Intermetallics 7 (1999) 931±935
The system Ce±Ag±Sn: phase equilibria and magnetic properties P. Boulet a,b,c, D. Mazzone b, H. NoeÈl a,*, P. Riani b, P. Rogl c, R. Ferro b a
Laboratoire de Chimie du Solide et Inorganique MoleÂculaire. U.M.R. C.N.R.S 6511, Universite de Rennes 1, Avenue du GeÂneÂral Leclerc, 35042 Rennes, France b Dipartimento di Chimica e Chimica Industrial, UniversitaÁ di Genova Via Dodecaneso 31, 16146 Genova, Italy c Institut fuÈr Physikalische Chemie der UniversitaÈt Wien, A-1090 Wien, WaÈhringerstra e 42, Austria Received 3 December 1998; accepted 10 December 1998
Abstract Phase relations in the ternary system Ce±Ag±Sn have been established for an isothermal section at 750 C. Experimental techniques used were optical microscopy, EPMA and X-ray powder analysis of arc-melted samples which had been annealed at 750 C for 10 days and quenched to room temperature. Phases equilibria are characterized by the formation of three ternary compounds: CeAgSn (CaIn2-type), Ce5AgSn3 (Hf5CuSn3-type), and Ce3Ag4Sn4 (Gd3Cu4Ge4-type). CeAg2Sn2, earlier reported to form and crystallize in the CaBe2Ge2-type, was not observed in the present study. All these ternary phases order magnetically at low temperature; our measurements reveal that Ce5AgSn3 is ferromagnetic below TC=5 K, and Ce3Ag4Sn4 is antiferromagnetic below TN=9 K. # 1999 Elsevier Science Ltd. All rights reserved. Keywords: A. Intermetallics, miscellaneous; B. Phase diagram; B. Magnetic properties
1. Introduction
2. Experimental
Intensive studies have been devoted to the physics of strong electron correlations in metallic systems involving 5f or 4f electron metals, in relation to their interesting properties ranging from magnetic ordering to superconductivity, with heavy-fermion ground states. It is known that the low-temperature properties of intermetallic compounds are in many cases very sensitive to heat treatments, suggesting some structural disorder and the existence of homogeneity domains. For a proper understanding of these in¯uences, a detailed knowledge of the phase relations is a prerequisite. Thus, the aim of the present paper is to provide basic information on compound formation, crystal chemistry and the intrinsic magnetic properties of the ternary compounds in the complete isothermal section of the ternary system Ce±Ag±Sn at 750 C. As a contribution to this topic, we recently reported on the crystal chemistry and magnetic properties of the ternary system U±Ag±Sn [1].
The polycrystalline ingots were obtained by arc-melting stoichiometric amounts of the constituent elements under an atmosphere of high purity argon on a watercooled copper hearth, using a Ti±Zr alloy as an oxygen/ nitrogen getter. The materials were used in the form of ingots as supplied by Strem Chemicals (cerium 3N, tin 2N8) and by Merck AG (silver 5N). In order to ensure homogeneity, the arc-melted buttons were turned over and remelted 3 times, with a total weight loss lower than 0.5%. The buttons were wrapped in tantalum foils, sealed in evacuated quartz tubes, annealed at 750 C for 10 days and quenched by submerging in water. Precise lattice parameters and standard deviations were obtained by least squares re®nement of room-temperature INEL CPS 120 powder diractometer data, using silicon as internal standard. Optical and scanning electron microscopy were employed for metallographic examination, and electron-probe microanalysis (EPMA) of the phases was performed using an energy-dispersive analyzer. The pure constituent metals were used as standards for quantitative determinations. Magnetic measurements of an annealed polycrystalline sample were carried out in a superconducting quantum interference device (SQUID) magnetometer in
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0966-9795/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0966 -9 795(98)00144 -7
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P. Boulet et al. / Intermetallics 7 (1999) 931±935
the temperature range 5±300 K and in magnetic ®elds up to 3 T.
