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The europium-palladium system
Jouwal of rhe trss-Commot~ Metals, 38 ( 1974) l--7 ‘? Elsevier Sequoia S.A., Lausanne Printed in The Netherlands
THE EUROPIUM-PALLADIUM
A. IANDELLI Istituto
SYSTEM
and A. PALENZONA
di Chimira
(Received
1
March
,fiska,
Uuiuersifd
di Geneva, Gcrtocl(Itdy)
2, 1974)
SUMMARY
The binary system europium-palladium has been investigated by differential thermal analysis, X-ray diffraction, metallography and magnetic susceptibility measurements. Six intermetallic phases have been found. Four of these, ciz., Eu5Pd2? Eu,Pd,, EuPd, and EuPd,, contain divalent europium; in the remaining two, EuPd, and EuPd,, the europium behaves as a trivalent rare-earth metal. To allow comparison with EuPd, the structures of CaPd, SrPd and BaPd have been determined.
INTRODUCTION
In many binary alloys and intermetallic compounds ytterbium behaves, by contrast with the neighbouring rare-earth metals, as a divalent element. But in the systems Yb-Cu’, Yb-Au2, Yb-Pd3, and Yb-Ni4 Yb shows a tendency to become trivalent as the composition of the alloy is changed by increasing the percentage of the second element. Each of these systems appears to be divided into two ranges of composition, the first corresponding to analogous alloys of the alkaline-earth metals (divalent Yb) and the second, which has higher concentrations of the second metal, to those of the other rare-earth metal systems (trivalent Yb). Similar behaviour could be expected to occur in the europium alloys, the differences being due to the higher stability of the divalent state of europium, as compared with that of ytterbium. We have studied the Eu-Pd system in order to compare the behaviour of Eu with that of Yb; in particular, to establish the range of compositions for the existence of Eu(II1) and Yb(II1) compounds. Studies of the lattice spacings, magnetic susceptibilities and Mijssbauer spectra for this system have already been carried out by Harris and Longworth5.6 Their results will be compared with those obtained in the present work. EXPERIMENTAL
The Eu-Pd phase diagram has been determined by means of differential thermal analysis, micrographic and X-ray methods, and measurements of the magnetic susceptibility.
2
A. IANDELLI, A. PALENZONA
The europium used was purchased from the Koch-Light Laboratories, England, and had a claimed purity of 99.5%. Palladium was obtained from JohnsonMatthey, England, with a purity of 99.9%. Owing to the high vapour pressure of Eu metal, the Eu-Pd alloys were prepared in the same way as the alloys of Yb, and thermally analysed in molybdenum containers into which mixtures of Eu turnings, prepared under very pure argon, and of Pd powder, were pressed. The molybdenum containers were then closed with molybdenum caps by arc welding under argon. Unfortunately, in the case of alloys containing more than 75 at.% Pd, the MO reacts with the Pd and dissolves in the alloy, giving incorrect thermal effects. Such alloys were prepared in alumina crucibles, soldered under argon into Fe or MO containers, melted and annealed at different temperatures, and examined micrographically and by X-rays. Some were thermally analysed, after the abovementioned preparation, by transferring into MO containers and carrying out the DTA analysis by heating only.
1400-
1200-
600
ia
EU
Fig.
1. The europium-palladium
Pd
phase diagram.
THE EUROPIUM-PALLADIUM
SYSTEM
3
RESULTS
The temperature-composition phase diagram is shown in Fig. 1. Starting from pure Eu (m.p. 820°C; reported valuer2, 822”C), the melting point of the alloys falls to 545°C corresponding to a eutectic mixture at 17.5 at.% Pd. The m.p. then rises to the melting temperature (810°C) of the compound Eu,Pd2 (40 at.% Pd). Between 17.5 and 40 at.% Pd another compound is formed, which decomposes at 610°C and corresponds to the formula Eu5Pd2. The compositions of these two compounds are in agreement with the X-ray results. We have made an extensive examination of alloys between the eutectic composition and Eu3Pd2 since, in the YbbPd system previously examined, another compound with the composition Yb3Pd exists, but no indication of the presence of a similar compound in the Eu-Pd system was found. Beyond Eu,Pd,, two phases, EuPd and EuPd,, are formed, which decompose at 855 and 1330°C respectively, and a maximum melting point of 1425°C is reached for the compound EuPd,. As already observed, the Pd-rich alloys are difficult to investigate, due to their reactivity with the MO containers and also on account of the difficulty in the establishment of the equilibrium structure. A compound EuPd, exists between 75 and 90 at.% Pd; this decomposes at a temperature (1105C) which is a little above the melting point of the eutectic (lOSOC), and has a composition near to that of the eutectic. The compound may be easily observed micrographically, as may be seen in the micrograph (Fig. 2) which appears to be almost identical with that already reported for the Sm-Pd 84.9 at.% Pd alloy’. The compound crystallizes in the form of lamellae, which can be separated from the bulk alloy, but which, when examined by X-rays, appear to consist of multiple twinned crystals, simulating a hexagonal symmetry. As it has been impossible to obtain single crystals of this phase its composition was evaluated micrographically. The most probable formula lies very close to EuPd,.
