known to form intermetallic compounds with
aluminium of the tetragonal BaAl4 type. Europium, when in the divalent state,
has a radius which exceeds that of lanthanum whose value lies between that of
calcium and strontium. Since the valency of europium is the same as those of the
alkaline-earth metals the occurrence of a EuAl4 compound of the structure
mentioned should be very likely and has indeed been observed 25).
A long time we have thought that the compound richest in aluminium
observed for the first few lanthanide elements, could also be represented by the
formula RAl4 and that the high-temperature modification of these compounds
belong also to the BaAl4 type mentioned above 20). The low-temperature
modification of the compounds RA14 seemed to be related to the BaA14 type
in a simple manner: if the tetragonal unit cell of the latter type is represented
by a X a X c, then the unit cell of the compounds a- RAl4 can be described as
a X 3a X c which is orthorhombic instead of tetragonal. Recent investigations 27)
have shown, however, that the correct formula for the low-temperature modifications of the rare-earth compounds is R3A111instead of RA14' and that it is
very likely that the high-temperature modifications have the same composition.
If so, then the high-temperature modifications have the BaAl4 type of structure
in which at random one twelfth of the aluminium sites are vacant. This means
that the stability of these compounds is increased by an eatropy contribution
which becomes larger as the temperature rises. The a-B transition observed at
about 1000 °C for these compounds then results in an ordering ofthe mentioned
vacancies in a manner that the a-type unit cell becomes three times as large as
that of the (3-modification.
242
K. H. J. BUSCHOW and J. H. N. van VUCHT,
A rather curious. case is encountered in the samarium-aluminium system:
the phase ,8-Sm3Alll melts on cooling, forming a mixture of solid SmAl3 and
aluminium-rich liquid. The phase a-Sm3Alll was observed incidentally after
repeated temperature-cycling of a sample with 75 at. % AI. It has not been
possible to reproduce the experiment so that it is very likely that a-Sm3Alll is
a metastable compound, possibly stabilized in this particular case by some
unknown impurity. Another possibility is that, due to certain circumstances,
Sm3Alll has been cooled belowthe metastable transformation point without
decomposing. The lattice constants ofthe compounds a-R3Alll are summarized
in table IV.
TABLE IV
lattice constants (A)
compound
a-La3Alll
a-Ce3Alll
a-Pr3Alll
a-Nd3Alll
a-Sm3Alll
a
b
c
4·431
4·395
4·446
4·359
4·333
13·142
13·025
12·949
12·924
12·81
10·132
10·092
10·005
10·017
9·97
Solid solution Al(R)
There is no experimental evidence for a noticeable solid solubility of any
rare-earth metal in aluminium.
Eindhoven, December 1966
I
SYSTEMATIC
ARRANGEMENT
OF THE BINARY RARE-EARTH-AI
lanthanum-aluminium
243
SYSTEMS
cerium-aluminium
·e
ti
<ê
...J
I
'"
...J
ti
lS'
0
20
«ti
...J
<ê'" <ê'"
ti
...J
40
60
at.O,.AI
ti
...J
«
'"
ti
...J
I
t:I
80
<ê
100
0
praseodymium-aluminium
....
0-
*
0
«
",-
.... <C
0- '"
hl:
20
ll40
60
at."!. AI
40
60
at."!. AI
80
100
neodymium-aluminium
<ê
«....
0-
20
I
t:I
80
«
100
u
z
I
'IJ
0
U
z
20
'"
« «'" «'" u
Z
u
z
U
z
40
60
at.o,. AI
Fig. 1. Equilibrium diagrams between Al and rare-earth metals.
"C
Z
I
d
80
<ê
100
244
K. H. J. BUSCHOW and J. H. N. van VUCHT
qcdolinturn-oluminiurn
surncriurn-clurniniurn
·C
y
-
/1\
.
/
1
l'
\
":"-11\
"
1
I--
,
I
\ I
<I:
\:'
1---
O~'\,
-4"
\
I
I,
100
...
Vl
~E_I,
,c!:!,
', ..-
,,
,,
,
,
.
I
I
I
-
50 OlE
<
I
E
N
Vl
8
o
20
~
Vl
Vl Vl
40 60
at .,. Al
o,
<
80
o
<!)<!)
