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376 CHEMICAL PROBLEMS 2020 no. 3 (18) ISSN 2221-8688
<S
UDC 546. 19.22+56.763.24
CHEMICAL INTERACTION AND GLASS FORMATION IN THE As2S3-CuCr2Te4 SYSTEM
I.I. Aliev1, M.G. Shakhbazov2, S. Sh. Ismailova1
1Acad. M.F. Nagiyev Institute of Catalysis and Inorganic Chemistry National Academy of Sciences of Azerbaijan e-mail: aliyevimir@rambler.ru 2Azerbaijan Pedagogical State University 34 Hajibeyov str., Baku AZ1001
Received 29.06.2020 Accepted 08.09.2020
The character of the chemical interaction and glass formation in the As2S3-CuCr2Te4 system was explored by means of physicochemical analysis (DTA, MSA, XRD, density and microhardness measurements) and a phase diagram was constructed. It was established that the state diagram of the system is a quasi-binary eutectic type. In the system narrow homogeneous regions of up to 1.5 mol % As2S3 and 3.5% mol % CuCr2Te4 were detected. Compounds As2S3 and CuCr2Te4 with each other form a eutectic composition of 10 mol. % CuCr2Te4 with a melting point of270oC. Under ordinary conditions, in the As2S3-CuCr2Te4 system based on As2S3, the glass-forming region reaches 15 mol % CuCr2Te4. Keywords: eutectic, glass formation, density, microhardness, syngony. DOI: 10.32737/2221-8688-2020-3-376-381
Introduction
The glassy chalcogenides AS2S3 and As2Se3 and alloys doped with some chalcogenides as photosensitive and magneto-optical materials have attracted the attention of researchers in recent years [1-8]. In this regard, multicomponent systems with the participation of arsenic sulfide and selenide are intensively studied [9-11]. Chromium chalcogenides and the obtained ternary compounds based on it have magnetic properties [12-14]. Therefore, the study into interaction between As2Se3 and CuCr2Te4 compounds is very important.
The aim of this work is to study chemical interactions and glass formation in the As2S3-CuCr2Te4 system and build a phase
diagram.
The glassy compound As2S3 melts with open maximum at 310°C and crystallizes in monoclinic syngony with lattice parameters as follows: a = 11.49; b = 9.59; c = 4.25 A, p = 90o27/, sp.gr. P 21/n [15]. The density and microhardness of the glassy As2S3 compound are respectively p = 3.187 g/cm3 and Hp, = 128-145 MPa.
The initial compound CuCr2Te4 melts congruently at 1155°C [14] and crystallizes in a cubic syngony with lattice parameters a = 11.134 A, sp.gr. Fd-3m, density p = 6.51 g/cm3 [16].
Experimental part
The alloys were annealed at 270°C for 350 hours. Alloys of the system were obtained from ligatures As2S3 and CuCr2Te4, previously synthesized from elements in quartz ampoules pumped out to 0.133 Pa in the range of temperature 600-1200oC depending on the alloy composition. The alloys were annealed at 270°C for 350 hours.
The alloys of the As2S3-CuCr2Te4 system were studied by differential thermal (DTA), X-ray diffraction (XRD), microstructural (MSA) analysis, as well as microhardness measurements and density determination.
Thermal analysis of the alloys was carried out on a TERMOSKAN-2 instrument
CHEMICAL PROBLEMS 2020 no. 3 (18)
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with accuracy of 3-5°C, whiht chromel-alumel thermocouple. The heating rate is 5 deg/min. X-ray phase analysis was performed on an X-ray device of D2 PHASER model using CuKa radiation and a Ni filter. Microstructural analysis of alloys of the As2S3-CuCr2Te4
system was carried out by means of a MIM-8 microscope. The microhardness of the phases was measured on a PMT-3 instrument with accuracy of 5% while the density of the samples was determined by the pycnometric method.
Results and its discussion
Alloys of the As2S3-CuCr2Te4 system with high As2S3 content are bright red, brittle layered, and with the CuCr2Te4 increased content; the samples acquire a dark brown hue. Alloys rich in As2S3 are obtained by a glassy appearance. They are resistant to air and water. Concentrated mineral acids (HNO3, H2SO4) and alkalis (NaOH, KOH) decompose them. In
order to crystallize glassy alloys, 0-25 mol % of As2S3-based CuCr2Te4 was annealed at 170° C for 600 hours while the remaining alloys were annealed at 300°C for 240 hours. A physicochemical study was performed before and after annealing. Some physicochemical properties of alloys from the glass region are given in Table 1.
Table 1. Some physicochemical properties of glasses of the As2S3-CuCr2Te4 system
Composition, mol % Thermal effects, oC Microhardness, MPa Density q/cm3 Results MSA
As2S3 CuCr2Te4 Tg TKp. Tnn.
