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Crystal structure of RCu5−xPbx (R=Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases
Journal of Alloys and Compounds 314 (2001) 206–208
L
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Crystal structure of RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases L.D. Gulay* ´ Str. 2, P.O. Box 1410, 50 -950 Wrocł aw, W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okolna Poland Received 25 July 2000; accepted 28 September 2000
Abstract The crystal structures of the RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases have been determined using X-ray powder ¯ m, Pearson code cF24 ). diffraction method. The investigated compounds crystallize with AuBe 5 structure type (space group F43 2001 Elsevier Science B.V. All rights reserved. Keywords: Rare earth compounds; Crystal structure; X-ray diffraction
1. Introduction
2. Experimental
The compounds with the RCuPb (R5La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Yb) composition which crystallize with CaIn 2 structure type (space group P63 /mmc) have been studied previously [1,2]. Other R–Cu–Pb compounds have not been studied till now. The absence in literature of any information about the existence of the phases with the RCu 52x Pb x composition (R is a rare earth metal) which ¯ m) crystallize with AuBe 5 structure type (space group F43 induced to study the possibility of the formation of such phases. The RCu 5 compounds have been found in the R–Cu systems [3,4]. According to [4] RCu 5 (R5La, Ce, Pr, Nd, Sm, Eu and Yb) compounds crystallize with CaCu 5 structure type (space group P6 /mmm), RCu 5 (R5Ho, Er, Tm and Lu) compounds crystallize with AuBe 5 structure ¯ m), whereas RCu 5 (R5Gd, Tb, Dy type (space group F43 and Ho) compounds crystallize with AuBe 5 structure type (low temperature) and CaCu 5 structure type (high temperature). The YCu 5 compound does not exist [4]. The results of the crystal structure determination of the RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm and Lu) phases are given in the present paper.
The samples with total mass of about 1 g were prepared by arc melting of pure metals (the purity of the ingredients was better than 99.9 wt%) in high-purity argon atmosphere. All alloys were remelted two times to ensure homogeneity. The mass losses after the melting were less than 1 wt%. After the melting samples were sealed in evacuated quartz ampoules and annealed at 870 K (670 K for samples with La, Ce, Pr, Nd, Sm) during 720 h. After annealing the ampoules were quenched in cold water. X-ray powder diffraction patterns of the samples were recorded using DRON-2.0 powder diffractometer (Fe Ka radiation, 208#2Q#1008, Si as internal standard). A phase analysis was carried out and boundaries of the solid solutions were determined. The diffraction data for crystal structure determination of the samples with Gd, Ho, Er, Tm and Lu were collected using a HZG-4a (Cu Ka radiation, 208#2Q#1308, step scan mode with a step size of 0.058 and counting time of 15 s per data point). For the samples with Y, Tb and Dy we used a Siemens D5000 powder diffractometer (Cu Ka radiation, 108#2Q#1208, step scan mode with a step size of 0.028 and counting time of 19 s per data point). Lattice parameters were calculated using least-squares method. Crystal structure determination was performed using DBWS-9411 program [5].
*On leave from the Inorganic Chemistry Department, L’viv National University, L’viv, Ukraine. E-mail address: [email protected] (L.D. Gulay).