Fig. 2. Eu/Pd 85 at.% Pd. ( x 100).
4
A. IANDELLI,
Fig. 3. Eu/Pd
A. PALENZONA
87.5 at.% Pd. ( x 100)
A eutectic, containing 87.5 at.% Pd, m.p. 108o”C, exists between EuPd, and a final solid solution of Eu in Pd. The micrograph of an alloy with this composition is shown in Fig. 3 and also appears similar to the photograph of the corresponding alloy in the Sm-Pd system ‘. The extension of the ‘solid solution of Eu in Pd was not thermally explored, as it has already been determined by Harris and Longworth5. TABLE
I
CRYSTALLOGRAPHIC Comp.
DATA FOR THE EUROPIUMPPALLADIUM
’ struct.
we* Eu
c12-Im3m
EuSPd2
WI mC28-C2/c
Eu,Pd* EuPd
(Mn&) hR45 oC8-Cmcm
Lattice
constants
a
Notes
(A)
b
4.581 4.580 17.299 /?=97”15’ 9.204 4.097
PHASES References
c this work 12 this work
7.919
6.985
17.384 11.121
4.447
11.075
4.450
this work this work
(CrB) EuPd,
cF24-Fd3m
4.092 7.763
(WW EuPd,
cP4-Pm3m (Au%)
Pd
cF4-Fm3m (Cu)
* The symbols
of the space groups
-
7.761 4.101 4.101 4.088 4.095 4.081 4.078 3.892 3.891 are preceded
6 this work
Eu-rich Eu-rich stoichiom. stoichiom. Pd-rich Pd-rich
by the Pearson
notation’a.
5 this work c this work 5 this work 5 this work 13
THE ~URO~IUM-PALLADIUM
5
SYSTEM
The crystal structure results for the six compounds existing in the Eu-Pd system, are given in Table I. Eu,Pd,, Eu3Pdz. and EuPd were examined with X-rays on single crystals by Weissenberg and precession photographs. Eu,Pd, crystallizes in the Mn,C,-type and appears to be isomorphous with YbsPdZ3. The crystal structure of Eu,Pd, has not yet been determined; it is rhombohedral and, from the measured density (7.75 g’cm3), 27 Eu and 18 Pd atoms are contained in the unit cell. EuPd crystallizes with the CrB-type. in agreement with the results of Longworth and Harris6. EuPd, has a structure of the MgCuz-type, and. as already known5 its lattice constant appears to be almost identical in the neighbouring compositions. On the contrary. EuPd, with an AuCu,-type structure, exists over a small range of solid solubility. Magnetic susceptibility measurements have been made on the several phases and have shown that Eu behaves as a divalent element in the first four compounds, and as a trivalent R.E. metal in EuPd, and EuPd,. These results are in agreement with the preceding work of Harris and Longworth”. DISCUSSION
Table II contains data on the compounds existing in the Eu-Pd and Yb-Pd systems, and permits some conclusions to be drawn. TABLE
II
EXISTENT Compound
PHASES V*
IN THE Eu-Pd
AND Yb-Pd
Peritectic
struct.
or melfiny
we
SYSTEMS Compound
-
. . ..- __... V
_
Puritectic
struct.
or meltiny
type
temperature
te~l~er~it~lre
wi
i’“Cl
EuSPdz Eu,Pd, EuPd
2 2 2
p. 610
Mn&G
m. 810 p. 855
rhomb CrB
EuPd,
2
p. 1330
MgCu,
EuPd, EuPd,
3 3
m. 1425 p. 1105
AUCU, unkn.