Table 1 Crystallographic data for the unary and binary boundary phases in the system Ce±Ag±Sn Compound
3. Results and discussion 3.1. The isothermal section of the Ce±Ag±Sn system at 750 C
The isothermal section at 750 C of the Ce±Ag±Sn ternary system is illustrated in Fig. 1. The basic data concerning the binary boundary systems were essentially taken from the published phase diagrams [2], except for the system Ce±Sn, which was reinvestigated recently [3±5]. Table 1 summarizes the crystallographic data of the unary and binary phases [6]. Crystallographic data of solid phases in the ternary system evaluated by re®nements of the X-ray powder patterns, and EPMA results, are listed in Table 2. All the Ce±Sn binary compounds were con®rmed, with Ag-solubility ranging from 1% for Ce3Sn up to 10% for CeSn3. In agreement with the binary phase diagram [2], Ce5Sn3 was observed in the low-temperature modi®cation (tetragonal W5Si3 type). In the Ce±Ag system we con®rm the existence of CeAg, CeAg2 and Ce14Ag51, but EPMA results indicated a phase with composition closer to Ce2Ag9 than to the CeAg4 previously reported. In agreement with reference [2], Ce14Ag51 was found to exhibit a small
Pearson Space symbol Group
Structure type
Unit cell dimension in AÊ a
Ag Sn Sn Ce
Ce Ce Ce Ag3Sn Ag4Sn CeAg CeAg
CeAg2 CeAg2 CeAg2 Ce14Ag51 Ce2Ag9 Ce3Sn Ce5Sn3 Ce5Sn3 Ce5Sn4 Ce11Sn10 Ce3Sn5 Ce3Sn7 Ce2Sn5 CeSn3
cF4 cF8 tI4 cI2 cF4 hP4 cF4 oP8 hP2 cP2 tP2 ??? ??? oI12 hP68 ??? cP4 tI32 hP16 oP36 tI84 oC32 oC20 oC28 cP4
Fm3m Fd3m I41/amd Im3m Fm3m
Cu Cdia Sn W Cu P63/mmc La Fm3m Cu Pmmn TiCu3 P63/mmc Mg Pm3m CsCl P4/mmm HgMn
b
c
4.086 6.489 5.831 4.12 5.161 3.681 11.857 5.155 5.968 4.780 2.965 3.785 3.739
5.184 4.782 3.811
Imma P6/m
CeCu2 Gd14Ag51
4.800 12.88
Pm3m I4/mcm P63/mcm Pnma I4/mmm Cmcm Cmmm Cmmm Pm3m
AuCu3 W5Si3 Mn5Si3 Sm5Ge4 Ho11Ge10 Pu3Pd5 Ce3Sn7 Ce2Sn5 AuCu3
4.935 12.60 6.170 9.335 6.810 8.337 16.05 8.480 11.97 17.82 10.25 8.225 10.58 4.524 25.74 4.610 4.559 35.01 4.619 4.722
Fig. 1. Isothermal section at 750 C of the Ce±Ag±Sn system.
7.090
3.181
8.205 9.455
P. Boulet et al. / Intermetallics 7 (1999) 931±935
