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AZERBAIJAN CHEMICAL JOURNAL № 1 2023 ISSN 2522-1841 (Online)
ISSN 0005-2531 (Print)
UDC 546.863.22 + 56.763.24
SYNTHESIS AND PHYSICO-CHEMICAL INVESTIGATION OF ALLOYS OF THE
Sb2S3-Cu2Cr4Te7 SYSTEM
I.LAliyev1, E.I.Mamedov2, F.V.Yusubov2, L.F.Masiyeva2, Kh.M.Gashimov3
M.Nagiyev Institute of Catalysis and Inorganic Chemistry, Ministry of Science and Education
of the Republic of Azerbaijan 2Azerbaijan Technical University 3Azerbaijan State Economic University
aliyevimir@rambler.ru
Received 07.09.2022 Accepted 17.11.2022
To study the nature of the interaction between Sb2S3 and Cu2Cr4Te7 compounds, alloys were synthesized in a wide range of concentrations and studied using physicochemical analysis (DTA, XRD, MSA, as well as measurements of density and microhardness) and a phase diagram was constructed. The state diagram of the system is partially quasi-binary, with the formation of eutectic equilibrium and peritectic transformation. The regions of homogeneity in the Sb2S3-Cu2Cr4Te7 system were determined from the initial components. In a system based on the Sb2S3 compound, solid solutions reach up to 4 mol % Cu2Cr4Te7, and solid solutions based on Cu2Cr4Te7 - up to 10 mol % Sb2S3 at room temperature. The temperature dependence of electrical conductivity and thermo-emf has been studied. 1, 2 and 4 mol % Cu2Cr4Te7 solid solutions of alloys of the Sb2S3-Cu2Cr4Te7 system in the temperature range of 20-2500C.
Keywords: system, phase, density, syngony, component.
doi.org/10.32737/0005-2531-2023-1-162-168
Introduction
When studying the Sb2S3-Cu2Cr4Te7 system, the appearance of photoelectric and magneto-semiconductor phases is likely. There is no information in the literature on phase equilibrium in this system. Antimony chalcogenides and their compounds, as well as alloys in the form of solid solutions, are materials used as energy converters with photoelectric [1-4] and thermoelectric properties [5-7]. Binary and ternary phases based on copper chalcogenides are superionic semiconductors and are used as thermoelectric energy converters, as well as in chemical current sources, in the production of electrochemical sensors [8-13]. Chromium chalcogenides also have photoelectric and magnetic properties [1416]. Based on the foregoing, the study of the interaction of antimony chalcogenides with Cu2Cr4Te7 compounds is relevant, having scientific and practical significance. Previously, we studied systems consis-ting of antimony and chromium chalcogenides [17-21].
The aim of the study was to determine new semiconductor phases and the solid solu-
tion region by constructing a phase diagram of the Sb2S3-Cu2Cr4Te7 system.
Sb2S3 melts with an open maximum at 559.50C and crystallizes in the orthorhombic syngony with lattice parameters: a = 11.229; b = 11 310; c = 3.83 A, sp. gr. Pbnm-D162h, density p = 4.63 g/cm3, microhardness Hp, = 1400 MPa [22]. The Cu2Cr4Te7 compound melts at 1000°C and has a wide homogeneity region [23].
Experimental part
The initial components of the Sb2S3-Cu2Cr4Te7 system were synthesized from high-purity elements: antimony SU-000, high purity sulfur, copper with a purity of 99.998%, chromium with a purity of 99.97%, and tellurium grade B4. Taking into account the peritectic nature of the Cu2Cr4Te7 compound, after synthesis the compound was homogenized for 200 hours at a temperature below the peritectic temperature of15-200C.
Studies of alloys of the Sb2S3-Cu2Cr4Te7 system were carried out by methods of physicochemical analysis: differential thermal analysis (DTA), microstructural analysis (MSA), X-ray
phase analysis (XRD), as well as microhardness measurement and density determination.
The DTA analysis of the alloys was carried out on an NTR-73 low-frequency thermograph. The heating rate was 100/min. X -ray phase analysis of the samples was performed on a D2 PHASER diffractometer. The microstructure was analyzed using a MIM-8 microscope. In the MSA analysis, a solution of H2SO4 + HF = 2:1 was used to determine the phase boundaries; the action time was 20 s. The micro-hardness of the samples was measured by the microhardness of the PMT-3 grade. The density was determined by the pycnometric method using toluene as a liquid. Measurement of electrical conductivity and thermo-EMF was carried out by the usual compensation method [24, 25]. The samples used were in the form of a parallelepiped. The experimental error was 2.7-3.0 %.