Yb,Pd Yb,Pdz
2 2
p. 670 p. 695
YbPd Y&Pd,
3 3 3 3 3 3
tn. 1460 nl. 1415 Ill. 1360 p. 1382
YbPd,,,, YbPd, YbPdz.1, YbPd,
p. 1i85 m. 1700
Fe& MnsC2 _ CSCI Pu3Pd4 unkn. unkn. unkn. AuCu,
* V = valency of Eu or Yb.
In the alloys with Pd, Eu may form compounds with valency 3 for higher Pd percentages than in the case of Yb, which is consistent with the higher stability of Eu”. Only the compounds Eu,Pdz and YbsPd,, containing divalent Eu and Yb, are isomorphous, as are also EuPd, and YbPd, containing Eur” and Ydi’, respectively. The greatest part of the phase diagram appears therefore to vary according to the different valencies of the two eiements, and also to the differences between the atomic radii of EL?’ and Yb”, and of Eu”’ and Yb”‘, respectively. The
6
A. IANDELLI,
A. PALENZONA
last factor is probably responsible for the existence of Yb,Pd and EuPd, and the nonexistence of the corresponding Eu,Pd and YbPds. Concerning the last-named composition, within the R.E./Pd systems which have been examined, it is only in the Sm-Pd alloys that such a phase, SmPd,, exists; this is similar to EuPd,. The phase diagram confirms the results obtained by Harris and Longworth5T6, concerning the phases EuPd, EuPd,, EuPd, and EuPd,. On the Eu-rich side, the existence of Eu,Pd and EuzPd phases can be excluded and these should be replaced by Eu,Pd, and Eu,Pd,. In the first part of the system, Eu behaves as a divalent element and should be compared with the alkaline-earth metals (M). We have prepared the corresponding MPd compounds, and have determined their crystal structures with the results given in Table III, together with that of EuPd. CaPd has been studied recently by Mendelson and Tanaka’, who found the same structure type, with a=3.515 A. TABLE III CRYSTALLOGRAPHIC Compound
Str. We
CSCI CrB CrB CrB
CaPd EuPd SrPd BaPd
DATA FOR MPd PHASES Lattice constants (A)
.._~
a
b
C
3.522 4.097 4.19 4.35
11.121 11.31 11.79
4.447 4.52 4.68
From CaPd to SrPd the structure type changes and EuPd appears to be isomorphous with SrPd, in agreement with its atomic dimensions. Another series of simple compounds of the alkaline-earth metals is represented by the MPdz phases: these are already known and crystallize with the MgCu,-type structure. The lattice constants again show, together with those of EuPd,, a regular increase in the sequence Ca-Eu-Sr-Ba. SrPd, and CaPd,, in contrast with EuPd,, may give solid solutions with Pd. The reported values of the lattice constants of SrPd, range from 7.800 A to 7.826 Ag*lo, and for CaPd, we have found values ranging from 7.660 A (7.665 A, according to”) to 7.609 A for compositions which are richer in Pd. A comparison with the alkaline-earth metals is no longer possible beyond the composition EuPd,. None of the compounds CaPd,, SrPd, and BaPd, is known to exist, and the same holds for CaPds. The compound SrPd5 is knowng**o, but this has a structure (of CaCu,-type) which is different from that of EuPd,. REFERENCES 1 2 3 4
A. A. A. A.
Iandelli and A. Iandelli and A. Iandelli and A. Palenzona and
Palenzona, J. Less-Common Metals,25 (1971) 333. Palenzona, .J. Less-Common Metals, 18 (1969) 221. Palenzona, Reo. Chim. Minirale, 10 (1973) 303. S. Cirafici, J. Less-Common Metals, 33 (1973) 361.
THE EUROPIUM-PALLADIUM
7
SYSTEM
5 I. R. Harris and G. Longworth, J. Less-Common Met&, 23 (1971) 281. 6 G. Longworth and I. R. Harris, J. ~ess-Co~~~ Met&, 33 (1973) 83. 7 0. Loebich and E. Raub, J. ~ess-Cu~~on Me&, 30 (1973) 47. 8 M. H. Mendelsohn and J. Tanaka, J. Less-Common Metals, 32 (1973) 314. 9 T. Heumann and M. Kniepmeyer, Z. Anorg. Al/g. Chem.. 290 (1957) 191. 10 E. A. Wood and W. B. Compton, Acta Cryst., 11(1958) 429. 11 N. Harmsen and T. Heumann, Monatsh. Chem., 102 (1971) 1442. 12 K. A. Gschneidner, U.S. At. Energy Comm. Rept. no IS-1757, 1968, p. 84. 13 W. 3. Pearson, A Handbook of Lattice Spacings and Strucrures of Metals Pereamon Press, Oxford, 1967.
and
Alloys.