933
Table 2 Crystallographic and EPMA data of some Ce±Ag±Sn alloys quenched from 750 C Alloy nominal composition (at%)
Phases identi®ed
Space group
Ce(Agx Sn1ÿx)3 Sn Ce(Agx Sn1ÿx)3 Sn Ag3Sn Ce(Agx Sn1ÿx)3 Ce3Ag4Sn4 Ag3Sn Ce(Agx Sn1ÿx)3 Ce3Ag4Sn4 Ce3Sn7 Ce(Agx Sn1ÿx)3 Ce3Sn7 Ce(Agx Sn1ÿx)3 Ce2Sn5 Ce3Ag4Sn4 Ce3Sn7 Ce3Sn5 Ce3Sn5 Ce3Ag4Sn4 CeAgSn Ce3Sn5 Ce11Sn10 CeAgSn Ce5Sn4 Ce11Sn10 CeAgSn Ce5Sn4 Ce5Sn3 CeAgSn Ce5AgSn3 Ce5Sn3 CeAgSn Ce5AgSn3 Ce5Sn3 CeAg1ÿxSnx Ce5AgSn3 Ce14Ag51 CeAgSn Ce5AgSn3 CeAg1ÿxSnx CeAg2ÿxSnx Ce5AgSn3 Ce14Ag51 CeAg2ÿxSnx Ag Ce14Ag51 CeAgSn Ag Ce3Ag4Sn4 CeAgSn Ag Ce3Ag4Sn4 Ag3Sn Sn Ag3Sn Ce3Ag4Sn4 Ce(AgxSn1ÿx)3
Pm3m I41/amd Pm3m I41/amd Pmmm Pm3m
Pearson Symbol
Structure type
Unit cell dimension in AÊ a
Ce20Ag5Sn75 Ce15Ag33Sn52 Ce25Ag15Sn60 Ce25Ag10Sn65 Ce27Ag5Sn68 Ce25Ag5Sn70 Ce35Ag10Sn55 Ce30Ag30Sn40 Ce37Ag13Sn50 Ce45Ag10Sn45 Ce50Ag10Sn40 Ce55Ag9Sn36 Ce56Ag22Sn22 Ce33Ag44Sn23 Ce50Ag25Sn25 Ce40Ag45Sn15 Ce15Ag80Sn5 Ce25Ag50Sn25 Ce10Ag70Sn20 Ce20Ag40Sn40
Immm Pmmm Pm3m Immm Cmmm Pm3m Cmmm Pm3m
Cmmm Immm Cmmm Cmcm Cmcm Immm P63/mmc Cmcm I4/mmm P63/mmc Pnma I4/mmm P63/mmc Pnma !4/mcm P63/mmc P63/mcm I4/mcm P63/mmc P63/mcm I4/mcm Pm3m
P63/mcm P6/m P63/mmc P63/mcm Pm3m ? P63/mcm P6/m ? Fm3m P6/m P63/mmc Fm3m Immm P63/mmc Fm3m Immm Pmmn I41/amd Pmmn Immm Pm3m
cP4 tI4 cP4 tI4 oP8 cP4 oI22 oP8 cP4 oI22 oC20 cP4 oC20 cP4 oC28 oI22 oC20 oC32 oC32 oI22 hP6 oC32 tI84 hP6 oP36 tI84 hP6 oP36 tI32 hP6 hP18 tI32 hP6 hP18 tI32 cP2 hP18 hP68 hP6 hP18 cP2
AuCu3 Sn AuCu3 Sn TiCu3 AuCu3 Gd3Cu4Ge4 TiCu3 AuCu3 Gd3Cu4Ge4 Ce3Sn7 AuCu3 Ce3Sn7 AuCu3 Ce2Sn5 Gd3Cu4Ge4 Ce3Sn7 Pu3Pd5 Pu3Pd5 Gd3Cu4Ge4 CaIn2 Pu3Pd5 Ho11Ge10 CaIn2 Sm5Ge4 Ho11Ge10 CaIn2 Sm5Ge4 W5Si3 CaIn2 Ti5Ga4 W5Si3 CaIn2 Ti5Ga4 W5Si3 CsCl Ti5Ga4 Gd14Ag51 CaIn2 Ti5Ga4 CsCl
4.6970(2) 5.839(2) 4.686(1) 5.833(2) 5.8885(2) 4.688(1) 15.532(9) 5.948(1) 4.6958(2) 15.547(8) 4.529(2) 4.7042(6) 4.528(1) 4.7040(5) 4.568(2) 15.550(2) 4.527(1) 10.221(3) 10.217(4) 15.537(4) 4.786(2) 10.263(3) 11.885(5) 4.781(1) 8.316(2) 11.895(5) 4.777(1) 8.316(5) 12.563(3) 4.776(1) 9.574(3) 12.572(8) 4.785(2) 9.593(3) 12.563(6) 3.764(1) 9.572(3) 12.887(2) 4.785(2) 9.569(4) 3.769(2)
