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ISSN 2522-1841 (Online) AZERBAIJAN CHEMICAL JOURNAL № 2 2022 ISSN 0005-2531 (Print)
UDC 546.19.22-666.22
PHASE EQUILIBRIUM AND GLASS FORMATION IN THE AsS-ErS SYSTEM
T.M.Ilyasly, D.T.Hasanova, I.I.Aliyev*
Baku State University *M.Nagiyev Institute of Catalysis and Inorganic Chemistry, NAS of Azerbaijan
Received 16.12.2021 Accepted 26.01.2022
Phase equilibrium and glass formation between AsS and ErS compounds were studied by methods of physicochemical analysis: differential-thermal (DTA), X-ray phase (XRD), microstructural analysis (MSA), as well as by measuring microhardness and density. The T-x phase diagram of the AsS-ErS system was constructed. It has been established that the phase diagram of the AsS-ErS system is quasi-binary, of the eutectic type and is characterized by the formation of the chemical compound ErAsS2. The ErAsS2 compound is formed as a result of the peritectic reaction M+ErS-^- ErAsS2 at 7500C and crystallizes in the tetragonal syngony with lattice parameters: a=13.62; c=18.93 A; ppuc= 5.17 g/cm3, pX-ray= 5.21 g/cm3. The eutectic composition between the AsS and ErS compounds is 10 mol % ErS and a temperature of 280oC. Under normal cooling conditions, the area of glass formation based on AsS reaches 10 mol % ErS. For glass alloys, some physicochemical properties have been studied. Solubility based on AsS reaches up to 1.5 mol % ErS, and based on ErS, the solubility is practically not established.
Keywords: phase, glass formation, microhardness, liquidus, syngony.
doi.org/10.32737/0005-2531-2022-2-87-92 Introduction
Glassy arsenic chalcogenides and alloys based on them are widely used in electronic engineering, radio engineering, IR optics, and color television as photosensitive materials [1-8]. At present, light-sensitive fibers based on arsenic chalcogenides As2S3, As2Se3 are used in microelectronics [9-14]. REE chalcogenides and alloys derived from them are complex semiconductors with photosensitive, thermoelectric, magnetic, and luminescent properties [15-21].
The creation of physicochemical bases for obtaining a multicomponent complex chal-cogenide glassy phase of variable composition is one of the most important tasks of chemistry and physics. To solve these problems, it is necessary to study the chemical interaction between the components of the corresponding systems and construct their phase diagrams.
This work is devoted to the physico-chemical study of the AsS-ErS system to obtain new three-component glassy and crystalline sulfide phases.
The AsS compound melts congruently at 3180C and crystallizes in a rhombic system
with lattice parameters: a=9.32; ¿=13.546; c=6.585 A [22].
The ErS compound melts congruently at 21800C and crystallizes like NaCl in the cubic system with lattice parameters: a=5.424 A, sp.gr. Fm3m, density dpycn= 6.75 g/cm3, dX-ray= 7.10 g/cm3 [23] .
Experimental part
Synthesis of the initial compounds and alloys of the studied AsS-ErS systems was carried out by fusion of the initial components in evacuated quartz ampoules in the temperature range of 500-1100°C. Alloys of the system in the concentration range 0-30 mol % ErS under normal conditions are obtained in a glassy and glassy-crystalline form. For the crystallization of glassy alloys, long-term annealing was carried out at 2300C for 750 h.
Equilibrium alloys were studied by DTA, XPA, MSA, as well as by measuring microhardness and density.
The differential thermal analysis of the alloys of the system was carried out on a TERMOSCAN-2 device with a heating rate of 5 deg/min.
X-ray phase analysis was performed on a D2 PHASER X-ray device using CuKa radiation with a Ni filter. MCA of the alloys of the system was carried out using a MIM-8 metallographic microscope. When studying the microstructure of the alloys, an etchant of the composition 10 ml NaOH + 5 ml H2O2 =1:1 was used, and the etching time was 15-20 s. The microhardness of the alloys of the system was measured on a PMT-3 microhardness tester at a load of 0.10 N. The density of the alloys of the system was determined by the pycnometric method; toluene was used as the working fluid.