Vol.
2,
THE EUROPIUM-PALLADIUM
A. IANDELLI Istituto
SYSTEM
and A. PALENZONA
di Chimira
(Received
1
March
,fiska,
Uuiuersifd
di Geneva, Gcrtocl(Itdy)
2, 1974)
SUMMARY
The binary system europium-palladium has been investigated by differential thermal analysis, X-ray diffraction, metallography and magnetic susceptibility measurements. Six intermetallic phases have been found. Four of these, ciz., Eu5Pd2? Eu,Pd,, EuPd, and EuPd,, contain divalent europium; in the remaining two, EuPd, and EuPd,, the europium behaves as a trivalent rare-earth metal. To allow comparison with EuPd, the structures of CaPd, SrPd and BaPd have been determined.
INTRODUCTION
In many binary alloys and intermetallic compounds ytterbium behaves, by contrast with the neighbouring rare-earth metals, as a divalent element. But in the systems Yb-Cu’, Yb-Au2, Yb-Pd3, and Yb-Ni4 Yb shows a tendency to become trivalent as the composition of the alloy is changed by increasing the percentage of the second element. Each of these systems appears to be divided into two ranges of composition, the first corresponding to analogous alloys of the alkaline-earth metals (divalent Yb) and the second, which has higher concentrations of the second metal, to those of the other rare-earth metal systems (trivalent Yb). Similar behaviour could be expected to occur in the europium alloys, the differences being due to the higher stability of the divalent state of europium, as compared with that of ytterbium. We have studied the Eu-Pd system in order to compare the behaviour of Eu with that of Yb; in particular, to establish the range of compositions for the existence of Eu(II1) and Yb(II1) compounds. Studies of the lattice spacings, magnetic susceptibilities and Mijssbauer spectra for this system have already been carried out by Harris and Longworth5.6 Their results will be compared with those obtained in the present work. EXPERIMENTAL
The Eu-Pd phase diagram has been determined by means of differential thermal analysis, micrographic and X-ray methods, and measurements of the magnetic susceptibility.
2
A. IANDELLI, A. PALENZONA
The europium used was purchased from the Koch-Light Laboratories, England, and had a claimed purity of 99.5%. Palladium was obtained from JohnsonMatthey, England, with a purity of 99.9%. Owing to the high vapour pressure of Eu metal, the Eu-Pd alloys were prepared in the same way as the alloys of Yb, and thermally analysed in molybdenum containers into which mixtures of Eu turnings, prepared under very pure argon, and of Pd powder, were pressed. The molybdenum containers were then closed with molybdenum caps by arc welding under argon. Unfortunately, in the case of alloys containing more than 75 at.% Pd, the MO reacts with the Pd and dissolves in the alloy, giving incorrect thermal effects. Such alloys were prepared in alumina crucibles, soldered under argon into Fe or MO containers, melted and annealed at different temperatures, and examined micrographically and by X-rays. Some were thermally analysed, after the abovementioned preparation, by transferring into MO containers and carrying out the DTA analysis by heating only.
1400-
1200-
600
ia
EU
Fig.
1. The europium-palladium
Pd
phase diagram.
THE EUROPIUM-PALLADIUM
SYSTEM
3
RESULTS
The temperature-composition phase diagram is shown in Fig. 1. Starting from pure Eu (m.p. 820°C; reported valuer2, 822”C), the melting point of the alloys falls to 545°C corresponding to a eutectic mixture at 17.5 at.% Pd. The m.p. then rises to the melting temperature (810°C) of the compound Eu,Pd2 (40 at.% Pd). Between 17.5 and 40 at.% Pd another compound is formed, which decomposes at 610°C and corresponds to the formula Eu5Pd2. The compositions of these two compounds are in agreement with the X-ray results. We have made an extensive examination of alloys between the eutectic composition and Eu3Pd2 since, in the YbbPd system previously examined, another compound with the composition Yb3Pd exists, but no indication of the presence of a similar compound in the Eu-Pd system was found. Beyond Eu,Pd,, two phases, EuPd and EuPd,, are formed, which decompose at 855 and 1330°C respectively, and a maximum melting point of 1425°C is reached for the compound EuPd,. As already observed, the Pd-rich alloys are difficult to investigate, due to their reactivity with the MO containers and also on account of the difficulty in the establishment of the equilibrium structure. A compound EuPd, exists between 75 and 90 at.% Pd; this decomposes at a temperature (1105C) which is a little above the melting point of the eutectic (lOSOC), and has a composition near to that of the eutectic. The compound may be easily observed micrographically, as may be seen in the micrograph (Fig. 2) which appears to be almost identical with that already reported for the Sm-Pd 84.9 at.% Pd alloy’. The compound crystallizes in the form of lamellae, which can be separated from the bulk alloy, but which, when examined by X-rays, appear to consist of multiple twinned crystals, simulating a hexagonal symmetry. As it has been impossible to obtain single crystals of this phase its composition was evaluated micrographically. The most probable formula lies very close to EuPd,.
