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The Y2S3–La2S3–GeS2 system at 770 K
Journal of Alloys and Compounds 698 (2017) 739e742
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom
The Y2S3eLa2S3eGeS2 system at 770 K O.V. Smitiukh a, O.V. Marchuk a, *, I.D. Olekseyuk a, L.D. Gulay b a b
Department of Inorganic and Physical Chemistry, Eastern European National University, Voli Ave 13, 43009 Lutsk, Ukraine Department of Ecology and Protection of Environment, Eastern European National University, Voli Ave 13, 43009 Lutsk, Ukraine
a r t i c l e i n f o
a b s t r a c t
Article history: Received 10 October 2016 Received in revised form 7 December 2016 Accepted 21 December 2016 Available online 23 December 2016
The isothermal section of the Y2S3eLa2S3eGeS2 system at 770 K was investigated. The existence of a solid solution Y4xLa4e4xGe3S12 (x ¼ 0e0.75) was established for the first time. The crystal structure of the Y2La2Ge3S12 compound was studied by X-ray powder method (space group R3c, Pearson symbol hR38, a ¼ 1.92587(9) nm, c ¼ 0.79121(5) nm, RI ¼ 0.0812). Rare-earth atoms M (Y, La) form two types of coordination polyhedra [M1S26S33] and [M2S12S21S32S42] in the crystal structure of Y2La2Ge3S12, and Ge atoms center [GeS11S21S31S41] tetrahedra. © 2016 Elsevier B.V. All rights reserved.
Keywords: Chalcogenides Rare earth compounds Crystal structure X-ray powder diffraction
1. Introduction The interaction of system components with the participation of rare earth metals (REM) is becoming a more common subject among materials scientists of semiconductor industry. These systems enable us to obtain materials with promising semiconductor, crystallographic and physico-chemical characteristics. Such materials feature also unique magnetic and electric properties [1,2]. This work is the first step in the systematic study of the interaction of components in complex sulfide systems R2S3eR0 2S3eDIVS2 (DIV e Si, Ge, Sn; R, R0 e REM) and the crystal structure of the compounds that are formed. According to the literature data, ternary compounds in the boundary quasi-binary system La2S3 e GeS2 form at the ratios of the components 3: 2 (La4Ge3S12), 1: 1 (La2GeS5) and z11: 9 (La3Ge1.25S7). The system Y2S3 e GeS2 features only one compound Y3Ge1.25S7. The crystallographic characteristics of these compounds are given in Table 1. A possibility of the formation of the compound La2Ge2S7 in the La2S3 e GeS2 system was indicated in Ref. [3], but the crystallographic parameters of which are unknown. 2. Experimental details The batches for the investigation were prepared from
* Corresponding author. E-mail address: [email protected] (O.V. Marchuk). http://dx.doi.org/10.1016/j.jallcom.2016.12.283 0925-8388/© 2016 Elsevier B.V. All rights reserved.
elementary individual components of semiconductor purity. The alloy synthesis was performed in evacuated quartz containers in an MP-30 electric muffle furnace according to the following regime: heating to 1420 K (at an of rate 12 K/h), exposure to this temperature for 4 h, cooling to 770 K (12 K/h), homogenizing annealing for 240 h, followed by quenching the synthesized alloys into cold water. Powder diffraction patterns were recorded at a DRON 4-13 Xray diffractometer (CuKa radiation). The data sets of diffraction reflections for X-ray phase analysis of the synthesized alloys were obtained in the 2q range of 10e80 , 0.05 scan step and 5 s exposure in each point. The sets for the determination of the crystal structure of quaternary compounds were recorded in the range of 10e100 , 0.02 scan step, 20 s exposure in each point. Phase analysis of the alloys and the calculation of the crystal structure of quaternary compounds utilized WinCSD software package [8].