Results and discussion
DTA of cast samples of the AsS-ErS system in the concentration range of 0-30 mol % ErS showed that on the thermograms of these alloys there are effects corresponding to the softening temperature Tg. After annealing, these peaks disappear in the thermograms of the same alloys of the system. softening temperature. The MCA of the alloys of the system showed that in the concentration range of 0-10 mol % ErS
samples are glassy. Alloys within 10-30 mol % ErS are glass-ceramic samples. The physico-chemical study of the alloys of the system was carried out before and after annealing.
Thermal analysis of alloys of the AsSErS system after annealing showed that two and three endothermic effects are observed on the thermograms.
The microstructures of alloys of the AsSErS system show that, near AsS, the alloys are single-phase, and the rest are two-phase. In the AsS-based homogeneity system, it reaches 1.5 mol % ErS, and based on ErS the solubility has not been established.
In order to clarify the region of glass formation, X-ray diffraction analysis was performed before and after annealing. The results showed that on the diffraction patterns of the alloys of the system before annealing in the concentration range of 0-30 mol % ErS, no strong diffraction peaks were found, and after annealing, significant diffraction peaks appear (Figure 2).
I
1 000 -800-600-400 -
2po;
1000 800 600 -400 -200 "
jL
,. a ,—_v
ErAsS2
2 4
i
i
10
20
30 40
20
50
60
Fig. 1. Diffractograms of alloys of the AsS-ErS system: 1 - 5, 2 - 10, 3 - 25, 4 - 50, 5 - 100 mol % ErS.
5
t,oC 2200
1800
1400
1000
800
600
400
200
- **
✓
L y s
- L+ ErS
_ 750°
L+a/ L+ErAsS2
a f " 280o ErAsS2+ErS
1 ÜönacTb a+ErAsS2
krej_ i i i i i i
2180°
AsS
20 40
mol %
60
80 ErS
Fig. 2. Phase diagram of the AsS-ErS system.
Taking into account the conchoidal fracture, the presence of thermal effects of softening temperatures on the thermograms, and the absence of diffraction peaks on the diffraction patterns, one can judge glasses. Conducted X-ray diffraction analysis of alloys containing 5, 10, 25, 50 and 70 mol. % ErS (Figure 1). Alloys containing 5, 10 mol % ErS were obtained in the glassy state. On the diffraction pattern of the alloy 50 mol % ErS, the diffraction lines differ in intensity and interplanar distances from the diffraction patterns of the initial components. Sample composition 50 mol % ErS corresponds to the formula ErAsS2. Diffraction lines in the diffraction pattern of a sample of 70 mol % ErS consist of a mixture of ErAsS2 and ErS diffraction lines.
It has been established that the compound ErAsS2crystallizes in the tetragonal syngony with unit cell parameters: a=13.62; c=18.93 Â;
3 3
Ppuc. = 5.17 g/cm , px-ray = 5.21 g/cm . X-ray data of the ErAsS2 compound are given in Table 1.
Some physicochemical parameters of alloys of the AsS-ErS system after annealing are given in Tabl. 2. When determining the micro-
hardness and density before and after annealing, two and three series of values were obtained. The data obtained show that the values of the microhardness of glasses are higher than the microhardness of the corresponding crystals. The density value for glasses, on the contrary, is less than that of the same crystals (Table 2).
As a result of complex physicochemical studies, a phase diagram of the AsS-ErS system was constructed (Figure 2). It has been established that the phase diagram of the AsS-ErS system is a quasi-binary section of the Er-As-S ternary system and belongs to the eutectic type. The coordinates of the resulting eutectic in the system are 10 mol % ErS and 280°C. In the AsS-ErS system, the ErAsS2 compound is formed in a ratio of 1:1. In the concentration range 0-10 mol % ErS, primary crystals of AsS-based a-solid solutions precipitate from the liquid. Within 10-25 mol % ErS crystals of ErAsS2 are precipitated from the liquid, and in the range of 25-100 mol % ErS crystals of ErS are precipitated from the liquid. Below the solidus line, two-phase alloys (a + ErAsS2) and (ErAsS2 + ErS) crystallize.