0925-8388 / 01 / $ – see front matter 2001 Elsevier Science B.V. All rights reserved. PII: S0925-8388( 00 )01256-1
L.D. Gulay / Journal of Alloys and Compounds 314 (2001) 206 – 208
207
3. Results and discussion The RCu 5 (R5La, Ce, Pr, Nd, Sm and Gd) compounds with CaCu 5 structure and RCu 5 (R5Tb, Dy, Ho, Er, Tm and Lu) compounds with AuBe 5 structure were identified during the phase analysis of the samples. The non-existence of YCu 5 compound was confirmed. The GdCu 5 compound with AuBe 5 structure type was not identified at investigated temperature. The samples with Eu and Yb were not studied. The lattice parameters of the RCu 5 (R5Tb, Dy, Ho, Er, Tm and Lu) compounds were not determined, because X-ray patterns of the respective samples were not good quality for reliable lattice parameters calculation. The lattice parameters for these compounds were taken from Refs. [6,7]. The compounds with the YCu 52x Pb x (x50.26–0.89) and GdCu 4.60 Pb 0.40 compositions were found during the phase analysis of the samples in the R–Cu–Pb (R5Y, Gd) systems at 870 K. The crystal structures were determined using X-ray powder diffraction method. X-ray powder diffraction patterns were indexed assuming a cubic unit cell with the lattice parameters listed in Table 1. The composition of the samples, intensities of reflections and lattice parameters proved that these compounds are iso¯ m) structural with AuBe 5 structure type (space group F43 [8]. The results of the crystal structure determination of the YCu 52x Pb x (x50.26–0.89) and GdCu 4.60 Pb 0.40 compounds are listed in Table 1. RCu 5 based solid solutions were found during the phase analysis of the samples of the R–Cu–Pb (R5Tb, Dy, Ho, Er, Tm, Lu) systems at 870 K. The boundary compositions and corresponding lattice parameters are given in Table 1. The solid solutions are isostructural with AuBe 5 structure type. The results of the crystal structure calculation of the
Fig. 1. Projection of the crystal structure of YCu 52x Pb x (x50.26–0.89) compound on the XY plane and coordination polyhedra of Y (a), M1 (b) and M2 (c) atoms.
samples which occupy the boundary compositions are given in Table 1. The RCu 52x Pbx (R5La, Ce, Pr, Nd, Sm) phases with AuBe 5 structure were not found. The projection of the crystal structure of the YCu 52x Pb x (x50.26–0.89) compound on the XY plane and the coordination polyhedra of the Y (a), M1 (mixture of randomly distributed Cu and Pb atoms) (b), and M2 (mixture of randomly distributed Cu and Pb atoms) (c) atoms are presented in Fig. 1. The Y and M2 atoms form 16-vertices (c.n.516), M1 atom — octahedrons (c.n.512).
Table 1 Results of the crystal structure determination of the RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases Compound (RCu 52x Pbx )
YCu 4.7424.11 Pb 0.2620.89 GdCu 4.60 Pb 0.40 TbCu 524.44 Pb 020.56 DyCu 524.47 Pb 020.53 HoCu 524.50 Pb 020.50 ErCu 524.34 Pb 020.66 TmCu 524.55 Pb 020.45 LuCu 524.42 Pb 020.58 a
Fixed.
a ˚ (A)
7.0993(2) 7.1448(2) 7.1288(5) 7.041 [6] 7.1555(2) 7.027 [6] 7.1452(2) 7.016 [6] 7.0965(2) 7.003 [6] 7.1129(4) 6.991 [6] 7.0930(4) 6.970 [7] 7.1140(1)
Pb (at%)
4.3 14.9 6.6 0 9.3 0 8.8 0 8.3 0 11.0 0 7.5 0 9.6
x
