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AZ9RBAYCAN KIMYA JURNALI № 2 2017
UDC 546 (72.681.682.22) SYNTHESIS AND CRYSTAL STRUCTURE OF THE FeGaInS4 COMPOUND
F.M.Mammadov, N.N.Niftiyev*, F.I.Mammadov**
M.Naqiev Institute of Catalysis and Inorganic Chemistry, NAS of Azerbaijan * Azerbaijan State Pedagogical University **Azerbaijan State Agricultural University
faikmamadov@mail.ru
Received 06.01.2017
The equilibrium alloys of the FeGa2S4-FeIn2S4 system were studied by the method of powder X-ray diffraction. The formation of limited substitutional solid solutions based on the initial ternary compounds and the existence of a quaternary FeGaInS4 compound were established. Based on powder diffraction data, by Rietveld method the crystal structure of the FeGaInS4 compound was refined. It was shown that compound crystallizes in the trigonal system (Sp.gr.P-3m1) with lattice parameters: a = 3.7765(1), c = 12.2257(3) Â, V = 151.00(1) Â3.
Keywords: FeGa2S4-FeIn2S4 system, FeGaInS4, crystal structure.
Introduction
In recent years, magnetic semiconductors of AB2X4 type (where A - Mn, Fe, Co, Ni; B -Ga, In, X - S, Se, Te) have been intensively studied [1-9]. These compounds have unique physical properties, which makes them promising in the manufacture of optoelectronic devices controlled by a magnetic field.
The Ga2S3-FeS system was studied in [10-12]. The FeGa2S4 compound formed in the Ga2S3-FeS system has two modifications: low-temperature trigonal a-phase (Sp.gr. P-3m1) with the lattice parameters a = 3.654, c = 12.056 A and P-phase, which crystallize in an orthorhombic structure (Sr.gr. Pna21) with lattice parameters a=12.98, b=7.49, c=6.09 A. This phase is isostructural with ZnAl2S4 [11]. Both phases are superstructures based on a wurtzite-type structure. The a^P transition occurs at 1327 K. a-FeGa2S4 refers to a structure of the ZnAl2S4 type, however it becomes nonpolar due to the symmetric arrangement of Ga atoms. The package of this structure can be described as follows: ...S=Ga-S=Fe=S-Ga=S... Here, gallium ions are in tetrahedral and iron ions in octahedral positions.
FeIn2S4 compound is formed in the FeS-In2S3 system [13, 14] and crystallizes in the MgAl2O4 (Sp.gr. Fd-3m) structural type with lattice parameter a = 10.61 A.
This work is devoted to the study of the crystal structure of FeGaInS4 by the powder roentgenography method.
Experimental
For the study, ternary compounds FeGa2S4 and FeIn2S4 were synthesized. Synthesis was carried out by melting elementary components of high purity in stoichiometric amounts in evacuated quartz ampoules (~10-2 Pa) in a two-zone inclined furnace. The temperature of the lower "hot" zone was 1470 K, and the upper "cold" ~650 K, which is somewhat below the boiling point of sulfur 718 K.
The purity of the synthesized phases was controlled by DTA and XRD methods.
X-ray diffraction analysis of the synthesized compound FeIn2S4 and FeGa2S4 showed that the crystallographic parameters of these crystals correspond to the literature data.
Alloys of the FeGa2S4-FeIn2S4 system were prepared by melting of the synthesized starting compounds in vacuumed quartz ampoules. In order to achieve an equilibrium state, alloys were annealed at 900 K within 500 h.
The powder X-ray diffraction patterns were recorded on a Bruker D8 ADVANCE difractometer in the 20=10-1200 interval (CuXa-radiation). The X-ray diffraction patterns of the ternary compounds FeIn2S4 and FeGa2S4 were indexed by using the TOPAS-4.2 software. Obtained data were closed to [11] and [13, 14].
Results
The XRD data showed that the FeGa2S4-FeIn2S4 system is characterized by the formation of limited (40 mol.%) solid solutions
based on initial compounds. The alloys with composition 50 mol% FeIn2S4 (FeGaInS4) has a qualitatively new diffraction pattern. It should be noted that the existence of a quaternary Fe-GaInS4 compound was reported by us earlier [7, 9], but the crystal structure of this compound was not determined.