hP18 hP68
Ti5Ga4 Gd14Ag51
9.574(3) 12.891(3)
cF4 hP68 hP6 cF4 oI22 hP6 cF4 oI22 oP8 tI4 oP8 oI22 cP4
Cu Gd14Ag51 CaIn2 Cu Gd3Cu4Ge4 CaIn2 Cu Gd3Cu4Ge4 TiCu3 Sn TiCu3 Gd3Cu4Ge4 AuCu3
4.086(2) 12.90(1) 4.762(3) 4.088(2) 15.544(2) 4.780(1) 4.088(1) 15.542(4) 5.887(2) 5.831(2) 5.905(1) 15.538(6) 4.685(5)
EPMA results (at%) b
c 3.181(2)
4.745(5)
3.180(1) 5.167(3)
7.359(5) 4.785(2)
4.679(2) 5.178(9)
7.362(3) 25.798(7)
4.679(1) 4.629(1)
25.791(6)
4.631(2)
35.08(7) 7.378(1) 25.801(5) 8.180(5) 8.182(8) 7.365(1)
4.631(5) 4.690(1) 4.629(1) 10.46(2) 10.451(4) 4.685(1) 7.764(9) 10.598(7) 17.791(7) 7.752(3) 8.497(8) 17.802(6) 7.741(2) 8.497(3) 6.159(1) 7.742(2) 6.734(3) 6.161(4) 7.749(8) 6.749(5) 6.155(5)
8.213(3) 16.045(5) 16.045(5)
6.728(3) 9.479(8) 7.749(8) 6.741(4) 6.735(3) 9.482(5) 9.517(8) 7.736(6) 7.371(1)
4.682(1) 7.725(1)
7.372(1) 4.757(1)
4.680(1) 5.166(3) 3.182(2) 5.177(1) 4.688(1)
4.765(3) 7.372(1)
Ce
Ag
Sn
26.0 0.0 0.2 26.1 28.3 0.3 26.7 28.5 31.9 26.7 31.2 26.6 28.2 26.8 31.0 39.0
9.5 1.5 73.2 8.9 34.1 76.1 8.6 34.2 0.5 5.6 0.5 4.9 0.1 36.5 2.0 2.8
64.5 98.5 26.6 65.0 37.6 23.6 64.7 37.3 67.6 67.8 68.3 68.5 71.6 36.7 67.0 58.2
52.1 49.9 34.8
3.1 44.8 4.9 45.2 30.2 35.0
55.0 64.2 52.3 54.9 24.2 34.7 54.9 52.1 35.9 52.1 24.0 36.7 0.3 21.5 33.8 0.4
9.3 1.0 40.5 11.1 75.4 32.3 11.2 39.0 57.2 10.5 75.3 56.8 99.7 73.5 32.7 98.4
34.8 0.0 28.4 0.0
32.2 33.0 98.0 2.0 34.5 37.1 75.8 24.2
0.0 28.7 26.1
73.7 26.3 34.6 36.7 9.6 64.3
35.7 34.8 7.2 34.0 0.4 33.0 33.9 8.9 6.9 37.4 0.7 6.4 0.0 5.0 33.5 1.2
continued
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P. Boulet et al. / Intermetallics 7 (1999) 931±935
Table 2Ðcontd Alloy nominal composition (at%)
Phases identi®ed
Space group
Pearson Symbol
Structure type
Unit cell dimension in AÊ a
Ce18Ag80Sn2 Ce20Ag78Sn2 Ce22Ag76Sn2 Ce56Ag33Sn11 Ce19Ag81 Ce21Ag79
Ag Ce14Ag51 Ce2Ag9ÿxSnx Ag Ce14Ag51 Ce2Ag9ÿxSnx Ce14Ag51 Ce5Sn3 CeAg1ÿxSnx Ce3Sn Ag Ce2Ag9 Ce14Ag51 Ce2Ag93
Fm3m P6/m ? Fm3m
cF4 hP68
Cu Gd14Ag51
P6/m
cF4 hP68
Cu Gd14Ag51
P6/m I4/mcm Pm3m Pm3m Fm3mc
hP68 tI32 cP2 cP4 F4
Gd14Ag51 W5Si3 CsCl AuCu3 Cu
hP68
Gd14Ag51
? P6/m ?