0.26 0.89 0.40 0 0.56 0 0.53 0 0.50 0 0.66 0 0.45 0 0.58
R 4(a) 000 2 Beq. (A˚ )
M1 16(e) xxx (x50.625)a
M2 4(c)
R P , PwP
˚ 2) Beq. (A
Occupancy
˚ 2) Beq. (A
Occupancy
1.00(5) 1.06(5) 0.83(7)
1.55(7) 1.30(6) 1.21(9)
1.27(6) 1.05(7) 1.07(8)
0.68(6)
1.64(9)
0.75(5)
1.65(8)
0.69(8)
1.11(9)
0.67(7)
1.32(9)
0.81(6)
1.42(8)
0.78(4)
1.25(7)
16Cu 14.71(7)Cu11.29(7)Pb 15.60(9)Cu10.40(9)Pb 16Cu 15.57(3)Cu10.43(3)Pb 16Cu 15.35(7)Cu10.65(7)Pb 16Cu 15.49(8)Cu10.51(8)Pb 16Cu 15.17(7)Cu10.83(7)Pb 16Cu 15.63(8)Cu10.37(8)Pb 16Cu 15.73(6)Cu10.27(6)Pb
2.98(2)Cu11.02(2)Pb 1.74(6)Cu12.26(6)Pb 2.81(8)Cu11.19(8)Pb 4Cu 2.21(3)Cu11.79(3)Pb 4Cu 2.54(7)Cu11.46(7)Pb 4Cu 2.51(7)Cu11.49(7)Pb 4Cu 2.17(7)Cu11.83(7)Pb 4Cu 2.56(8)Cu11.44(8)Pb 4Cu 1.97(6)Cu12.03(7)Pb
1 1 1 ] ] ] 4 4 4
1.15(8) 0.91(6) 0.92(9) 0.93(8) 1.13(7) 0.92(5)
0.0239, 0.0320 0.0222, 0.0293 0.0219, 0.0276 0.0242, 0.0319 0.0280, 0.0379 0.0363, 0.0502 0.0397, 0.0564 0.0319, 0.0535 0.0332, 0.0439
L.D. Gulay / Journal of Alloys and Compounds 314 (2001) 206 – 208
208
Table 2 ˚ and coordination numbers (c.n.) of the atoms Interatomic distances (d, A) for the YCu 52x Pb x (x50.26–0.89) compound Atoms
Y
–12M1 –4M2 M1 –6M1 –3Y –3M2 M2 –12M1 –4Y
˚ d (A)
c.n.
x50.26
x50.89
2.9432(7) 3.0741(2) 2.501(1) 2.9432(7) 2.9432(7) 2.9432(7) 3.0741(2)
2.9621(7) 3.0938(2) 2.526(1) 2.9621(7) 2.9621(7) 2.9621(7) 3.0938(2)
16
The extent of the homogeneity ranges of the RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases are given in Fig. 2. The increase of the lattice parameter with the increase of the Pb and decrease of the Cu contents for all investigated RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases agree with the atomic radii of the Cu and Pb atoms.
12 16
˚ The interatomic distances (d, A), and coordination numbers of the atoms for the YCu 52x Pb x (x50.26–0.89) compound are listed in Table 2. All interatomic distances are in good agreement with the sum of the respective atomic radii.
Acknowledgements The author is grateful to Professor Dr K. Łukaszewicz for many valuable discussions and the Sniadecki Brothers Foundation for the financial support of his research project in W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences.
References
Fig. 2. Homogeneity ranges of the RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases.
[1] D. Mazzone, D. Rossi, R. Marazza, R. Ferro, J. Less-Common Metals 84 (1982) 301. [2] P. Salamakha, O. Zaplatynsky, J. Alloys Comp. 260 (1997) 127. [3] P. Villars, L.D. Calvert (Eds.), Pearson’s Handbook of Crystallographic Data for Intermetallic Phases, Vol. 1-3, American Society for Metals, Metal Park, OH, 1985, p. 3258. [4] T.B. Massalsky (Ed.), Binary Alloy Phase Diagrams, Vols. 1–3, American Society for Metals, Metal Park, OH, 1986, p. 1850. [5] R.A. Young, A. Sakthivel, T.S. Moss, C.O. Paria-Santos (Eds.), Program DBWS-9411 for Rietveld analysis of the X-ray and neutron powder diffraction patterns, Georgia Institute of Technology, Atlanta, GA, 1995. [6] K.H.J. Buschow, A.S. van der Goot, J. Birkhan, J. Less-Common Metals 19 (1969) 433. [7] A. Iandelli, A. Palenzona, J. Less-Common Metals 25 (1971) 333. [8] N.C. Baenziger, R.E. Rundle, A.I. Snow, A.S. Wilson, Acta Crystallogr. 3 (1950) 34.