We established that FeGaInS4 compound crystallizes in trigonal system (Sp.gr..P-3m1) with parameters: a = 3.7765(1), c = 12.2257(3) A, V = 151.00(1) A3.
The crystal structure of FeGaInS4 is refined by the Rietveld method based on powder X-ray diffraction using the Topas-4.2 software.
The X-ray diffractogram of FeGaInS4, the intensity difference between the experimental and calculated Rietveld data is shown in Figure 1.
The refined parameters of the unit cell, characteristics of the experimental diffraction peaks, atomic positions, and interatomic distances are collected in Tables 1-4. Figure 2 shows a plan for the three-dimensional structure of FeGaInS4.
As it was noted above, the crystal structure of FeGaInS4 is isostructural with FeGa2S4. However, this is not sufficient for understanding the behavior of the new indium atom in the structure. The gallium atoms in sulphide com-
pounds never take octahedral positions. However, for tetrahedral and octahedral positions, indium atoms are possible. We refined the parameters of the tetrahedral and octahedral positions occupied by indium and iron atoms. A refinement of the structure showed that the In atoms both tetrahedral and octahedral positions are located. At the same time, the percentage of iron atoms to indium corresponds to 81% Fe+19%In. Consequently, tetrahedral positions are occupied by all metals in the ratios (0.5Ga+ 0.19Fe+0.31In). It is easy to see that such a mixed arrangement of atoms better satisfies the local valence balance. We also received an answer to the question: did not the appearance of indium atoms in the structure lead to a violation of its inversion? It is shown, that the polarity in the arrangement of metal atoms in the structure is not revealed. Therefore, we came to the conclusion that FeGaInS4 is crystallizes in the space group P-3m1 as FeGa2S4. It should be noted that the exact values for the temperature factors have not been achieved, which is due to the complicated statistics in filling the positions with metals. Therefore, these parameters were optimized within the specified interval of 0.5<B< 3.0.
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Fig. 1. XRD pattern of the FeGaInS4. Below the diffraction spectrum the difference in the intensities obtained experimentally and calculated by Rietveld is presented.
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F.M.MAMMADOV et al.
Table 1. The refined lattice parameters for the FeGaInS4
Fig. 2. Crystal structure of the FeGaInS4.
Table 2. Characteristics of diffraction peaks of FeGaInS4 compound
20 (°) dhki I, % h k l
7.225 12.2257 9.5 0 0 1
14.479 6.11285 5.3 0 0 2
21.791 4.07523 100 0 0 3
28.223 3.15944 7.0 1 0 1
30.986 2.88374 5.7 1 0 2
35.155 2.55069 3.4 1 0 3
36.726 2.44514 6.7 0 0 5
40.358 2.23308 7.8 1 0 4
44.425 2.03762 5.2 0 0 6
46.325 1.95834 6.6 1 0 5
48.152 1.88825 4.3 1 1 0
52.341 1.74653 7.2 0 0 7
52.899 1.72943 7.8 1 0 6
53.437 1.71327 3.9 1 1 3
56.751 1.62083 3.2 2 0 1
59.999 1.54061 3.3 1 0 7
60.537 1.52821 3.2 0 0 8
67.584 1.38499 3.7 1 1 6
67.610 1.38452 4.0 1 0 8
69.040 1.35929 3.3 2 0 5
69.091 1.35841 3.6 0 0 9
73.852 1.28216 3.3 1 1 7
74.313 1.27535 3.2 2 0 6
75.763 1.25450 5.4 1 0 9
78.110 1.22257 5.5 0 0 10
84.472 1.14597 3.2 2 1 4