Table 1. Interplanar distances (d), intensities (I), and lattice indices (hkl) of the ErAsS2 X-ray diffraction patterns
No I, % dexp. Â dcal.. Â h k l
1 21 6.8105 6.8105 2 0 0
2 26 6.3213 6.3245 0 0 3
3 46 5.7319 5.7260 1 0 3
4 25 5.2765 5.2778 1 1 3
5 48 5.1100 5.1233 2 1 2
6 23 4.8679 4.8168 2 2 0
7 32 4.6194 4.6676 2 2 1
8 24 4.1828 4.1996 3 1 1
9 22 3.8950 3.9193 3 1 2
10 70 3.7543 3.7796 3 2 0
11 30 3.6971 3.7062 3 2 1
12 27 3.6617 3.6490 1 0 5
13 38 3.5752 3.5578 3 1 3
14 47 3.5343 3.5245 1 1 5
15 34 3.5017 3.5093 3 2 2
16 30 3.3761 3.3768 2 2 4
17 48 3.3290 3.3520 4 0 1
18 73 3.2729 3.2547 4 1 1
19 26 3.2025 3.2042 4 0 2
20 52 3.1129 3.1189 4 1 2
21 27 3.0421 3.0457 4 2 0
22 47 3.0160 2.9974 4 0 3
23 100 2.9171 2.9273 4 1 3
24 40 2.8727 2.8630 2 0 6
25 33 2.6548 2.6528 1 0 7
26 51 2.5685 2.5709 5 1 2
27 20 2.4839 2.4899 4 1 5
28 52 2.4405 2.4434 5 2 2
29 38 2.3101 2.3150 4 0 6
30 60 2.2393 2.2393 6 1 0
31 20 2.1822 2.1739 6 1 2
32 20 2.0716 2.0752 5 4 2
33 61 2.0248 2.0303 6 3 0
34 34 1.9946 1.9881 5 3 5
35 22 1.9488 1.9459 7 0 0
36 23 1.9247 1.9263 7 1 0
37 24 1.9069 1.9087 3 0 9
38 37 1.8816 1.8888 6 4 0
39 34 1.8138 1.8095 6 4 3
40 26 1.7589 1.7571 7 3 2
41 22 1.7338 1.7308 4 2 9
42 23 1.7089 1.7085 1 0 11
43 28 1.6364 1.6364 6 5 4
44 29 1.6319 1.6319 8 1 3
45 19 1.5923 1.5911 8 1 4
46 24 1.5814 1.5833 7 5 0
Table 2. Composition, results of DTA, measurements of microhardness and determination of the density of alloys of the AsS-ErS system after annealing (crystalline)_
Composition, mol % Thermal effects, 0С Density, 103 kg/m3 Microhardness, MPa
AsS ErS a ErAsS2 ErS
Р=0.1 H P=0.2 Н
100 0.0 315 3.52 660 - -
97 3.0 310 3.57 770 - -
95 5.0 280,305 3.68 810 - -
90 10 280 3.84 Eutect. Eutect. -
85 15 280,400 3.99 - - -
80 20 280,500 4.17 - - -
70 30 280,745 4.48 - 2000 -
60 40 750,950 4.81 - 2000 -
50 50 750,1190 5.17 - 2100 -
40 60 750 5.46 - 2300
30 70 750 5.78 - 2300
20 80 750 6.30 - -
10 90 750 6.42 - -
0.0 100 2180 6.75 - -
Conclusion
The interaction of AsS and ErS compounds was studied by the methods of physico-chemical analysis and the T-x phase diagram of AsS-ErS was constructed. It was found that the phase diagram of the system is quasi-binary, eutectic and characterized by the formation of the chemical compound ErAsS2. The ErAsS2 compound is formed by the peritectic reaction with L + ErS~ ErAsS2 at 7500C. AsS and ErS compounds form a eutectic, with coordinates of 10 mol % ErS and 2800C. In the system, the region of glass formation based on AsS reaches 10 mol % ErS. For alloys from the area of glass, some physical and chemical properties have been studied. Solubility based on AsS reaches up to 1.5 mol % ErS, and based on ErS, the solubility is practically not established. As a result of X-ray diffraction analysis, it was found that the ErAsS2 compound crystallizes in a tetragonal syngony with lattice parameters: a=13.62;
3 3
c=18.93; Ppuc.= 5.17 g/sm , px-ray = 5.21 g/sm .