L
www.elsevier.com / locate / jallcom
Crystal structure of RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases L.D. Gulay* ´ Str. 2, P.O. Box 1410, 50 -950 Wrocł aw, W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okolna Poland Received 25 July 2000; accepted 28 September 2000
Abstract The crystal structures of the RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases have been determined using X-ray powder ¯ m, Pearson code cF24 ). diffraction method. The investigated compounds crystallize with AuBe 5 structure type (space group F43 2001 Elsevier Science B.V. All rights reserved. Keywords: Rare earth compounds; Crystal structure; X-ray diffraction
1. Introduction
2. Experimental
The compounds with the RCuPb (R5La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Yb) composition which crystallize with CaIn 2 structure type (space group P63 /mmc) have been studied previously [1,2]. Other R–Cu–Pb compounds have not been studied till now. The absence in literature of any information about the existence of the phases with the RCu 52x Pb x composition (R is a rare earth metal) which ¯ m) crystallize with AuBe 5 structure type (space group F43 induced to study the possibility of the formation of such phases. The RCu 5 compounds have been found in the R–Cu systems [3,4]. According to [4] RCu 5 (R5La, Ce, Pr, Nd, Sm, Eu and Yb) compounds crystallize with CaCu 5 structure type (space group P6 /mmm), RCu 5 (R5Ho, Er, Tm and Lu) compounds crystallize with AuBe 5 structure ¯ m), whereas RCu 5 (R5Gd, Tb, Dy type (space group F43 and Ho) compounds crystallize with AuBe 5 structure type (low temperature) and CaCu 5 structure type (high temperature). The YCu 5 compound does not exist [4]. The results of the crystal structure determination of the RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm and Lu) phases are given in the present paper.
The samples with total mass of about 1 g were prepared by arc melting of pure metals (the purity of the ingredients was better than 99.9 wt%) in high-purity argon atmosphere. All alloys were remelted two times to ensure homogeneity. The mass losses after the melting were less than 1 wt%. After the melting samples were sealed in evacuated quartz ampoules and annealed at 870 K (670 K for samples with La, Ce, Pr, Nd, Sm) during 720 h. After annealing the ampoules were quenched in cold water. X-ray powder diffraction patterns of the samples were recorded using DRON-2.0 powder diffractometer (Fe Ka radiation, 208#2Q#1008, Si as internal standard). A phase analysis was carried out and boundaries of the solid solutions were determined. The diffraction data for crystal structure determination of the samples with Gd, Ho, Er, Tm and Lu were collected using a HZG-4a (Cu Ka radiation, 208#2Q#1308, step scan mode with a step size of 0.058 and counting time of 15 s per data point). For the samples with Y, Tb and Dy we used a Siemens D5000 powder diffractometer (Cu Ka radiation, 108#2Q#1208, step scan mode with a step size of 0.028 and counting time of 19 s per data point). Lattice parameters were calculated using least-squares method. Crystal structure determination was performed using DBWS-9411 program [5].
*On leave from the Inorganic Chemistry Department, L’viv National University, L’viv, Ukraine. E-mail address: [email protected] (L.D. Gulay).