Results and their discussion
The alloys of the Sb2S3-Cu2Cr4Te7 system represent the substance of gray color obtained in a compact form. Alloy systems are resistant to air, water and organic solvents. Mineral acids (HNO3, H2SO4) strongly destroy them. The specimens were subjected to heat treatment at 4000C for 250 h to bring them to a state of equilibrium.
The differential-thermal analysis of the alloys shows that all endothermic effects on the heating and cooling curves are reversible. The thermograms of the alloys revealed two and three endothermic effects. A large number of thermal effects in the system indicates a complex interaction. After homogenization, the microstructure of the alloys was analyzed and it was found that there are homogeneous areas near the initial components, and the rest of the alloys are two-phase. To refine the obtained phases, microstructural analysis was performed (Figure 1).
On Figure 1 shows the microstructure of alloys containing 4, 70 and 90 mol % u2Cr4Te7.
Single-phase samples containing 4 and 90 mol % Cu2Cr4Te7 are their solid solutions based on Sb2S3 and Cu2Cr4Te7. Sample 70 mol % Cu2Cr4Te7 refers to the two-phase region. To confirm the reliability, an X-ray phase analysis
of the alloys was carried out (Figure 2). As can be seen from the Figure 2, diffraction pattern 90 mol % Cu2Cr4Te7 are identical to the diffraction patterns of the Cu2Cr4Te7 compound, differing only slightly in interplanar spacings. This sample represents solid solutions based on Cu2Cr4Te7. Sample 4 mol % Cu2Cr4Te7 with its content is its solid solution based on the Sb2S3 compound. Diffraction lines are present on the diffraction patterns of alloys 70 mol % Cu2Cr4Te7, consisting of a mixture of diffraction lines of the initial components. That is, these samples are two-phase. Thus, the results of X-ray phase analysis confirm the results of differential thermal and microstructural analysis.
Based on the results of these physico-chemical methods of analysis, the phase diagram of the Sb2S3-Cu2Cr4Te7 system was constructed (Fig. 3). In the Sb2S3-Cu2Cr4Te7 system, the solubility of Sb2S3 at room temperature is 4 mol %, and the solubility based on Cu2Cr4Te7 is 10 mol % Sb2S3. It is known that near the Cu2Cr4Te7 compound there is a large solid solution region. Above 1000°C the compound decomposes Cu2Cr4Te7^L + Cr2Te3 by the next reaction. The liquidus of the Sb2S3-Cu2Cr4Te7 system is surrounded by monovari-ant curves of phase a and Cr2Te3. At this point, a three-phase equilibrium reaction takes place: L^ a + Cr2Te3. The result is in the range of concentrations 10-35 mol % Cu2Cr4Te7 forms a three-phase field L+a+Cr2Te3. Under the soli-dus line in the range of concentrations Cu2Cr4Te7 4-90 mol % two-phase alloys (a + P) crystallize. In the Table 1 some physical and chemical properties of alloys of the system Sb2S3-Cu2Cr4Te7 are given.
The samples synthesized for physical measurements were made in the form of a parallelepiped with dimensions of 1.0*0.5*1.5 cm. The temperature dependence of electrical conductivity and thermo-emf has been studied 1, 2 and 4 mol % Cu2Cr4Te7 solid solutions of alloys of the Sb2S3-Cu2Cr4Te7 system. The temperature dependence of the electrical conductivity of the samples was measured by the compensation method in the temperature range 20-25 00C.
Fig. 1. Microstructure of alloy systems Sb2S3-Cu2Cr4Te7. 1 - 4, 2 -70, 3 - 90 mol % Cu2Cr4Te7.
I
1000 -i 800 -600 -400 200 H
10
20
30
40 26
50
60
70
Fig. 2. Diffractograms of alloy systems Sb2S3-Cu2Cr4Te7. 1-Sb2Ss, 2-70, 3-90, 4-100 mol % C^C^Tev.
t,°C 1200
1000
800
600 ,
400
200
1210o
1000o
Sb2S3
20
40 60 mol %
80 Cu2Cr4Te7
Fig.3. Phase diagram of the system Sb2S3-Cu2Cr4Te7.
