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ISSN 2522-1841 (Online) AZERBAIJAN CHEMICAL JOURNAL № 1 2021 ISSN 0005-2531 (Print)
UDC 546. 56.24-19.24
RESEARCH CHEMICAL INTERACTIONS IN THE CuTe-As2Te3 SYSTEM
LLAliev1, S.Sh.Ismailova1, M.H.Shakhbazov2
M.Nagiyev Institute of Catalysis and Inorganic Chemistry, NAS of Azerbaijan 1 Azerbaijan State Pedagogical University2.
aliyevimir@rambler.ru
Received 04.11.2020 Accepted 09.12.2020
By the methods of DTA, XRD, MSA, as well as by measuring the microhardness and determining the density of the alloys, the CuTe-As2Te3 system was studied and a phase diagram was constructed. The system state diagram is of the eutectic type and it is characterized by one chemical compound of Cu3As4Te9 composition. Compounds Cu3As4Te9 melts incongruently at 3200C. Solid solutions based on As2Te3 reaches 8 mol %, and based on CuTe solid solutions are practically not installed. Cu3As4Te9 and As2Te3 form an eutectic composition of 45 mol % As2Te3 and temperature 2650C. The results of X-ray phase analysis have shown that the Cu3As4Te9 compounds is crystallized in the tetragonal syngony with lattice parameters: a = 13.86, c = 18.05 A, Z = 9, ppyk. = 6.96 g/cm3, prent. = 7.06 g/cm3.
Keywords: eutectic, incongruent, microhardness, density, syngony.
doi.org/10.32737/0005-2531-2021-1-67-71
Introduction
This study relates to the field of synthesis of semiconductor compounds and solid solutions with technically important properties. It is known that among the materials used in optoelectronics, photodetectors, photoresistors, lasers and phosphors, an important place is occupied by compounds and solid solutions based on arsenic chalcogenides [1-8]. Copper chalcogeni-des and alloys based on them as thermoelec-tronic and superionic materials are widely used in radio- and electronic engineering [9-14]. Some quasi-binary sections with the participation of arsenic chalcogenides and the Cu-As-Se (Te) ternary system have been investigated in the literature [15-17]. However, there is no data in the literature on interactions in the CuTe-As2Te3 system.
The aim of this work is to synthesize and study the interaction in the CuTe-As2Te3 system and build a phase diagram, as well as search for new semiconductor phases and solid solutions.
The CuTe compound melts incongruently at 3670C and crystallizes in a rhombic syngony with unit cell parameters: a = 3.16, b = 4.07, c = 6.92 Â, sp. gr. Pmmm-D 13 [18]. According to [19], the CuTe compound melts incongruently
at 4000C. The As2Te3 compound melts with an open maximum at 3810C and crystallizes in monoclinic syngony with lattice parameters: a = 14.339, b = 4.006, c = 9.873 A, p = 950, sp.gr. C2/m, the density is p = 6.25 g/cm3 [20].
Experimental part
The synthesis of the initial components of the system was carried out from the elements Cu-99.97, tellurium Te-99.998 and arsenic 99.99 taken in stoichiometric proportions. Triple alloys of the CuTe-As2Te3 system were synthesized in a one temperature furnace by the ampoule method from the CuTe and As2Te3 components. Taking into account the peritectic nature of the formation of the CuTe compound, annealing was performed for 350 h at a temperature of ~200C below the final crystallization temperature.
The study of the CuTe-As2Te3 ternary system was carried out by methods of physico-chemical analysis: differential thermal (DTA), X-ray phase (XRD), microstructural (MSA), as well as density determination and microhard-ness measurement.
Thermograms were recorded on an NTR-73 low-frequency instrument, with a heating rate of 9 deg/min. Diffraction patterns were recorded on a D-2 PHASER setup. Microhardness was
measured on a PMT-3 microhardness meter at loads selected as a result of studying the micro-hardness of each phase. The microstructure of the alloys was studied using a MIM-8 microscope. The alloys of the CuTe-As2Te3 system were etched with a mixture of 1N HNO3: H2O2=1:1. The density was determined by the pycnometric method; toluene was used as the working fluid.
Results and its discussion
Synthesized alloys of the CuTe-As2Te3 system are compact gray in color. Alloys of the system, water resistant and organic solvents. Well soluble in acids HNO3 and H2SO4. Alloys rich in As2Te3 also dissolve in alkalis (NaOH, KOH).