100 0 170 230 310 1350 3,20 Glass,
97 3 170 230 210 1380 3,25 —
95 5 175 240 315 1380 3,32 —
93 7 180 245 320 1380 3,39 —
90 10 190 250 275 1390 3,47 —
85 15 195 255 320 1400 3,58
80 20 200 260 330 1420 3,70 —
75 25 210 270 340 1430 3,83 Glass, crystal.
70 30 210 275 350 1450 3,96 Glass, crystal.
60 40 220 280 350 1450 4,25 Glass, crystal.
Thermal analysis of alloys of the As2S3-CuCr2Te4 system showed that thermograms of alloys are observed two endothermic effects related to solidus and three endothermic effects related to liquidus. DTA of the system alloys before annealing shows that on thermograms of the alloys in the concentration range of 0-25 mol. % CuCr2Te4, a softening temperature is observed at Tg of 170°C. After prolonged heat treatment at 170 ° C for 600 h, the alloys crystallize and a series of effects is observed on the thermograms.
a) b) c)
Fig. 1. Microstructure of alloys of the As2S3-CuCr2Te4 system. a) - 1.5; b) -90.; c) - 96.5 mol % CuCr2Te4.
Microstructural analysis of the alloys of the As2S3-CuCr2Te4 system shows that, in addition to the initial components, the remaining alloys are biphasic. The microstructure of alloys from the region of 0-15 mol % CuCnTe4 represents one phase of dark color, and in the concentration range from 15 to 25 mol. % CuCr2Te4 crystalline inclusions appears. A study of the microstructure of the annealed samples showed that 1.5 mol % CuCr2Te4 and 3.5 mol. % As2S3 single-phase alloys (Fig. 1a and c). As the content of CuCr2Te4 rises to 10 mol. % As2S3 solid solutions disintegrate and the alloys become biphasic (Fig. 1 b)
RAF of unannealed alloys of the As2S3-CuCr2Te4 system shows that only on thermograms of cast samples with a content of more than 25 mol. % CuCr2Te4, intense diffraction lines are observed. After annealing at 170°C for 600 hours on diffraction patterns in
the concentration range of 0-25 mol % CuCr2Te4 intense diffraction maxima are obtained. X-ray analysis showed that the diffraction patterns of alloys 70 and 100 mol % CuCr2Te4 consist of mixed diffraction lines of the starting components. These data confirm that the alloys of the system are two-phased. Fig. 2 shows diffraction patterns of alloys in the system of compositions 10, 15, 25, 70, and 100 mol % CuCr2Te4. As seen in Fig. 1, alloys 10, 15 mol % CuCr2Te4 belongs to the field of glasses, 25 mol % CuCr2Te4 in the glass-crystalline region, 70 and 100 mol % CuCr2Te4 crystalline region.
DTA, XRD and MSA showed that in the system with slow cooling of the samples, the region of glass formation reaches 15 mol % CuCr2Te4, as well as in the regime of quenching in ice water of about 20 mol % CuCr2Te4.
I % 1000 800 '
600' 400 j 200
/V
............
10
20
30
40
50
60
70
29
Fig. 2. Diffraction patterns of alloys of the As2S3-CuCr2Te4 system. 1-10, 2-15, 3-25, 4-70, 5-100 mol % CuCr2Te4.
The T-x phase diagram of the As2S3-CuCr2Te4 analysis is shown in Fig. 3. The state diagram of system built in line with the physicochemical the As2S3-CuCr2Te4 system is a quasi-binary
eutectic type (Fig. 3).
1
t,oC 1200
1000 -
800 -
600 -
400 "
200 "
1155o
810o
AS2S3
20
40 60
moïï. %
80 CuCr2Te4
Fig. 3. T-x phase diagram of the As2S3-CuCr2Te4 system. Area of glass formation: 1-slow cooling, 2-quenching in ice water.
The liquidus of the system consists of 96 mol % CuCr2Te4 concentrations below the
monovariant curves of ô, a and P-phase. The phases ô and a form an eutectic with composition of 10 mol % CuCr2Te4 and melt at 270 ° C. At the eutectic point, a three-phase reaction occurs: ^^ ô + a. In the range of 1.5-
solidus line, two-phase alloys crystallize (ô + a). In the range of 96.5-100 mol % CuCr2Te4 crystallizes a phase. The microhardness of As2S3-CuCr2Te4 alloys was measured at each phase before and after annealing.
Table 2. Results of DTA measurements of microhardness and density of system alloys
As2S3-CuCr2Te4 after annealing
Composition, mol % Thermal effects, oC Density, g/cm3 Microhardness, MPa
a B
As2S3 CuCr2Te4
P=0,10 H P=0,15 H
100 0.0 310 3,46 700 -
95 5,0 270,310 3,60 750 -
90 10 270 3,76 Eutec. Eutec.