3. Results and discussion The performed investigation resulted in the isothermal section of the quasi-ternary system Y2S3eLa2S3eGeS2 at 770 K (Fig. 1). The results of phase analysis of synthesized and annealed alloys confirmed the existence of four ternary compounds La4Ge3S12 (own structure type), La2GeS5 (own structure type), La3Ge1.25S7 (structure type La3CuSiS7) and Y3Ge1.25S7 (structure type La3CuSiS7). The system under these conditions contains in a state of
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Table 1 Crystallographic characteristics of ternary compounds. Compound
Space group
Cell periods, nm
Literature
a
b
c
e e 1.2702 b ¼ 101.39 e
0.5826 0.58120 0.7893
[4] [5] [6]
0.810
[7]
Y3Ge1.25S7 La3Ge1.25S7 La2GeS5
P63 P63 P21/с
0.9730 1.02970 0.7641
La4Ge3S12
R3с
1.940
Fig. 1. The isothermal section of the quasi-ternary system Y2S3eLa2S3eGeS2 at 770 K: 1 e GeS2, 2 e Y2S3, 3 e La2S3, 4 e Y3Ge1.25S7, 5 e La3Ge1.25S7, 6 e La2GeS5, 7 e Y4xLa44xGe3S12 (x ¼ 0e0,75), 8 e GeS2 þ Y3Ge1.25S7, 9 e Y2S3 þ Y3Ge1.25S7, 10 e Y2S3 þ La2S3, 11 e La2S3 þ La3Ge1.25S7, 12 e La3Ge1.25S7 þ La2GeS5, 13 e La2GeS5 þ La4Ge3S12, 14 e GeS2 þ Y4xLa4-4xGe3S12 (x ¼ 0e0.75), 15 e Y3Ge1.25S7 þ Y4xLa4-4xGe3S12 (x ¼ 0e0.75), 16 e Y3Ge1.25S7 þ La2GeS5, 17 e Y2S3 þ La2GeS5, 18 e Y2S3 þ La3Ge1.25S7, 19 e GeS2 þ Y3Ge1.25S7þ Y4xLa4-4xGe3S12 (x ¼ 0.75), 20 e Y3Ge1.25S7 þ La2GeS5 þ La4Ge3S12, 21 e Y2S3 þ La3Ge1.25S7þ La2GeS5, 22 e Y2S3 þ La2GeS5 þ La3Ge1.25S7, 23 e Y2S3 þ La2S3 þ La3Ge1.25S7.
Fig. 2. Variation of the lattice parameters and the unit cell volume of the quaternary compound Y2La2Ge3S12 at 770 K.
Table 2 Results of the crystal structure determination of the Y2La2Ge3S12 compound.
thermodynamic equilibrium 23 phase fields of which 7 are singlephase, 11 are two-phase and 5 are three-phase. We established for the first time the existence of a solid solution range Y4xLa4e4xGe3S12 (x ¼ 0e0.75) of the ternary compound La4Ge3S12 (Fig. 2). The decrease of the parameters a, b and V is explained by the substitution of La atoms with Y atoms with smaller ionic radius. The powder pattern of the sample of the Y2La2Ge3S12 composition resembles closely that of the La4Ge3S12 compound which crystallizes in the trigonal symmetry. Therefore the quaternary phase was considered as one of the compositions of the solid solution. The coordinates of the atoms in the La4Ge3S12 structure were used as a model in the refinement of the crystal structure of Y2La2Ge3S12. Table 2 shows the X-ray experiment conditions and the crystallographic parameters of the quaternary phase. The refinement of the coordinates and isotropic temperature displacement parameters of atoms (Table 3) resulted in satisfactory fit factor values. Interatomic distance in the structure of the compound Y2La2Ge3S12 are shown in Table 4. Experimental and
Space group а (nm) c (nm) V (nm3) Number of atoms in cell Calculated density (g/cm3) Absorption coefficient (1/cm) Radiation and wavelength Diffractometer Mode of refinement Number of atom sites Number of free parameters 2q and sin q/g (max) RI RP Scale factor Texture axis and parameter
(No 161) 1.92587(9) 0.79121(5) 2.5414(4) 114.0 4.1409(7) 667.89 CuKa 1.54185 Powder DRON 4-13 Full profile 7 30 100.02; 0.497 0.0812 0.2139 0.4933(3) [1 1 1 ] 1.95(5)
calculated diffraction patterns of Y2La2Ge3S12 and their difference are shown in Fig. 3.
