INVESTIGATION OF CHEMICAL INTERACTIONS IN THE As2Te3-TlGaTe2 SYSTEM

Danish Scientific Journal No101, 2025 15 INVESTIGATION OF CHEMICAL INTERACTIONS IN THE As2Te3-TlGaTe2 SYSTEM Ahmedova C. Doctor of Chemical Sciences, Professor, Adiyaman University, Faculty of Arts and Sciences, Department of Chemistry, Turkiye https://doi.org/10.5281/zenodo.17493454 Abstract Chemical interactions in the As2Te3-TlGaTe2 system were studied using differential thermal analysis (DTA), X-ray diffraction (XRD), microstructural analysis (MSA), as well as density and microhardness measurements. A T-x phase diagram was constructed. The phase diagram of the system is quasi-binary and eutectic. The composition of the eutectic formed by the As2Te3 and TlGaTe2 compounds is 25 mol. % TlGaTe2, and the temperature is 265°C. Based on the results of microstructural analysis, it was established that a solid solution region with a concentration of 5 mol. % TlGaTe2 is formed in the system based on the As2Te3 compound, while the solubility based on TlGaTe2 is 10 mol. % As2Te3. The physico-chemical properties of alloys of the As2Te3-TlGaTe2 system depending on the composition were studied. Keywords: phase, solid solution, quasi-binary, eutectic, density. Introduction Arsenic chalcogenides, as well as new phases and solid solutions based on them, are materials with photovoltaic [1–6], luminescent [7,8], and acousto-optic [9–12] properties. Arsenic sulfide and selenide compounds are usually obtained as glasses, while telluride compounds are crystalline substances. Recently, semiconductor glass fibers based on arsenic chalcogenides have attracted the attention of researchers as materials with unique properties [13–16]. The As2Te3 compound and new phases based on it exhibit high photovoltaic properties [17–20]. A large number of materials with photovoltaic properties have also been obtained based on the TlGaTe2 compound [20–23]. The TlGaTe2 compound has superionic conductivity [24–25]. From this perspective, studying chemical interactions with TlGaTe2 has both scientific and practical significance. We have studied a number of systems involving the compound As2Te3. The As2Te3–TlGaTe2 system is studied for the first time. The aim of this work is to study the chemical interaction in the As2Te3-TlGaTe2 system, construct its phase diagram, and investigate the X-ray diffraction analysis and physicochemical properties of the obtained phases. The As2Te3 compound melts congruently at 381°C and crystallizes in the monoclinic syngony with the lattice parameters: a = 14.339 Ǻ; b = 4.006 Ǻ; c = 9.873 Ǻ, β = 95°, sp. gr. C2/m [26]. The TlGaTe2 compound melts congruently at 775°C and crystallizes in the tetragonal syngony with the unit cell parameters: a = 8.22; c=7.10 Ǻ, z=4, density and microhardness ρ=7.32 g/cm3 and 900 MPa, respectively [27]. Experimental Section High-purity elements were used to synthesize the components of the As2Te3-TlGaTe2 system (As2Te3 and TlGaTe2): As – 99.99%, Tl – 99.98%, Ga – 99.999%, and single-crystal Te – 99.999%. The As2Te3-TlGaTe2 alloys were then prepared by co-melting the As2Te3 and TlGaTe2 components in a quartz ampoule with air evacuated to a pressure of 0.133 Pa. The alloys were synthesized in the temperature range of 600–900°C. To homogenize the alloys, heat treatment was performed at 265°C for 240 hours. The samples were analyzed at equilibrium using physicochemical analysis methods (DTA, X-ray fluorescence, microcavitation, density, and microhardness measurements). Differential-thermal analysis (DTA) was performed using a THERMOSCAN-2 pyrometer. A chromel-alumel thermocouple was used, and the heating rate was 5°C/min. Рентгеноструктурный анализ (РФА) проводили на рентгеновском дифрактометре D2 PHASER с использованием CuKα-излучения и Ni-фильтра. Микроструктурный анализ образцов проводили на микроскопе МИМ-8. Для разделения фаз в хорошо полированных образцах в качестве травильного раствора использовали хромовый раствор. Микротвердость сплавов измеряли на металлографическом микроскопе ПМТ-3. Плотность образцов определяли пикнометрическим методом, в качестве рабочего раствора использовали толуол. Results and Discussion To study the chemical interactions in the As2Te3TlGaTe2 system, alloys of this system were synthesized. The behavior of the resulting alloys in various environments was studied. They were found to be stable in air and organic solvents. Strong acids (HNO3, HCl) and alkalis (NaOH, KOH) decompose them. To study the phase composition of the system, the microstructure of the samples was examined. Figures 1, a, b, c, and d, show the microstructures of As2Te3-TlGaTe2 samples with contents of 5, 25, 60, and 90 mol. %. TlGaTe2. CHEMICAL SCIENCES 16 Danish Scientific Journal No101, 2025 Fig. 1. Microstructures of alloys in the As2Te3-TlGaTe2 system. 