The DTA of the CuTe-As2Te3 system showed that two and three endothermic effects related to solidus and liquidus are observed on the thermograms of the alloys.
The results of microstructural analysis show that all alloys of the CuTe-As2Te3 system are two-phase. Only on the basis of As2Te3 is there an insignificant region of solid solutions, while on the basis of CuTe solid solutions are practically not detected. This indicates that the CuTe-As2Te3 section is a quasi-binary, eutectic type.
To confirm the results of DTA and MSA analyzes, an X-ray phase analysis of alloys of the system 30, 60 mol % As2Te3. It was estab-
lished that the diffraction patterns of alloys with marked compositions, in addition to composition 60 and 92-100 mol % other alloys consist of mixed diffraction lines of the starting components. The content of 60 mol% As2Te3 corresponds to the formula Cu3As4Te9. Figure 1 presents the diffraction patterns of the Cu3As4Te9 compound and the initial components. The data obtained indicate that in the CuTe-As2Te3 system contains one- and two-phase alloys.
The phase diagram of the CuTe-As2Te3 system constructed by the totality of the data from the above analysis methods is shown in Figure 2. The state diagram of the system is quasi-binary, eutectic type, characterized by the presence of one chemical compound of the composition Cu3As4Te9. This compound melts with an open maximum at 3200C. Cu3As4Te9 and As2Te3 form between themselves an eutec-tic composition of 45 mol % As2Te3 and temperature 2650C (Table 1).
The results of X-ray phase analysis have shown that the Cu3As4Te9 compounds crystallizes in the tetragonal syngony with lattice parameters: a=13.86, c=18.05 Â, Z = 9, ppyk=6.96 g/cm3, prent. = 7.06 g/cm3.
The results of X-ray diffraction data for the compound Cu3As4Te9 are shown in Table 2.
As2Te3
I, % 1000 "i
800 H
600
400 -
200
S sis 3323 g 2 § 3
29
Fig.1. Diffractograms of alloys of Cu3As4Te9: system 1 - CuTe, 2 - 60 (Cu3As4Te9), 3 - As2Te3.
RESEARCH CHEMICAL INTERACTIONS IN THE CuTe-As2Te-
69
t0,C 700
630° 600
500
400
300
200 100
CuTe
381°
20
40
60 mol %
80
As2Te3
Fig. 2. Phase diagram of the CuTe-As2Te3 system.
Table 1. The results of DTA. measurements of microhardness and density of alloys of the CuTe-As2Te3 system
Composition, mol % Thermal effects, °C Density, g/cm3 Microhardness of phases, MPa
CuTe Cu3As4Te9 ß
CuTe As2Te3
P=0.10 H P=0.15H
100 0.0 400,630 6.94 400 - -
95 5.0 250,385,615 6.92 490 - -
90 10 250,375,575 6.90 520 - -
80 20 250,305,450 6.92 530 - -
75 25 250,375 6.92 530 1980 -
70 30 250,300 6.92 530 1980 -
65 35 250,310 6.94 - 1970 -
60 40 320 6.96 - 1960 -
55 45 265 6.93 Eutec. Eutec. -
50 50 265,300 6.90 - - -
40 60 265,335 6.80 - - 1850
30 70 265,345 6.74 - - 1850
20 80 265,360 6.60 - - 1850
10 90 300,370 6.45 - - 1850
5.0 95 330,375 6.35 - - 1850
3.0 97 345,380 6.28 - - 1800
0.0 100 381 6.25 - - 1650
Table 2. Intcrplanar spacings d lattice indices (hkl) and intensities (I) of Cu3As4Te9 compound
I, % d, À hkl I, % d , À hkl
21 6.9317 200 7 2.0713 630
4 5.5384 103 23 2.0208 337
22 3.5182 323 14 1.9783 700
16 3.4708 400 4 1.7610 546
23 3.2639 330 7 1.7339 800
100 3.0082 006 9 1.66932 31.10
42 2.8713 116 7 1.6315 10.11
9 2.6454 502 3 1.5802 33.10
12 2.5337 107 3 1.5150 609
28 2.3221 600 5 1.5036 00.12
10 2.2623 008 2 1.4382 22.12
1 2.1841 620
Liquidus systems are limited by primary crystallization, by monovariant curves of Cu4Te3 and a-phase solid solutions based on Cu3As4Te9. The CuTe compound melts incongruently at 4000C, above the peritectic temperature it decomposes according to the following reactions: CuTe^L + Cu4Te3. In the concentration range of 0-25 mol % As2Te3 primary Cu4Te3 crystals are released from the liquid. Upon recrystalliza-tion below the curves, a three-phase region forms (L+Cu4Te3+ Cu3As4Te9).