0
20
<
<I:
<
'0 '0
<!)<!)
'tl
~
100
~
« <
ff'O
'0
E E
E
Vl
s:
<I:
<
40
80
60
100
at."!. Al
yttrium-aluminium
erbium-aluminium
1)
>j
6
f.\\
]]!I
\
C
,
\
I
/
I
,
\
,,
/~
'. ",...,.t.....
\~r-
I
I
,
'
f-Î\
\
\
I
,
\
\
1000
-
-,
\
\
\
,,
\ \
,
,,
\
\
\
,
\
-
50 Ol-
<~ <:;:{... <... <...
UJ UJ
UJ UJUJ
N
...
UJ
M
<
...
0
20
40
60
80
J~
'ï
~
100
o
<I~
>->20
~.!.
<I: <I:
>- >-
<
>-
40
60
at."!. Al
ot."/. Al
Fig. 1 (continued).
<
80
100
SYSTEMATIC
ARRANGEMENT
OF THE BINARY RARE-EARTH-AI
SYSTEMS
245
REFERENCES
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)
14)
15)
16)
17)
18)
19)
20)
21)
22)
23)
24)
25)
26)
27)
C. E. Lundin and D. T. Klodt, Trans. ASM 54, 168, 1961.
K. H. J. Buschow, J. less-common Met. 8, 209, 1965.
J. H. Wernick and S. GeIler, Trans. AIME 218, 866, 1960.
A. landeIli, Symposium on physical chemistry of metallic solutions and intermetallic
compounds (Natl. Phys. Lab., Teddington 1958), H. M. Stationery Office, London, 1959.
O. J. C. RunnaIls and G. W. Lorimer, J. less-common Met. 8, 75, 1965.
K. A. Gschneidner
Jr, Rare earth alloys, D. van Nostrand Company, 1961.
K. H. J. Buschow and J. H. N. van Vucht, Philips Res. Repts 20, 15-22, 1965.
K. H. J. Buschow and J. F. Fast, Z. phys, Chem. N.F. 50, 1-10, 1966.
H. J. Williams, J. H. Wernick, E. A. Nesbitt and R. C. Sherwood, J. phys, Soc.
Japan 17 suppl. B-1, 91-95, 1962.
J. H. N. van Vuch t, Z. MetalIk. 48, 253, 1957.
A. Meyer, J. less-common Met. 10, 121-129, 1965.
N. C. Baenziger and J. J. Hegenbarth,
Acta cryst. 17, 620, 1960.
K. A. Gschneidner,
Acta cryst. 18, 1082-1083, 1965.
B. Stalinski
and S. Pokrzywnicki,
Phys, Stat. sol. 14, KI57-KI60, 1966.
F. Kissel and W. E. WaIlace, J. less-common Met. 11, 417-422,1966.
A. landeIli, Atti Congr. intern. Chim. Roma 1933.
N. C. Baenziger and J. L. Moriarty, Acta cryst. 14, 948-950, 1961.
K. H. J. Buschow and J. H. N. van Vucht, Z. Metallk.-56, 9-13, 1965.
O. D. MeMasters and K. A. Gschneidner
Jr, Nuclear Metallurgy SeriesX, 93,1964.
K. H. J. Buschow, Philips Res. Repts 20, 337-348, 1965.
C. J. M. Rooymans, K. H. J. Buschow and J. H. N. van Vucht, to be published.
T. 1. Jones, L. R. Norlock and R. R. Boucher, J. less-common Met. 5,128, 1963.
V. N. Rechkin, L. K. Lamikhov and T. 1. Samsonova, Soviet Phys. Cryst. 9, 325,
1964.
J. H. N. van Vucht and K. H. J. Buschow, J. less-common Met. 10, 98-107, 1965.
J. H. N. van Vucht and K. H. J. Buschow, Philips Res. Repts 19, 319, 1964.
J. L. Moriarty, R. O. Gordon and J. E. Humphreys,
Acta cryst. 19, 285, 1965.
A. H. Gomes de Mesquita and K. H. J. Buschow, Acta cryst. 22, 497, 1967.