84.544 1.14517 3.4 1 0 10
88.622 1.10271 3.2 1 1 9
94.012 1.05315 3.2 3 0 3
94.109 1.05232 4.2 1 0 11
97.212 1.02682 3.4 3 0 4
97.285 1.02624 3.8 1 1 10
104.730 0.97270 4.1 1 0 12
109.987 0.94044 3.4 0 0 13
114.818 0.91426 3.3 2 1 9
Space group P-3m1
Lattice parameters at 298 K, Ä a, Ä c, Ä 3.7765(1) 12.2257(3)
Cell volume, Ä3 151.00(1)
density, g/cm3 3.928(2)
Bregg R, % 4.11
Table 3. Atomic positional parameters in the FeGaInS4
Designation Multiplicity of positions x y z Type of atom and relative occupancy
Mj (Ga+Fe+In) 2 1/3 2/3 0.1945(1) Ga+3 0.50 Fe+2 0.196(3) In+3 0.304(3)
M2 (Fe+In) 1 0 0 0.5 Fe+2 0.804(3) In+3 0.196(3)
S1 2 2/3 1/3 0.1114(4) S 1
S2 2 1/3 2/3 0.3931(4) S 1
Table 4. Interatomic distances in FeGaInS4
M(1) S(2) 3-S(1) 2.429(5) 2.403(2)
M(2) 6-S(2) 2.542(2)
Conclusion
The FeGa2S4-FeIn2S4 system was studied by XRD technique. The formation of a quaternary FeGaInS4 compound was established. The crystal structure of the FeGaInS4 compound was refined using the Rietveld method. It was shown that compound crystallizes in the trigonal system (Sp.gr. P-3m1) with lattice parameters: a = 3.7765(1), c = 12.2257(3) Â, V = 151.00(1) Â3.
References
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FeGaInS4 BiRLOSMOSiMN SiNTEZi УЭ KRiSTAL QURLU§U
F.M.Mammadov, N.N.Niftiyev, F.LMammadov
Rentgenoqrafik analiz ila FeGa2S4-FeIn2S4 sistemi arintilari 6yranilmi§, ilkin komponentlar asasinda avazolunma bark mahlul sahalarinin oldugu va FeGaInS4 dordlu birla§masinin alindigi muayyan edilmi§dir. Bu birla§manin kristal qurlu§u rentgenoqrafik naticalar asasinda Ritveld metodu ila daqiqla§dirilmi§dir. Bela ki, birla§ma triqonal sinqonoyada kristallaijir va qafas parametrlari а=3.7765(1), c=12.2257(3) A, F=151.00(1) A3, faza qrupu P-3m1 kimidir.
Agar sozlar: FeGa2S4-FeIn2S4 sistemi, FeGaInS4, kristal qurulu§.
СИНТЕЗ И КРИСТАЛЛИЧЕСКАЯ СТРУКТУРА СОЕДИНЕНИЯ FeGaInS4
Ф.М.Мамедов, Н.Н.Нифтиев, Ф.И.Мамедов
Методом порошковой рентгенографии изучены равновесные сплавы системы FeGa2S4-FeIn2S4. Установлено образование ограниченных твердых растворов замещения на основе исходных тройных и существование четверного соединения FeGaInS4. На основе порошковых дифракционных данных методом Ритвельда уточнена кристаллическая структура этого соединения, которое кристаллизуется в тригональной сингонии c параметрами решетки: а=3.7765(1), с=12.2257(3) A, F=151.00(1) A3, пространственная группа Р-3т1.
Ключевые слова: система FeGa2S4—FeIn2S4, FeGaInS4, кристаллическая структура.
9. Mamedov F.M.. Niftiev N.N. Dielectric properties of layered FeGaInS4 single crystals in an alternating electric field // Semiconductors. 2016. V. 50. No 9. P. 1203-1207.
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11. Dogguy-Smiri L., Pardo M.P.. Etude cristal-lographique du système FeS-Ga2S3 // Compt. Rend. Acad. Sci.1978. V. 287. P. 415-418.
12. Allazov M.R. The system of FeS-GaS-S // Bulletin of Baku State University. 2009. No 3. P. 42-47.
13. Kanomata T., Ido H., Kaneko T.J. Maqnetic and Cristallographic Studies of MIn2S4(M= Mn.Fe.Co and Ni ) // Phys. Soc. Japan.1973. V. 34. No 2. P. 554-559.
14. Rustamov P.Q., Babaeva B.K., Allazov M.R. State diaqram of FeS-In2S3 // J. of Inorganic Chemistry. 1979. V. 24. No 8. P. 2208-2211.
