CC BY
19
ISSN 2522-1841 (Online) ISSN 0005-2531 (Print)
UDC 544.344.015.3: 546.5722/24
PHASE RELATIONS IN THE Ag8SiS6-Ag8SiTe6 SYSTEM AND CHARACTERIZATION OF SOLID SOLUTIONS
12 2 11 A.J.Amiraslanova , K.N.Babanly , S.Z.Imamaliyeva , I.J.Alverdiyev , Yu.A.Yusibov
1Ganja State University, Ganja, Azerbaijan 2M.Nagiyev Institute of Catalysis and Inorganic Chemistry, Ministry of Science and Education
of the Republic of Azerbaijan
Received 07.12.2022 Accepted 01.02.2023
Argyrodite family compounds and phases based on them are valuable ecologically friendly functional materials that exhibit a number of functional propreties, such as thermoelectric, photoelectric, optical, and other. On the other hand, having Cu+ and Ag+ ion conductivity, they are ionic conductors, and can be used as electrochemical sensors, electrodes, or electrolyte materials in solid-state batteries, displays, etc. In the present paper, phase relations in the Ag8SiS6-Ag8SiTe6 system were studied by differential thermal analysis and X-ray diffraction phase techniques and a T-x phase diagram was constructed. It is established that the system is quasi-binary and is characterized by the formation of a continuous series of substitutional solid solutions between Ag8SiTe6 and HT- Ag8SiS6 compounds. With the formation of solid solutions, the temperature of the polymorphic transition of the Ag8SiS6 decreases. This leads to the stabilization of the ion-conducting cubic phase in the range of compositions >30 mol. % Ag8SiTe6 at room temperature and below. The homogeneity regions based on RT-Ag8SiS6 are 10 mol. %. According to XRD data, the crystal lattice parameters of the obtained solid solutions were calculated and a their linear dependence on the composition is shown.
Keywords: silver-silicon sulfide, silver-silicon telluride, argyrodite-like compounds, differential thermal analysis, X-ray diffraction analysis, phase equilibria, solid solutions, polymorphic transformation.
doi.org/10.32737/0005-2531-2023-2-169-177
Introduction
Complex chalcogenides of silver and copper with heavy elements attract the attention of researchers as ecologically friendly functional materials with several properties, such as thermoelectric, photoelectric, optical, and other properties [1-9]. Among these materials, an important place is occupied by compounds of the argyrodite family with the general formula AI8BivX6 (A-Cu, Ag; BIV-Si, Ge, Sn; X-S, Se, Te) and phases based on them [10-19] which, in addition to these properties, also have ionic conductivity for Cu+ and Ag+ cations and can be used as solid electrolytes in solid-state batteries, as well as electrochemical sensors and electrodes [20-26]. According to [24-26], the presence of mixed electronic-ionic conductivity is one of the significant factors that positively affect the thermoelectric characteristics of these materials.
For the development of directed methods for the synthesis of new materials, it is very useful to understand the phase relationships in the corresponding systems [27-29]. Systems characterized by the formation of solid solutions are of particular interest because the properties of the material can be changed by varying the composition [30-33]. The constructed phase diagrams of such systems serve as the basis for choosing the composition of melts for growing single crystals of solid solutions of a given composition by the method of directed crystallization.
Previously [34-40], the results of studies of systems characterized by the formation of wide regions of solid solutions were presented.
The purpose of this work is the investigation of the phase relations in the Ag8SiS6-Ag8SiTe6 system, obtaining and characterizing new phases of variable composition.
The Ag8SiS6 melts congruently [41-45]. However, in these works, melting temperatures are given that differ greatly from each other: 1213 K [41], 1223 K [42], 1232 K [43], 1243 K [44], and 1231 [45]. The polymorphic transition temperatures are also different: 507 K [41, 42], 510 K [44], and 526 K [45]. High-temperature (HT)-modification of this compound crystallizes in cubic structure (Sp.Gr. F-43m, a=1.063 nm [41]), and the room temperature (RT)-modification has an orthorhombic crystal structure (Sp.gr. Pna21, a=1.5024, ¿=0.7428, c=1.0533 nm [46]; a=1.5043, b=0.7452, c=1.0565 [47]).