O.V. Smitiukh et al. / Journal of Alloys and Compounds 698 (2017) 739e742
741
Table 3 Atomic coordinates and isotropic temperature displacement parameters for the La2Y2Ge3S12 compound. Atom
x/a
y/b
z/c
Biso 102, nm2
N
M1a M2a Ge1 S1 S2 S3 S4
0 0.0046(2) 0.1964(2) 0.1581(4) 0.1211(4) 0.1116(5) 0.3928(4)
0 0.2322(1) 0.1862(2) 0.3758(4) 0.0635(4) 0.2013(4) 0.0574(4)
0 0.0183(5) 0.1638(5) 0.1721(11) 0.2440(9) 1.0048(9) 0.1916(10)
0.61(6) 0.38(3) 0.88(9) 0.4(2) 0.4(3) 0.3(3) 1.0(2)
6 18 18 18 18 18 18
a
Occupations: M1 0.91(1) Y þ 0.09(1) La; M2 0.626(9) La þ 0.374(9) Y.
Table 4 Interatomic distances (d) and coordination numbers (C.N.) of atoms in the structure of the compound Y2La2Ge3S12. Atoms M1
M2
Ge
S1
S2
S3
S4
3 3 3 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
S2 S2 S3 S4 S1 S3 S4 S2 S3 S1 S2 S3 S4 S1 Ge1 M2 M2 M2 Ge1 M1 M1 M2 Ge1 M2 M2 M1 Ge1 M2 M2 M2
d (nm)
C.N.
0.2794(6) 0.2860(6) 0.3364(8) 0.2787(9) 0.2880(8) 0.2904(10) 0.2908(8) 0.2949(7) 0.3082(9) 0.3087(9) 0.2160(8) 0.2194(11) 0.2231(8) 0.2303(10) 0.2303(9) 0.2880(8) 0.3087(9) 0.3442(9) 0.2160(8) 0.2794(6) 0.2860(6) 0.2949(9) 0.2194(11) 0.2904(10) 0.3082(9) 0.3364(8) 0.2231(9) 0.2787(9) 0.2908(8) 0.3669(8)
9
Fig. 3. The experimental and calculated diffraction patterns and their difference for the Y2La2Ge3S12 compound.
7
4
4
4
4
4
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Fig. 4. Unit cell and coordination polyhedra in the structure of the compound Y2La2Ge3S12.
In the structure of the quaternary phase the 6c site is occupied by the statistical mixture of Y and La atoms. The coordination surrounding of cations is shown in Fig. 4. M1 atoms (Y, La) center a trigonal prism [M1S26S33] with three additional atoms, M2 (Y, La) coordinate an octahedron [M2S12S21S32S42] with one additional atom, and Ge atoms have octahedral surrounding of sulfur atoms [GeS11S21S31S41]. The lengths of the MeS bonds are additive values as Y and La atoms are in a statistical distribution. The studied quaternary phase is a normal-valence chalcogenide, and can be regarded as a solid solution of the substitution of half the La atoms with Y. References [1] L.D. Gulay, M. Daszkiewicz, Ternary and quaternary chalcogenides of Si, Ge, Sn,
[2] [3]
[4] [5] [6] [7] [8]
Pb, and In, Ch. 250, in: K.A. Gschneidner Jr., J.-C.G. Bünzli, V.K. Pecharsky (Eds.), Handbook on the Physics and Chemistry of Rare Earths, vol. 41, 2011. K. Mitchell, J.A. Ibers, Chem. Rev. 102 (2002) 1929. A.A. Eliseev, G.M. Kuzmichyeva, Phase equilibrium and crystal chemistry in rare earth ternary systems with chalcogenide elements, in: K.A. Gschneidner Jr., J.C.G. Bünzli, V.K. Pecharsky (Eds.), Handbook on the Physics and Chemistry of Rare Earths, vol. 13, 2011, p. 191. А. Michelet, P. Laruelle, J. Flahaut, Comptes Rendus Hebd. des Seances de l'Academie des Sciences, Serie C Sci. Chim. 262 (1966) 753. L.D. Gulay, O.S. Lychmanyuk, Yu. Stepien-Damm, A. Pietraszko, I.D. Olekseyuk, J. Alloys Compds. 414 (2006) 113. H. Zeng, F. Zheng, C.G. Guo, J. Huang, J. Alloys Compds. 458 (2008) 123. A. Mazurier, J. Etienne, Acta Cryst. B 29 (1973) 817. L.G. Aksel'rud, Yu. N. Grin', P. Yu. Zavalij, V.K. Pecharsky, V.S. Fundamensky, Mater. Sci. Forum 133 (1993) 335.