0925-8388 / 01 / $ – see front matter 2001 Elsevier Science B.V. All rights reserved. PII: S0925-8388( 00 )01256-1
L.D. Gulay / Journal of Alloys and Compounds 314 (2001) 206 – 208
207
3. Results and discussion The RCu 5 (R5La, Ce, Pr, Nd, Sm and Gd) compounds with CaCu 5 structure and RCu 5 (R5Tb, Dy, Ho, Er, Tm and Lu) compounds with AuBe 5 structure were identified during the phase analysis of the samples. The non-existence of YCu 5 compound was confirmed. The GdCu 5 compound with AuBe 5 structure type was not identified at investigated temperature. The samples with Eu and Yb were not studied. The lattice parameters of the RCu 5 (R5Tb, Dy, Ho, Er, Tm and Lu) compounds were not determined, because X-ray patterns of the respective samples were not good quality for reliable lattice parameters calculation. The lattice parameters for these compounds were taken from Refs. [6,7]. The compounds with the YCu 52x Pb x (x50.26–0.89) and GdCu 4.60 Pb 0.40 compositions were found during the phase analysis of the samples in the R–Cu–Pb (R5Y, Gd) systems at 870 K. The crystal structures were determined using X-ray powder diffraction method. X-ray powder diffraction patterns were indexed assuming a cubic unit cell with the lattice parameters listed in Table 1. The composition of the samples, intensities of reflections and lattice parameters proved that these compounds are iso¯ m) structural with AuBe 5 structure type (space group F43 [8]. The results of the crystal structure determination of the YCu 52x Pb x (x50.26–0.89) and GdCu 4.60 Pb 0.40 compounds are listed in Table 1. RCu 5 based solid solutions were found during the phase analysis of the samples of the R–Cu–Pb (R5Tb, Dy, Ho, Er, Tm, Lu) systems at 870 K. The boundary compositions and corresponding lattice parameters are given in Table 1. The solid solutions are isostructural with AuBe 5 structure type. The results of the crystal structure calculation of the
Fig. 1. Projection of the crystal structure of YCu 52x Pb x (x50.26–0.89) compound on the XY plane and coordination polyhedra of Y (a), M1 (b) and M2 (c) atoms.
samples which occupy the boundary compositions are given in Table 1. The RCu 52x Pbx (R5La, Ce, Pr, Nd, Sm) phases with AuBe 5 structure were not found. The projection of the crystal structure of the YCu 52x Pb x (x50.26–0.89) compound on the XY plane and the coordination polyhedra of the Y (a), M1 (mixture of randomly distributed Cu and Pb atoms) (b), and M2 (mixture of randomly distributed Cu and Pb atoms) (c) atoms are presented in Fig. 1. The Y and M2 atoms form 16-vertices (c.n.516), M1 atom — octahedrons (c.n.512).
Table 1 Results of the crystal structure determination of the RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases Compound (RCu 52x Pbx )
YCu 4.7424.11 Pb 0.2620.89 GdCu 4.60 Pb 0.40 TbCu 524.44 Pb 020.56 DyCu 524.47 Pb 020.53 HoCu 524.50 Pb 020.50 ErCu 524.34 Pb 020.66 TmCu 524.55 Pb 020.45 LuCu 524.42 Pb 020.58 a
Fixed.
a ˚ (A)
7.0993(2) 7.1448(2) 7.1288(5) 7.041 [6] 7.1555(2) 7.027 [6] 7.1452(2) 7.016 [6] 7.0965(2) 7.003 [6] 7.1129(4) 6.991 [6] 7.0930(4) 6.970 [7] 7.1140(1)
Pb (at%)
4.3 14.9 6.6 0 9.3 0 8.8 0 8.3 0 11.0 0 7.5 0 9.6
x