Fig. 2. Eu/Pd 85 at.% Pd. ( x 100).
4
A. IANDELLI,
Fig. 3. Eu/Pd
A. PALENZONA
87.5 at.% Pd. ( x 100)
A eutectic, containing 87.5 at.% Pd, m.p. 108o”C, exists between EuPd, and a final solid solution of Eu in Pd. The micrograph of an alloy with this composition is shown in Fig. 3 and also appears similar to the photograph of the corresponding alloy in the Sm-Pd system ‘. The extension of the ‘solid solution of Eu in Pd was not thermally explored, as it has already been determined by Harris and Longworth5. TABLE
I
CRYSTALLOGRAPHIC Comp.
DATA FOR THE EUROPIUMPPALLADIUM
’ struct.
we* Eu
c12-Im3m
EuSPd2
WI mC28-C2/c
Eu,Pd* EuPd
(Mn&) hR45 oC8-Cmcm
Lattice
constants
a
Notes
(A)
b
4.581 4.580 17.299 /?=97”15’ 9.204 4.097
PHASES References
c this work 12 this work
7.919
6.985
17.384 11.121
4.447
11.075
4.450
this work this work
(CrB) EuPd,
cF24-Fd3m
4.092 7.763
(WW EuPd,
cP4-Pm3m (Au%)
Pd
cF4-Fm3m (Cu)
* The symbols
of the space groups
-
7.761 4.101 4.101 4.088 4.095 4.081 4.078 3.892 3.891 are preceded
6 this work
Eu-rich Eu-rich stoichiom. stoichiom. Pd-rich Pd-rich
by the Pearson
notation’a.
5 this work c this work 5 this work 5 this work 13
THE ~URO~IUM-PALLADIUM
5
SYSTEM
The crystal structure results for the six compounds existing in the Eu-Pd system, are given in Table I. Eu,Pd,, Eu3Pdz. and EuPd were examined with X-rays on single crystals by Weissenberg and precession photographs. Eu,Pd, crystallizes in the Mn,C,-type and appears to be isomorphous with YbsPdZ3. The crystal structure of Eu,Pd, has not yet been determined; it is rhombohedral and, from the measured density (7.75 g’cm3), 27 Eu and 18 Pd atoms are contained in the unit cell. EuPd crystallizes with the CrB-type. in agreement with the results of Longworth and Harris6. EuPd, has a structure of the MgCuz-type, and. as already known5 its lattice constant appears to be almost identical in the neighbouring compositions. On the contrary. EuPd, with an AuCu,-type structure, exists over a small range of solid solubility. Magnetic susceptibility measurements have been made on the several phases and have shown that Eu behaves as a divalent element in the first four compounds, and as a trivalent R.E. metal in EuPd, and EuPd,. These results are in agreement with the preceding work of Harris and Longworth”. DISCUSSION
Table II contains data on the compounds existing in the Eu-Pd and Yb-Pd systems, and permits some conclusions to be drawn. TABLE
II
EXISTENT Compound
PHASES V*
IN THE Eu-Pd
AND Yb-Pd
Peritectic
struct.
or melfiny
we
SYSTEMS Compound
-
. . ..- __... V
_
Puritectic
struct.
or meltiny
type
temperature
te~l~er~it~lre
wi
i’“Cl
EuSPdz Eu,Pd, EuPd
2 2 2
p. 610
Mn&G
m. 810 p. 855
rhomb CrB
EuPd,
2
p. 1330
MgCu,
EuPd, EuPd,
3 3
m. 1425 p. 1105
AUCU, unkn.
Yb,Pd Yb,Pdz
2 2
p. 670 p. 695
YbPd Y&Pd,
3 3 3 3 3 3
tn. 1460 nl. 1415 Ill. 1360 p. 1382
YbPd,,,, YbPd, YbPdz.1, YbPd,
p. 1i85 m. 1700
Fe& MnsC2 _ CSCI Pu3Pd4 unkn. unkn. unkn. AuCu,
* V = valency of Eu or Yb.