Composition of alloys of the Sb2S3-Cu2Cr4Te7 system, DTA results, microhardness and density determination results
Composition, mol % Thermal effects, oC Density, g/cm3 Microhardness, MPa
a ß
Sb2S3 Cu2Cr4Te7
P=0.10 N P=0.15 N
100 0.0 550 4.63 1400 -
95 5.0 490,550 4.75 1430 -
90 10 470,550 4.88 1460 -
85 15 455,450 4.99 1460 -
80 20 455,525 5.12 1460
70 30 455,490,700 5.37 1460 -
65 35 455,750 5.49 - -
60 40 550,810 5.62 - -
50 50 455,670,900 5.86 - -
40 60 455,770,990 6.11 - 2000
30 70 455,850,1050 6.36 - 2000
20 80 455,900,1120 6.61 - 2000
10 90 570,950 6.85 - 2000
5.0 95 775,980 7.05 - 1990
0.0 100 1000,1120 7.10 - 1970
Temperature dependence of the electrical conductivity of solid solutions of alloys containing 1, 2, and 4 mol % Cu2Cr4Te7 is shown in Fig. 4. As shown in Figure 4, adding Cu2Cr4Te7 to Sb2S3 increases the electrical conductivity depending on temperature and composition. Ad-
ding 1, 2 and 4 mol % Cu2&4Te7 to the Sb2S3 compound leads to defect filling and an increase in conductivity as the carrier concentration increases. As can be seen from the temperature dependence of the electrical conductivity of the (Sb2S3)1-x(Cu2Cr4Te7)x solid solution, all alloys
are semiconductor. Their electrical conductivity increases with temperature, just like semiconductors. When 1 mol % Cu2Cr4Te7 is added to the Sb2S3 compound, the electrical conductivity takes the following values from room tem-0 8 perature to 250 C, respectively: o=5.6310- ,
20.210-7 Om-1sm-1.
The electrical conductivity increases relatively slightly in the temperature range of 20-1200C, and the electrical conductivity in this range corresponds to the impurity electrical
conductivity. In the temperature range of 100-1200C, intrinsic conductivity begins, and with a further increase in temperature, the electrical conductivity increases significantly. In the intrinsic conduction region, the number of electrons and holes is equal.
The value of the electrical conductivity of
samples with 2 and 4 mol. % Cu2Cr4Te7 is at
8 8 11 room temperature o=7.110- , 17.810- Om- cm-,
0 7
respectively, and at 2500C, o = 31.610-7 and 50.110-7 Om-1cm-1 (Figure 4).
lgo, Om"1sm"1 M+a
-5.5 -6.0 -6.5 -7.0
-7.5
2.0
2.5 3.0 103/T,K
3.5
a, 10-4 V/K
16
14
12
10
_J_|_!_L_
2.0
2.5
3.0 103/T,K
3.5
Fig.4.Temperature dependence of electrical conductivity (g) (Sb2S3)1-x(Cu2Cr4Te7)x (x = 0,01; 0,02; 0,04) solid solutions of alloys: 1 - 1, 2 - 2, 3-4 mol % Cu2&4Te7.
F ig.5. Temperature dependence of thermo-emf (a) (Sb2S3)1-x(Cu2Cr4Te7)x (x = 0,01; 0,02; 0,04) solid solutions of alloys: 1 - 1, 2 - 2, 3 - 4 mol % Cu2Cr4Te7.
From the plot of the electrical conductivity of the samples, the band gap of the samples was calculated based on the angle tga, divided by the touch log o ~ f (103/T) on the temperature curve of the graph of additive and specific conductivity. Temperature dependence of ther-mo-emf 1, 2 and 4 mol % Cu2Cr4Te7 solid solution alloys (Sb2S3)1-x(Cu2Cr4Te7)x is shown in Figure 5.
As can be seen from the graphical temperature dependence of the temperature de-
pendence of thermo-emf a ~ (T), this dependence consists of two parts in the temperature range of 20-2500C.
In the temperature range of 20-250°C for solid solutions of (Sb2S3)1-x(Cu2Cr4Te7)x (x = 0.01; 0.02; 0.04) alloys, the thermo-emf value, depending on temperature, first reaches a maximum value, then decreases, and depending on the composition increases (Figure 5).