homogeneity domain Ce/Ag, and a solubility of 5 at% of tin was observed in this phase. The other two binary compounds, CeAg2 and CeAg, admit larger solubilities of 7 and 8 at% of tin, respectively. In the latter case, re®nement of the X-ray powder diraction data corresponding to the cubic (CsCl type) unit cell revealed a small decrease of the lattice parameter from 3.78 AÊ for the binary compound to 3.76 AÊ for the end of the solid solution. The existence of the CeAg2 phase was deduced from dierential thermal analysis experiments [7] but no crystallographic data are available. During this work, a phase with this composition was also observed by EPMA but no crystal structure determination could be successfully performed because of its high rate of corrosion. For the tin-rich part of the system, the liquidus curve was drawn as a dashed line, as it could not be determined precisely in our experimental procedure. Samples in this region showed primary crystallization of bSn and/or Ag3Sn. The Ce-rich liquidus corner was also drawn with similar approximation. Three ternary compounds are formed at 750 C: CeAgSn, Ce3Ag4Sn4 and Ce5AgSn3 (see Table 3). A phase with composition CeAg2Sn2, was earlier reported [8] to form and crystallize with the primitive CaBe2Ge2 structure type, but in the present study samples of this composition appeared to be a three-phase mixture at 750 C: Ce3Ag4Sn4 ÿCeSn3ÿxAgx-liquid ( Sn-Ag3Sn). In fact, the ternary phase with the atomic ratio 1/2/2 was not observed at all, even after long annealing times at temperatures lower and higher than 750 C. Thus we conclude that such a phase does not form. The ternary phase CeAgSn crystallizes with the hexagonal CaIn2 type [9]. According to the analyses of some samples around this composition, a slight homogeneity region CeAg1ÿxSn1+x, corresponding to a substitution of Ag by Sn with x75 K), the inverse magnetic susceptibility versus temperature follows the Curie±Weiss law: C=
T ÿ leading to eff 2:52 B =Ce with ÿ23 K, revealing trivalent cerium in this ternary. As mentioned above, we found no evidence for the formation of any compound with the CaBe2Ge2 type of structure in the Ce±Ag±Sn system and according to the present study, all samples prepared with this initial composition 1/2/2 contain Sn (Table 2). Thus, the superconducting transition at TS=3.5 K reported previously [8] for the composition CeAg2Sn2 is probably due to the presence of small amounts of tin in the
investigated samples, and should not be considered as an intrinsic property of any ternary compound in the Ce±Ag±Sn ternary system. Acknowledgements This research was performed as part of an EEC-Human Capital and Mobility Network ERBCHRX-CT93-0284. P.R. and H.N. wish to thank the CNRS-Austrian Academy of Sciences for support under grant PICS-134. References [1] Boulet P, Vybornov M, Simopoulos A, Kostikas A, NoeÈl H, Rogl P. J Alloys Compds 1999;283:41. [2] Massalski TB. Binary alloy phase diagrams, 2nd ed. Materials Park, OH: ASM, 1990. [3] Franceschi EA, Costa GA. J Therm Analysis 1988;34:451. [4] Franceschi EA. J Less Common Met 1979;66:175. [5] Boucherle J-X, Givord F, Lejay P, Schweizer J, Stunault A. Acta Cryst 1988;B44:377. [6] Villars P, Calvert LD. Pearson's handbook of crystallographic data for intermetallic phases, 2nd ed. Materials Park, OH: ASM International, 1991. [7] Stapf I, Jehn H. J Less Common Met 1984;98:173. [8] GoÈrlich EA. acta Polonica 1994;A85:253. [9] Mazzone D, Rossi D, Marazza R, Ferro R. J Less Common Met 1981;80:47. [10] Rieger W, Parthe E. Monatsh chemie 1968;99:291. [11] Salamakha PS, Zaplatyndky OV, Sologub OL, Bodak OI. Polish J Chem 1996;70:158. [12] Boulet P. PhD thesis, University of Rennes, 1997. [13] Lenkewitz M, Corsepius S, Stewart GR. J Alloys Compds 1996;241:121. [14] Sakurai J, Nakatani S, Adam A, Fujiwara H. J Magn Magn Mater 1992;108:143. [15] Boulet P, Potel M, Levet JC, NoeÈl H. J Alloys Compds 1997;262/ 263:22916. [16] Boulet P, NoeÈl H. Solid State Comm 1998;107(3):135. [17] Weitzer F, Hiebl K, Rogl P. J Less Common Met 1991;175:331.