In the concentration range of 0-40 mol % As2Te3 below the solidus line, two-phase CuTe+Cu3As4Te9 alloys crystallize, and in the range of 40-92 mol % As2Te3 crystallizes (Cu3As4Te9+a). In the system in the solid state, solid solutions based on As2Te3 are 8 mol. %, and based on CuTe solid solutions are practically not installed.
Some physicochemical properties of the alloys of the CuTe-As2Te3 system are given in Table 1. At measuring the microhardness of the alloys of the system. different microhardness values were established. The microhardness value for the CuTe compound varies in the range of (400-530) MPa. The microhardness value (19601980) MPa corresponds to the microhardness of the Cu3As4Te9 compound. The microhardness values for the a-solid solution obtained on the basis of As2Te3 vary from 1650 to 1850 MPa.
Conclusion
The interactions between CuTe and As2Te3 are investigated in a wide concentration range and the T-x phase diagram of the system is constructed. It has been established that the
CuTe-As2Te3 system belongs to the eutectic type. One chemical compound Cu3As4Te9 is formed in the system. It was found that Cu3As4Te9 compounds melt congruently at 3200C. In the system at room temperature, solid solutions based on As2Te3 reach 8 mol % CuTe. while solid solutions based on CuTe have practically not been established. CuTe and As2Te3 form a eutectic with coordinates 45 mol % As2Te3, temperature 2650C. According to the results of X-ray phase analysis. it was found that the compound Cu3As4Te9 crystallizes in the tetragonal sysngony, with the lattice parameters: a = 13.86, c = 18.05 A. Z=9, Ppyk. = 6.96 g/cm3, prent =7.06 g/cm3.
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CuTe-As2Te3 SÍSTEMÍNDO KÍMYOVÍ QAR§ILIQLI TOSÍRÍN TODQÍQÍ
LLOliyev, S.§.ïsmayilova, M.H.§ahbazov
Fiziki-kimyavi analiz (DTA, MCA, RFA, elaca da mikrobarkliyin va xüsusi çakinin tayini) metodlari vasitasila CuTe-As2Te3 sisteminda qarçiliqli tasir tadqiq edilmiç va faza diaqrami qurulmuçdur. Sistem 3200C temperaturda konqruyent ariyan Cu3As4Teo tarkibli birlaçmasinin amala galmasi ila xarakteriza olunur. As2Te3 asasinda otaq temperaturunda 8 mol % CuTe bark mahlul sahasi amala galdiyi halda, CuTe birlaçmasi asasinda bark mahlul sahasi praktik olaraq tayin edilmamiçdir. Cu3As4Teo va As2Te3 öz aralarinda evtektika amala gatirir, tarkibi 45 mol % CuTe, temperaturu 2650C-dir. Rentgenfaza analizinin naticalarina asasan müayyan edilmiçdir ki, Cu3As4Teo birlaçmasi tetraqonal sinqoniyada kristallaçir, qafas parametrlari: a = 13.8б, c = 18.05 Â. Z = 9, ppik = б.Об g/cm3, prent = 7.0б g/cm3-dir.
Açar sözlzr: evtektika, inkonqruyent, mikrobarklik, sixliq, sinqoniya.
ИССЛЕДОВАНИЕ ХИМИЧЕСКИЕ ВЗИМОДЕИСТВИЯ В СИСТЕМЕ CuTe-As2Te3
И.И.Алиев, С.Ш.Исмаилова, М.Г.Шахбазов
Методами ДТА, РФА, МСА а также путем измерения микротвердости и определения плотности сплавов исследованы в системе CuTe-As2Te3 и построена фазовая диаграмма. Система характеризуется образованием соединения состава Cu3As4Te9, которое плавится конгруэнтно при 3200С. На основе As2Te3 образуются 8 мол % твердых растворов, а на основе CuTe твердые растворы практически не установлены. Cu3As4Te9 и As2Te3 между собой образуют эвтектику при составе 45 мол% As2Te3 и температуре 2650С. По результатам рентгенофазового анализа установлено, что соединение Cu3As4Te9 кристаллизуется в тетрагональной сингонии с параметрами решетки: a =13.86, c = 18.05 A. Z=9, рпик=6.96 г/см3, р^н^.Об г/см3.
Ключевые слова: эвтектика. инконгруэнтный. микротвердость. плотность. сингония.