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom
The Y2S3eLa2S3eGeS2 system at 770 K O.V. Smitiukh a, O.V. Marchuk a, *, I.D. Olekseyuk a, L.D. Gulay b a b
Department of Inorganic and Physical Chemistry, Eastern European National University, Voli Ave 13, 43009 Lutsk, Ukraine Department of Ecology and Protection of Environment, Eastern European National University, Voli Ave 13, 43009 Lutsk, Ukraine
a r t i c l e i n f o
a b s t r a c t
Article history: Received 10 October 2016 Received in revised form 7 December 2016 Accepted 21 December 2016 Available online 23 December 2016
The isothermal section of the Y2S3eLa2S3eGeS2 system at 770 K was investigated. The existence of a solid solution Y4xLa4e4xGe3S12 (x ¼ 0e0.75) was established for the first time. The crystal structure of the Y2La2Ge3S12 compound was studied by X-ray powder method (space group R3c, Pearson symbol hR38, a ¼ 1.92587(9) nm, c ¼ 0.79121(5) nm, RI ¼ 0.0812). Rare-earth atoms M (Y, La) form two types of coordination polyhedra [M1S26S33] and [M2S12S21S32S42] in the crystal structure of Y2La2Ge3S12, and Ge atoms center [GeS11S21S31S41] tetrahedra. © 2016 Elsevier B.V. All rights reserved.
Keywords: Chalcogenides Rare earth compounds Crystal structure X-ray powder diffraction
1. Introduction The interaction of system components with the participation of rare earth metals (REM) is becoming a more common subject among materials scientists of semiconductor industry. These systems enable us to obtain materials with promising semiconductor, crystallographic and physico-chemical characteristics. Such materials feature also unique magnetic and electric properties [1,2]. This work is the first step in the systematic study of the interaction of components in complex sulfide systems R2S3eR0 2S3eDIVS2 (DIV e Si, Ge, Sn; R, R0 e REM) and the crystal structure of the compounds that are formed. According to the literature data, ternary compounds in the boundary quasi-binary system La2S3 e GeS2 form at the ratios of the components 3: 2 (La4Ge3S12), 1: 1 (La2GeS5) and z11: 9 (La3Ge1.25S7). The system Y2S3 e GeS2 features only one compound Y3Ge1.25S7. The crystallographic characteristics of these compounds are given in Table 1. A possibility of the formation of the compound La2Ge2S7 in the La2S3 e GeS2 system was indicated in Ref. [3], but the crystallographic parameters of which are unknown. 2. Experimental details The batches for the investigation were prepared from
* Corresponding author. E-mail address: [email protected] (O.V. Marchuk). http://dx.doi.org/10.1016/j.jallcom.2016.12.283 0925-8388/© 2016 Elsevier B.V. All rights reserved.
elementary individual components of semiconductor purity. The alloy synthesis was performed in evacuated quartz containers in an MP-30 electric muffle furnace according to the following regime: heating to 1420 K (at an of rate 12 K/h), exposure to this temperature for 4 h, cooling to 770 K (12 K/h), homogenizing annealing for 240 h, followed by quenching the synthesized alloys into cold water. Powder diffraction patterns were recorded at a DRON 4-13 Xray diffractometer (CuKa radiation). The data sets of diffraction reflections for X-ray phase analysis of the synthesized alloys were obtained in the 2q range of 10e80 , 0.05 scan step and 5 s exposure in each point. The sets for the determination of the crystal structure of quaternary compounds were recorded in the range of 10e100 , 0.02 scan step, 20 s exposure in each point. Phase analysis of the alloys and the calculation of the crystal structure of quaternary compounds utilized WinCSD software package [8].