The Ag8SiTe6 melts congruently at 1143 K [41] and crystallizes in cubic structure (Sp.Gr. F-43m, a = 1.15225 nm [48]). According to [48], this compound also has two polymorphic transformations at 195 and 263 K.
As can be seen from the literature data, it can be assumed that the HT- Ag8SiS6 and Ag8SiTe6 can form continuous series of solid solutions. On the other hand, the character of the interaction of RT-Ag8SiS6 compound with Ag8SiTe6 should be different.
Materials and methods
The initial Ag8SiS6 and Ag8SiTe6 compounds were synthesized from high-purity elements (at least 99.999 wt. % purity). The stoichiometric compositions of elements were placed into quartz ampoules (15 cm in length and 1.5 cm in diameter), evacuated to ~10 2 Pa, and fused. To avoid a reaction between silicon and the quartz ampoule, a thin layer of carbon was deposited by graphitizing on the inside of the quartz tube.
Synthesis of the Ag8SiTe6 compound was carried out in an inclined furnace at 1200 K.
The Ag8SiS6 compound was synthesized in an inclined two-zone furnace. The lower "hot zone" was slowly heated to 1270 K, and the cold zone to 670 K. The "hot zone" plays the role of the component interaction zone, and in the "cold zone" elemental sulfur vapor condens-
es and returns to the interaction zone. As a result of the ongoing reaction, in the "cold" part of the ampoule, the mass of elemental sulfur decreases and within 1-2 hours it is almost completely consumed. After that, the ampoule was completely transferred to the hot zone, kept at the indicated temperature for 1 -2 h, and cooled in the switched off furnace.
DTA and XRD analysis were employed for the identification of the synthesized compounds.
According to the DTA data (Fig.1), Ag8SiS6 and Ag8SiTe6 compounds melts at 1225 K and 1143 K. On the heating thermogram of the Ag8SiS6 compound, there is also an endo-thermic effect at 513 K, corresponding to the polymorphic transition. These data on the melting temperature and polymorphic transition are close to the results of [41, 42, 44].
Powder diffraction patterns of the synthesized compounds are presented in Figure 2 with indication of the corresponding literature data. As can be seen, the diffraction patterns of both compounds completely coincide with the diffraction reflexes presented in the database [49].
All peaks on powder diffractograms can be indexed as pure phases of Ag8SiS6 and Ag8SiTe6 compounds. The calculated parameters of crystal lattices are presented in the "Results and discussions" section (Table 1).
Samples of the studied Ag8SiS6-Ag8SiTe6 system were prepared by melting stoichiometric amounts of preliminarily synthesized compounds in evacuated and sealed quartz ampoules. The alloys were heated to 1250 K and kept at this temperature for about 1 hour, then the furnace temperature was reduced to 800 K and kept in it for about 500 hours. For some compositions, two series of alloys were prepared: the first series after annealing was slowly cooled in a furnace to room temperature, and the second series after annealing was quenched in cold water.
Fig. 1. DTA heating curves of the Ag8SiS6 and Ag8SiTe 6 compounds.
Fig. 2. Powder diffraction patterns of the synthesized Ag8SiS6 and Ag8SiTe6 compounds Samples were analyzed using DTA, XRD and SEM methods. XRD data were obtained at room temperature using a Bruker D8 ADVANCE diffrac-tometer (with Cu-Ka1 radiation). DTA of equilibrium alloys was carried out on a NETZSCH 404 Fl Pegasus system with a heating rate of 10 K/min. SEM-EDS analyses were done by Tescan Vega 3 SBH Scanning Electron Microscope equipped with Thermo Scientific Ultra Dry Compact EDS detector.
Diffraction Angle [°28]
Fig. 3. Powder diffractograms of some alloys of the Ag8SiS6-Ag8SiTe6 system slowly cooled after annealing.
Results and discussion
The XRD data of the alloys slowly cooled after annealing (Figure 3) showed that in the AgsSiS6-AgsSiTe6 system, the 10 mol.% Ag8SiTe6 alloy has a diffraction pattern identical to that of the RT- Ag8SiS6, while alloys with compositions >30 mol% Ag8SiTe6 have a cubic diffraction pattern that is qualitatively similar to pure Ag8SiTe6. The diffraction pattern of the 20 mol.% Ag8SiTe6, along with reflection lines of the cubic phase, also contains reflections characteristic of RT- Ag8SiS6.