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AsS-ErS SÍSTEMÍNDO FAZA TARAZLIGI VO SÜ^aaMOLaGOLMa
T.M.ilyasli, D.T.Hasanova, LLOliyev
AsS va ErS birlaçmalari arasinda faza tarazligi va çûçaamalagalma fiziki-kimyavi analiz metodlan: diferensial-termiki (DTA), rentgenfaza (RFA), mikroquruluç (MQA), hamçinin mikrobarkliyin va sixligin olçqlmasi ila tadqiq edilmiçdir va AsS-ErS sisteminin T-x faza diaqrami qurulmuçdur. Müayyan edilmiçdir ki, sistemin faza diaqrami kvazibinar olub, evtektik tiplidir. Sistemin hal diaqrami ErAsS2 kimyavi birlaçmasinin amala galmasi ila xarakteriza olunur. ErAsS2 birlaçmasi 7500C-da M + ErS^ ErAsS2 peritektik reaksiya naticasinda amala galir, tetraqonal sinqoniyada kristallaçir, qafas parametrlari: а=13.62; c=18.93 A; Ppik.= 5,17 g/sm3, prent = 5.21 g/sm3. AsS va ErS birlaçmalari arasinda amala galan evtektikanrn tarkibi 10 mol % ErS, temperatura 2800C. Normal soyutma çaraitinda AsS birlaçmasi asasinda çûçaamalagalma sahasi 10 mol % ErS-a çatir. §ü¡?a sahasinda olan arintilar ûçûn müayyan fiziki-kimyavi xassalar tadqiq edilmiçdir. AsS asasinda hallolma 1.5 mol % ErS va ErS asasinda isa hallolma praktiki olaraq müayyan edilmamiçdir.
Açar sozlar: faza, §щээшэ^э1шэ, mikrobarklik, likvidus, sinqoniya.
ФАЗОВОЕ РАВНОВЕСИЕ И СТЕКЛООБРАЗОВАНМ В СИСТЕМЕ AsS-ErS
Т.М.Ильяслы, Д.Т.Гасанова, И.И.Алиев
Фазовое равновесие и стеклообразование между соединениями AsS и ErS изучено методами физико-химического анализа: дифференциально-термического (ДТА), рентгенофазового (РФА), микроструктурного (MCA), а также путем измерения микротвердости и плотности, была построена T-х фазовая диаграмма системы AsS-ErS. Установлено, что фазовая диаграмма системы квазибинарная, эвтектического типа и характеризуется образованием химического соединения ErAsS2. Соединение ErAsS2 образуется по перитектической реакции Ж+ErS-^- ErAsS2 при 7500C, кристаллизуется в тетрагональной сингонии с параметрами решетки: а=13.62; с=18.93 A; рпик.= 5.17 г/см3, ррент= 5.21 г/см3. Состав эвтектики между соединениями AsS и ErS составляет 10 мол. % ErS и температура 280oC. При нормальных условиях охлаждения область стеклообразования на основе AsS достигает 10 мол. % ErS. Для сплавов из стекольной области изучены некоторые физико-химические свойства. Растворимость на основе AsS достигает до 1.5 мол. % ErS, а на основе ErS растворимость практически не установлена.
Ключевые слова: фаза, стеклообразование, микротвердость, ликвидус, сингония.