For samples with compositions 1, 2 and 4 mol. % Cu2Cr4Te7 at room temperature thermo-
emf is a = 10.2510-4 V/K, a = 11.0510-4 V/K and a = 11.7510-4 V/K respectively. At a temperature of 1200C, the maximum values of thermo-emf of the samples are a = 13.1210-4, 14.3010-4 and 15.5210-4 V/K respectively. With a subsequent increase in temperature, the thermo-EMF values drop sharply.
The difference in the calculated values of the electrical conductivity and thermo-electric power of alloys of the solid solution (Sb2S3)1-x (Cu2Cr4Te7)x (x = 0.01; 0.02; 0.04) is also due to the properties of the second component, which is part of the composition and mass the number of the element depends.
Conclusion
The chemical interactions of Sb2S3-Cu2Cr4Te7 were studied using modern phy-sicochemical methods of analysis: differrential thermal analysis (DTA), X-ray phase analysis (XRD), microstructural analysis (MCA), as well as determination of microhardness, density, and its phase diagram was constructed. The phase diagram of the system is partially quasi-binary and is characterized by eutectic equilibrium and peritectic transformation. In the Sb2S3-Cu2Cr4Te7 system based on the Sb2S3 compound, solid solutions reach up to 4 mol % Cu2Cr4Te7, and solid solutions based on Cu2Cr4Te7 - up to 10 mol % Sb2S3 at room temperature. The temperature dependence of electrical conductivity and thermo-emf has been studied. 1, 2 and 4 mol. % Cu2Cr4Te7 solid solutions of alloys of the Sb2S3-Cu2Cr4Te7 system in the temperature range of 20-2500C.
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Sb2S3-Cu2Cr4Te7 SiSTEMiNiN ORiNTÎLORÎNÎN SiNTEZi УЭ FiZiKi-KiMYOVi TODQiQi
i.i. Oliyev, E.i. Mammadov, F.V.Yusubov, L.F. Masieva, X.M.Ha§imov
Sb2S3 va Cu2Cr4Te7 birlaçmalari arasindaki qarçiliqli tasirlarin oyranilmasi uçun geniç qatiliq sahasinda numunalar sintez edilmiç va fiziki-kimyavi analiz metodlari vasitasila (DTA, RFA, MQA, hamçinin sixliq va mikrobarkliyin olçulmasi) tadqiq edilmiç va faza diaqrami qurulmuçdur. Sistemin faza diaqrami evtektik tarazliq va peritektik çevrilma ila xarakteriza olunur. Sb2S3-Cu2Cr4Te7 sistemda ilkin komponentlar asasinda otaq temperaturunda Sb2S3 asasinda 4 mol % bark mahlul sahasi oldugu halda, Cu2Cr4Te7 birlaçmasi asasinda isa 10 mol % hallolma sahasi muayyan edilmiçdir. Sb2S3-Cu2Cr4Te7 sisteminin 1, 2 va 4 mol % Cu2Cr4Te7 bark mahlul arintilarinin elektrik keçiriciliyinin va termo-ehq-nin temperatur asililigi 20-2500C temperatur intervalinda ôyranilmiçdir.
Açar sozlzr: sistem, faza, sixliq, sinqoniya, komponent.
СИНТЕЗ И ФИЗИКО-ХИМИЧЕСКОЕ ИССЛЕДОВАНИЕ СПЛАВОВ СИСТЕМЫ Sb2S3-Cu2Cr4Te7
И.И.Алиев, Э.И.Мамедов, Ф.В.Юсубов, Л.Ф.Масиева, Х.М.Гашимов
Для изучения характера взаимодействия соединений Sb2S3 и Cu2Cr4Te7 были синтезированы сплавы в широком диапазоне концентраций и изучены с помощью физико-химического анализа (ДТА, РФА, МСА, а также измерения плотности и микротвердости) и построена фазовая диаграмма. Диаграмма состояния системы частично квазибинарная, с образованием эвтектического равновесия и перитектического превращения. В системе на основе соединения Sb2S3 твердые растворы доходит до 4 мол. % Cu2Cr4Te7, а твердые растворы на основе Cu2Cr4Te7 - до 10 мол. % Sb2S3 при комнатной температуре. Исследована температурная зависимость электропроводности и термо-эдс 1, 2 и 4 мол. % Cu2Cr4Te7 твердые растворы сплавов системы Sb2S3-Cu2Cr4Te7 в интервале температур 20-2500С.
Ключевые слова: система, фаза, плотность, сингония, компонент.