85 15 270,375 3,92 - -
80 20 270,480 4,07 800 -
70 30 270,615 4,37 800 -
60 40 270,615,720 4,68 - -
50 50 270, 615,800 4,98 - -
40 60 270,860 5,28 - 1870
30 70 270,925 5,60 - 1870
20 80 270,1000 5,90 - 1880
10 90 830,1075 6,21 - 1880
5,0 95 700,1120 6,57 - 1880
3,0 97 1130 6,54 - 1860
0,0 100 810,1155 6,51 - 1850
When measuring the microhardness of the system alloys, three series of values were obtained (Table 1). Before annealing, the microhardness of glassy alloys 0-10 mol % CuCr2Te4 in the range of microhardness varies in the range (1350-1400) MPa. After annealing the same alloys, the microhardness decreases (700-800) MPa. The microhardness of a phase (CuCr2Te4-based solid solutions) varies in the range (1850-1880) MPa. Prior to annealing, the density values of glassy alloys in the
concentration range of 0-20 mol % CuCr2Te4 vary in the range of 3.20-3.70 g/cm3 (Table 2). After annealing, the density values of the alloys in the same region vary within 3.46-3.93 g/cm3 (Table 2). The data obtained show that the microhardness of glasses is higher than the corresponding crystals. On the contrary, the density of glasses is lower than that of the corresponding crystals, which is in good agreement with the literature.
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As2S3-CuCr2Te4 SÍSTEMÍNDe KiMYeVÍ QAR§ILIQLI T3SÍR уэ §ü§eeMeLeGeLMe
i.i. eliyev, M.G. §ahbazov, S. ísmayilova
AMEA-nin akad. M.Nagiyev adina Kataliz vd Qeyri-üzvi Kimya institutu AZ1143, Baki, H.Cavidpr., 113; e-mail: aliyevimir@rambler.ru Azdrbaycan Dovldt Pedaqoji universiteti AZ 1001 Baki, Ü.Hacibdyov küg.34
As2S3-CuCr2Te4 sistemindd kimydvi qar§iliqli tdsir vd §ü§ddmldgdlmdnin xüsusiyydtldri fiziki-kimydvi analiz metodlari (DTA, MSA, XRD, hdmginin sixliq vd mikrobdrkliyin olgmdldri) ild tddqiq edilmi§ vd faza diaqrami qurulmu§dur. Ndticddd müdyydn edilmi§dir ki, sistemin hal diaqrami kvazibinar olub, evtektik tiplidir. Sistemdd As2S¡ yaxinligindaki, 1.5 mol % -d qdddr mdhdud sahddd bdrk mdhlul sahdsi movcuddur, CuCr2Te4 birld§mdsi dsasinda isd 3.5 mol % bdrk mdhlul a§kar edilmi§dir. As2S¡ vd CuCr2Te4 birld§mdldri arasinda dmdld gdldn evtektikanin tdrkibi 10 mol % CuCr2Te4 vd drimdsi isd 270°C-dir. As2S¡-CuCr2Te4 sistemindd adi soyudulma §draitindd, As2S3 dsasinda §ü§d sahdsi 15 mol % CuCr2Te4 td§kil edir. Agar sozfor: evtektik, §ü§ddmdldgdlmd, sixliq, mikrobdrklik, sinqoniya.
ХИМИЧЕСКОЕ ВЗАИМОДЕЙСТВИЕ И СТЕКЛООБРАЗОВАНИЕ В СИСТЕМЕ As2Sз-СuCr2Тe4
И.И. Алиев, М.Г. Шахбазов, С.Ш. Исмаилова
Институт катализа и неорганической химии им. акад. М.Нагиева Национальной АН Азербайджана AZ1143 Баку, пр. Г.Джавида, 113; e-mail:aliyevimir@rambler.ru Азербайджанский Государственный Педагогический университет AZ1001 Баку, ул. У. Гаджибекова, 34
Характер химического взаимодействия и стеклообразования в системе As2S3-CuCr2Te4 исследован методами физико-химического анализа (ДТА, МСА, РФА а также измерением плотности и микротвердости) и построена фазовая диаграмма. Установлено, что диаграмма состояния системы является квазибинарной эвтектического типа. В системе выявлены узкие гомогенные области до 1.5 мол. % As2S3 и 3.5 мол. %. CuCr2Te4. Соединения As2S3 и CuCr2Te4 между собой образуют эвтектику состава 10 мол. % CuCr2Te4 с температурой плавления 270oC. При обычных условиях охлаждения в системе As2S3-CuCr2Te4 на основе As2S3 область стеклообразования доходит до 15 мол. % CuCr2Te4.
Ключевые слова: эвтектика, стеклообразование, плотность, микротвердость, сингония.