3. Results and discussion The performed investigation resulted in the isothermal section of the quasi-ternary system Y2S3eLa2S3eGeS2 at 770 K (Fig. 1). The results of phase analysis of synthesized and annealed alloys confirmed the existence of four ternary compounds La4Ge3S12 (own structure type), La2GeS5 (own structure type), La3Ge1.25S7 (structure type La3CuSiS7) and Y3Ge1.25S7 (structure type La3CuSiS7). The system under these conditions contains in a state of
740
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Table 1 Crystallographic characteristics of ternary compounds. Compound
Space group
Cell periods, nm
Literature
a
b
c
e e 1.2702 b ¼ 101.39 e
0.5826 0.58120 0.7893
[4] [5] [6]
0.810
[7]
Y3Ge1.25S7 La3Ge1.25S7 La2GeS5
P63 P63 P21/с
0.9730 1.02970 0.7641
La4Ge3S12
R3с
1.940
Fig. 1. The isothermal section of the quasi-ternary system Y2S3eLa2S3eGeS2 at 770 K: 1 e GeS2, 2 e Y2S3, 3 e La2S3, 4 e Y3Ge1.25S7, 5 e La3Ge1.25S7, 6 e La2GeS5, 7 e Y4xLa44xGe3S12 (x ¼ 0e0,75), 8 e GeS2 þ Y3Ge1.25S7, 9 e Y2S3 þ Y3Ge1.25S7, 10 e Y2S3 þ La2S3, 11 e La2S3 þ La3Ge1.25S7, 12 e La3Ge1.25S7 þ La2GeS5, 13 e La2GeS5 þ La4Ge3S12, 14 e GeS2 þ Y4xLa4-4xGe3S12 (x ¼ 0e0.75), 15 e Y3Ge1.25S7 þ Y4xLa4-4xGe3S12 (x ¼ 0e0.75), 16 e Y3Ge1.25S7 þ La2GeS5, 17 e Y2S3 þ La2GeS5, 18 e Y2S3 þ La3Ge1.25S7, 19 e GeS2 þ Y3Ge1.25S7þ Y4xLa4-4xGe3S12 (x ¼ 0.75), 20 e Y3Ge1.25S7 þ La2GeS5 þ La4Ge3S12, 21 e Y2S3 þ La3Ge1.25S7þ La2GeS5, 22 e Y2S3 þ La2GeS5 þ La3Ge1.25S7, 23 e Y2S3 þ La2S3 þ La3Ge1.25S7.
Fig. 2. Variation of the lattice parameters and the unit cell volume of the quaternary compound Y2La2Ge3S12 at 770 K.
Table 2 Results of the crystal structure determination of the Y2La2Ge3S12 compound.
thermodynamic equilibrium 23 phase fields of which 7 are singlephase, 11 are two-phase and 5 are three-phase. We established for the first time the existence of a solid solution range Y4xLa4e4xGe3S12 (x ¼ 0e0.75) of the ternary compound La4Ge3S12 (Fig. 2). The decrease of the parameters a, b and V is explained by the substitution of La atoms with Y atoms with smaller ionic radius. The powder pattern of the sample of the Y2La2Ge3S12 composition resembles closely that of the La4Ge3S12 compound which crystallizes in the trigonal symmetry. Therefore the quaternary phase was considered as one of the compositions of the solid solution. The coordinates of the atoms in the La4Ge3S12 structure were used as a model in the refinement of the crystal structure of Y2La2Ge3S12. Table 2 shows the X-ray experiment conditions and the crystallographic parameters of the quaternary phase. The refinement of the coordinates and isotropic temperature displacement parameters of atoms (Table 3) resulted in satisfactory fit factor values. Interatomic distance in the structure of the compound Y2La2Ge3S12 are shown in Table 4. Experimental and
Space group а (nm) c (nm) V (nm3) Number of atoms in cell Calculated density (g/cm3) Absorption coefficient (1/cm) Radiation and wavelength Diffractometer Mode of refinement Number of atom sites Number of free parameters 2q and sin q/g (max) RI RP Scale factor Texture axis and parameter
(No 161) 1.92587(9) 0.79121(5) 2.5414(4) 114.0 4.1409(7) 667.89 CuKa 1.54185 Powder DRON 4-13 Full profile 7 30 100.02; 0.497 0.0812 0.2139 0.4933(3) [1 1 1 ] 1.95(5)
calculated diffraction patterns of Y2La2Ge3S12 and their difference are shown in Fig. 3.