1-5, 2-25, 3-60, 4-90 mol.% TlGaTe2. In Fig. 1, the single-phase sample of 5 mol. % TlGaTe2, the As2Te3 compound, is predominantly a solid solution. The 25 mol. % TlGaTe2 sample is a eutectic composition formed in the system. The 60 mol. % TlGaTe2 sample is a two-phase alloy. The 90 mol. % TlGaTe2 sample is a solid solution based on the TlGaTe2 compound. Fig. 2. Diffraction patterns of alloys in the As2Te3-TlGaTe2 system. 1 - As2Te3, 2 - 5, 3 - 60, 4 - 90, 5 - 100 mol. % TlGaTe2. To confirm the results of differential thermal and microstructural analysis, X-ray diffraction patterns of alloys containing 5, 60, and 90 mol. % TlGaTe2 were obtained (Fig. 2). It was found that the diffraction lines present in the diffraction patterns of single-phase alloys containing 5 and 90 mol. % TlGaTe2 are identical to those of As2Te3 and TlGaTe2 compounds, respectively. That is, these samples are solid solution alloys based on As2Te3 and TlGaTe2 compounds. The diffraction lines of the 60 mol. % alloy % TlGaTe2 are a mixture of diffraction lines from the original components. Thus, Xray diffraction analysis confirms the results of DTA and MSA. Based on the results of physicochemical analysis, a T-x phase diagram of the As2Te3-TlGaTe2 system was constructed (Fig. 3). As can be seen from Fig. 3, the phase diagram of the system is eutectic. Solid solution regions formed in a limited area based on the original components. In the As2Te3-based system, a TlGaTe2 solid solution with a concentration of 5 mol. % formed. The area of the solid solution based on the TlGaTe2 compound is 10 mol % TlGaTe2. a) b) c) d) Danish Scientific Journal No101, 2025 17 Fig. 3. T-x phase diagram of the As2Te3-TlGaTe2 system. The results of microhardness measurements of the As2Te3-TlGaTe2 system alloys show that two different microhardness values were determined. The compositional dependence of some physicochemical properties of the system's alloys is presented in Table 1. As can be seen from the table, the microhardness value (1600–1670) MPa corresponds to the microhardness of the α-solid solution formed on the As2Te3 compound, while the value (900–80) MPa corresponds to the microhardness of the β-solid solution formed on the TlGaTe2 compound. The dependence of the alloy density on composition is linear and consistent. The liquidus of the As2Te3-TlGaTe2 system is formed by the monovariant equilibrium curves of the α and β solid solutions. In this system, two-phase alloys consisting of (α + β) crystallize below the solidus line in the concentration range of 5–90 mol. % SrInSe2. The coordinate of the eutectic formed in the system is 25 mol. % TlGaTe2, and the temperature is 265°C. Table 1. Composition, differential thermal analysis data, microhardness, and densities of alloys in the As2Te3-TlGaTe2 system Composition , mol. % Thermal effects, oC Density, g/cm3 Microhardness , MPa As2Te3 TlGaTe2 α β Р=0,15 N Р=0,10 N 100 0,0 381 5,40 1600 - 97 3,0 330,380 5,44 1630 - 95 5,0 315,370 5,48 1650 - 90 10 265,350 5,59 1650 - 85 15 265,340 5,69 1650 - 80 20 265,300 5,78 - - 75 25 265 5,88 Eutec. Eutec. 70 30 265,410 5,98 - - 60 40 265,570 6,17 - 980 50 50 265,640 6,36 - 980 40 60 265,680 6,55 - 980 30 70 265,710 6,74 - 980 20 80 265,735 6,94 - 980 10 90 420,760 7,13 - 980 5,0 95 570,770 7,22 - 960 0,0 100 775 7,32 - 900 Conclusion The chemical interaction in the As2Te3-TlGaTe2 system was studied using differential thermal analysis (DTA), X-ray diffraction (XRD), microstructure analysis (MSA), and density and microhardness measurements. A T-x phase diagram was constructed. The phase diagram of the system is quasi-binary and eutectic. Co-crystallization of As2Te3 and TlGaTe2 compounds is completed at the binary eutectic point. The 18 Danish Scientific Journal No101, 2025 eutectic composition is 25 mol. % TlGaTe2, and the temperature is 265°C. In the system at room temperature, a solid solution region with a concentration of 5 mol. % TlGaTe2 formed based on the As2Te3 compound, and a solid solution region with a concentration of 10 mol. % As2Te3 formed based on the TlGaTe2 compound. The dependence of the density and microhardness of alloys of the As2Te3-TlGaTe2 system on the composition was studied. References: 1. Dinesh Chandra SATI1, Rajendra KUMAR, Ram Mohan MEHRA Influence of Thickness Oil Optical Properties of a: As2Se3 Thin Films // Turk J Phys. 2006. V.30. P. 519527. 2. Lovu M., Shutov S., Rebeja S., Colomeyco E., Popescu M. Effect of metal additives on photodarkening kinetics in amorphous As2Se3 films // Journal of Optoelectronics and Advanced Materials 2000. V. 2. Issue: 1. P 53-58. 3. 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