In the alloys with Pd, Eu may form compounds with valency 3 for higher Pd percentages than in the case of Yb, which is consistent with the higher stability of Eu”. Only the compounds Eu,Pdz and YbsPd,, containing divalent Eu and Yb, are isomorphous, as are also EuPd, and YbPd, containing Eur” and Ydi’, respectively. The greatest part of the phase diagram appears therefore to vary according to the different valencies of the two eiements, and also to the differences between the atomic radii of EL?’ and Yb”, and of Eu”’ and Yb”‘, respectively. The
6
A. IANDELLI,
A. PALENZONA
last factor is probably responsible for the existence of Yb,Pd and EuPd, and the nonexistence of the corresponding Eu,Pd and YbPds. Concerning the last-named composition, within the R.E./Pd systems which have been examined, it is only in the Sm-Pd alloys that such a phase, SmPd,, exists; this is similar to EuPd,. The phase diagram confirms the results obtained by Harris and Longworth5T6, concerning the phases EuPd, EuPd,, EuPd, and EuPd,. On the Eu-rich side, the existence of Eu,Pd and EuzPd phases can be excluded and these should be replaced by Eu,Pd, and Eu,Pd,. In the first part of the system, Eu behaves as a divalent element and should be compared with the alkaline-earth metals (M). We have prepared the corresponding MPd compounds, and have determined their crystal structures with the results given in Table III, together with that of EuPd. CaPd has been studied recently by Mendelson and Tanaka’, who found the same structure type, with a=3.515 A. TABLE III CRYSTALLOGRAPHIC Compound
Str. We
CSCI CrB CrB CrB
CaPd EuPd SrPd BaPd
DATA FOR MPd PHASES Lattice constants (A)
.._~
a
b
C
3.522 4.097 4.19 4.35
11.121 11.31 11.79
4.447 4.52 4.68
From CaPd to SrPd the structure type changes and EuPd appears to be isomorphous with SrPd, in agreement with its atomic dimensions. Another series of simple compounds of the alkaline-earth metals is represented by the MPdz phases: these are already known and crystallize with the MgCu,-type structure. The lattice constants again show, together with those of EuPd,, a regular increase in the sequence Ca-Eu-Sr-Ba. SrPd, and CaPd,, in contrast with EuPd,, may give solid solutions with Pd. The reported values of the lattice constants of SrPd, range from 7.800 A to 7.826 Ag*lo, and for CaPd, we have found values ranging from 7.660 A (7.665 A, according to”) to 7.609 A for compositions which are richer in Pd. A comparison with the alkaline-earth metals is no longer possible beyond the composition EuPd,. None of the compounds CaPd,, SrPd, and BaPd, is known to exist, and the same holds for CaPds. The compound SrPd5 is knowng**o, but this has a structure (of CaCu,-type) which is different from that of EuPd,. REFERENCES 1 2 3 4
A. A. A. A.
Iandelli and A. Iandelli and A. Iandelli and A. Palenzona and
Palenzona, J. Less-Common Metals,25 (1971) 333. Palenzona, .J. Less-Common Metals, 18 (1969) 221. Palenzona, Reo. Chim. Minirale, 10 (1973) 303. S. Cirafici, J. Less-Common Metals, 33 (1973) 361.
THE EUROPIUM-PALLADIUM
7
SYSTEM
5 I. R. Harris and G. Longworth, J. Less-Common Met&, 23 (1971) 281. 6 G. Longworth and I. R. Harris, J. ~ess-Co~~~ Met&, 33 (1973) 83. 7 0. Loebich and E. Raub, J. ~ess-Cu~~on Me&, 30 (1973) 47. 8 M. H. Mendelsohn and J. Tanaka, J. Less-Common Metals, 32 (1973) 314. 9 T. Heumann and M. Kniepmeyer, Z. Anorg. Al/g. Chem.. 290 (1957) 191. 10 E. A. Wood and W. B. Compton, Acta Cryst., 11(1958) 429. 11 N. Harmsen and T. Heumann, Monatsh. Chem., 102 (1971) 1442. 12 K. A. Gschneidner, U.S. At. Energy Comm. Rept. no IS-1757, 1968, p. 84. 13 W. 3. Pearson, A Handbook of Lattice Spacings and Strucrures of Metals Pereamon Press, Oxford, 1967.
and
Alloys.
Vol.
2,