O.V. Smitiukh et al. / Journal of Alloys and Compounds 698 (2017) 739e742
741
Table 3 Atomic coordinates and isotropic temperature displacement parameters for the La2Y2Ge3S12 compound. Atom
x/a
y/b
z/c
Biso 102, nm2
N
M1a M2a Ge1 S1 S2 S3 S4
0 0.0046(2) 0.1964(2) 0.1581(4) 0.1211(4) 0.1116(5) 0.3928(4)
0 0.2322(1) 0.1862(2) 0.3758(4) 0.0635(4) 0.2013(4) 0.0574(4)
0 0.0183(5) 0.1638(5) 0.1721(11) 0.2440(9) 1.0048(9) 0.1916(10)
0.61(6) 0.38(3) 0.88(9) 0.4(2) 0.4(3) 0.3(3) 1.0(2)
6 18 18 18 18 18 18
a
Occupations: M1 0.91(1) Y þ 0.09(1) La; M2 0.626(9) La þ 0.374(9) Y.
Table 4 Interatomic distances (d) and coordination numbers (C.N.) of atoms in the structure of the compound Y2La2Ge3S12. Atoms M1
M2
Ge
S1
S2
S3
S4
3 3 3 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
S2 S2 S3 S4 S1 S3 S4 S2 S3 S1 S2 S3 S4 S1 Ge1 M2 M2 M2 Ge1 M1 M1 M2 Ge1 M2 M2 M1 Ge1 M2 M2 M2
d (nm)
C.N.
0.2794(6) 0.2860(6) 0.3364(8) 0.2787(9) 0.2880(8) 0.2904(10) 0.2908(8) 0.2949(7) 0.3082(9) 0.3087(9) 0.2160(8) 0.2194(11) 0.2231(8) 0.2303(10) 0.2303(9) 0.2880(8) 0.3087(9) 0.3442(9) 0.2160(8) 0.2794(6) 0.2860(6) 0.2949(9) 0.2194(11) 0.2904(10) 0.3082(9) 0.3364(8) 0.2231(9) 0.2787(9) 0.2908(8) 0.3669(8)
9
Fig. 3. The experimental and calculated diffraction patterns and their difference for the Y2La2Ge3S12 compound.
7
4
4
4
4
4
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Fig. 4. Unit cell and coordination polyhedra in the structure of the compound Y2La2Ge3S12.
In the structure of the quaternary phase the 6c site is occupied by the statistical mixture of Y and La atoms. The coordination surrounding of cations is shown in Fig. 4. M1 atoms (Y, La) center a trigonal prism [M1S26S33] with three additional atoms, M2 (Y, La) coordinate an octahedron [M2S12S21S32S42] with one additional atom, and Ge atoms have octahedral surrounding of sulfur atoms [GeS11S21S31S41]. The lengths of the MeS bonds are additive values as Y and La atoms are in a statistical distribution. The studied quaternary phase is a normal-valence chalcogenide, and can be regarded as a solid solution of the substitution of half the La atoms with Y. References [1] L.D. Gulay, M. Daszkiewicz, Ternary and quaternary chalcogenides of Si, Ge, Sn,
[2] [3]
[4] [5] [6] [7] [8]
Pb, and In, Ch. 250, in: K.A. Gschneidner Jr., J.-C.G. Bünzli, V.K. Pecharsky (Eds.), Handbook on the Physics and Chemistry of Rare Earths, vol. 41, 2011. K. Mitchell, J.A. Ibers, Chem. Rev. 102 (2002) 1929. A.A. Eliseev, G.M. Kuzmichyeva, Phase equilibrium and crystal chemistry in rare earth ternary systems with chalcogenide elements, in: K.A. Gschneidner Jr., J.C.G. Bünzli, V.K. Pecharsky (Eds.), Handbook on the Physics and Chemistry of Rare Earths, vol. 13, 2011, p. 191. А. Michelet, P. Laruelle, J. Flahaut, Comptes Rendus Hebd. des Seances de l'Academie des Sciences, Serie C Sci. Chim. 262 (1966) 753. L.D. Gulay, O.S. Lychmanyuk, Yu. Stepien-Damm, A. Pietraszko, I.D. Olekseyuk, J. Alloys Compds. 414 (2006) 113. H. Zeng, F. Zheng, C.G. Guo, J. Huang, J. Alloys Compds. 458 (2008) 123. A. Mazurier, J. Etienne, Acta Cryst. B 29 (1973) 817. L.G. Aksel'rud, Yu. N. Grin', P. Yu. Zavalij, V.K. Pecharsky, V.S. Fundamensky, Mater. Sci. Forum 133 (1993) 335.