0.26 0.89 0.40 0 0.56 0 0.53 0 0.50 0 0.66 0 0.45 0 0.58
R 4(a) 000 2 Beq. (A˚ )
M1 16(e) xxx (x50.625)a
M2 4(c)
R P , PwP
˚ 2) Beq. (A
Occupancy
˚ 2) Beq. (A
Occupancy
1.00(5) 1.06(5) 0.83(7)
1.55(7) 1.30(6) 1.21(9)
1.27(6) 1.05(7) 1.07(8)
0.68(6)
1.64(9)
0.75(5)
1.65(8)
0.69(8)
1.11(9)
0.67(7)
1.32(9)
0.81(6)
1.42(8)
0.78(4)
1.25(7)
16Cu 14.71(7)Cu11.29(7)Pb 15.60(9)Cu10.40(9)Pb 16Cu 15.57(3)Cu10.43(3)Pb 16Cu 15.35(7)Cu10.65(7)Pb 16Cu 15.49(8)Cu10.51(8)Pb 16Cu 15.17(7)Cu10.83(7)Pb 16Cu 15.63(8)Cu10.37(8)Pb 16Cu 15.73(6)Cu10.27(6)Pb
2.98(2)Cu11.02(2)Pb 1.74(6)Cu12.26(6)Pb 2.81(8)Cu11.19(8)Pb 4Cu 2.21(3)Cu11.79(3)Pb 4Cu 2.54(7)Cu11.46(7)Pb 4Cu 2.51(7)Cu11.49(7)Pb 4Cu 2.17(7)Cu11.83(7)Pb 4Cu 2.56(8)Cu11.44(8)Pb 4Cu 1.97(6)Cu12.03(7)Pb
1 1 1 ] ] ] 4 4 4
1.15(8) 0.91(6) 0.92(9) 0.93(8) 1.13(7) 0.92(5)
0.0239, 0.0320 0.0222, 0.0293 0.0219, 0.0276 0.0242, 0.0319 0.0280, 0.0379 0.0363, 0.0502 0.0397, 0.0564 0.0319, 0.0535 0.0332, 0.0439
L.D. Gulay / Journal of Alloys and Compounds 314 (2001) 206 – 208
208
Table 2 ˚ and coordination numbers (c.n.) of the atoms Interatomic distances (d, A) for the YCu 52x Pb x (x50.26–0.89) compound Atoms
Y
–12M1 –4M2 M1 –6M1 –3Y –3M2 M2 –12M1 –4Y
˚ d (A)
c.n.
x50.26
x50.89
2.9432(7) 3.0741(2) 2.501(1) 2.9432(7) 2.9432(7) 2.9432(7) 3.0741(2)
2.9621(7) 3.0938(2) 2.526(1) 2.9621(7) 2.9621(7) 2.9621(7) 3.0938(2)
16
The extent of the homogeneity ranges of the RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases are given in Fig. 2. The increase of the lattice parameter with the increase of the Pb and decrease of the Cu contents for all investigated RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases agree with the atomic radii of the Cu and Pb atoms.
12 16
˚ The interatomic distances (d, A), and coordination numbers of the atoms for the YCu 52x Pb x (x50.26–0.89) compound are listed in Table 2. All interatomic distances are in good agreement with the sum of the respective atomic radii.
Acknowledgements The author is grateful to Professor Dr K. Łukaszewicz for many valuable discussions and the Sniadecki Brothers Foundation for the financial support of his research project in W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences.
References
Fig. 2. Homogeneity ranges of the RCu 52x Pb x (R5Y, Gd, Tb, Dy, Ho, Er, Tm, Lu) phases.
[1] D. Mazzone, D. Rossi, R. Marazza, R. Ferro, J. Less-Common Metals 84 (1982) 301. [2] P. Salamakha, O. Zaplatynsky, J. Alloys Comp. 260 (1997) 127. [3] P. Villars, L.D. Calvert (Eds.), Pearson’s Handbook of Crystallographic Data for Intermetallic Phases, Vol. 1-3, American Society for Metals, Metal Park, OH, 1985, p. 3258. [4] T.B. Massalsky (Ed.), Binary Alloy Phase Diagrams, Vols. 1–3, American Society for Metals, Metal Park, OH, 1986, p. 1850. [5] R.A. Young, A. Sakthivel, T.S. Moss, C.O. Paria-Santos (Eds.), Program DBWS-9411 for Rietveld analysis of the X-ray and neutron powder diffraction patterns, Georgia Institute of Technology, Atlanta, GA, 1995. [6] K.H.J. Buschow, A.S. van der Goot, J. Birkhan, J. Less-Common Metals 19 (1969) 433. [7] A. Iandelli, A. Palenzona, J. Less-Common Metals 25 (1971) 333. [8] N.C. Baenziger, R.E. Rundle, A.I. Snow, A.S. Wilson, Acta Crystallogr. 3 (1950) 34.