The powder XRD patterns for initial compounds and solid solutions were indexed using Topas V3.0 software and lattice parameters were calculated (Table 1). The diffraction pattern of the 10 mol.% Ag8SiTe6 alloy is completely indexed in the RT-Ag8SiS6 orthorhom-bic lattice. The calculated parameters are somewhat higher than the corresponding values for pure RT- Ag8SiS6, which confirms the formation of solid solutions based on it. In slowly cooled alloys with compositions of >30 mol.%
Ag8SiTe6, as well as alloys quenched from 800 K, a linear dependence of the cubic lattice period on composition, is observed, i.e. they follow Vegard's rule (Figure 4). It should also be noted that the values of the lattice period of cubic phases at room temperature are somewhat smaller than those of alloys quenched from 800 K, which is due to the thermal expansion of the crystal lattice of the latter compared to room temperature.
Based on the DTA results (Table 2), the phase diagram of the Ag8SiS6-Ag8SiTe6 system was plotted (Figure 4). As can be seen, the system is quasi-binary and is characterized by the formation of a continuous series of solid solutions (5-phase) between HT- Ag8SiS6 and Ag8SiTe6. On the liquidus and solidus curves, the temperature changes monotonically between the melting points of the initial compounds. Based on RT- Ag8SiS6, a limited region (up to 10 mol.%) of solid solutions (y-phase) is formed. The formation of y- and 5-phases are accompanied by a decrease in the temperature
of the polymorphic transition of Ag8SiS6 (513 K), and the corresponding thermal effects are not observed on the DTA curves of alloys containing more than 20 mol.% Ag8SiTe6. This shows that in the specified ranges of compositions, the temperature of this transition occurs at temperatures below room temperature.
The character of solid-phase equilibria in the Ag8SiS6-Ag8SiTe6 system (Figure 5) was also confirmed by the SEM method. As examples, Figure 6 presents SEM patterns of an-
nealed and slowly cooled alloys with compositions of 20 and 30 mol% Ag8SiTe6. As can be seen, the alloy of composition 30 mol% Ag8SiTe6 (Figure 6a) is single-phase (ô-phase), and the alloy of composition 20 mol% Ag8SiTe6 (Figure 6b) is two-phase. In addition to the matrix ô-phase, it also contains the y-phase, which is formed as a result of the solid-phase decomposition of the ô-phase (Figure 5).
Composition, mol% Ag8SiTe6 Syngony, Sp.Gr., lattice parameters, nm
Room temperature Quenched from 800 K
0 (Ag8SiS6) Orthorhombic. (Pna21): a=1.5032(3), b=0.7430(2), c=1.0538(3) Cubik: (F43m): a=1.0635(3)
10 Orthorhombic. (Pna21): a=1.5146(4); b=0.749(3); c=1.0627(3) -"-, »=1.0733(3)
20 Two-phases: y+ô -"-, »=1.0824(4)
30 Cubik: (F43m): a=1.0906(3) -"-, »=1.0915(4)
40 -"-, a=1.0995(3) -"-, «=1.1002(3)
60 -"-, a=1.1162(4) -"-, »=1.1167(4)
80 -"-, a=1.1335(4) -"-, a=1.1344(3)
Ag8SiTe6 -"-, 0=1.1524(4) -"-, a=1.1528(3)
Fig. 4. Dependence of the period of the cubic lattice of solid solutions on the composition in the Ag8SiS6-Ag8SiTe6 system.
Fig. 5. Phase diagram of the Ag8SiS6-Ag8SiTe6 system.
Composition, mol% Ag8SiTe6 Thermal effects, K
0 (Ag8SiS6) 513; 1225
10 467;1218
20 378;1210-1220
30 1298-1213
40 1178-1210
50 1180-1200
60 1175-1190
80 1160-1173
100 1143
a) b)
Fig. 6. SEM images of the alloys with compositions of 30 and 20 mol% Ag8SiTe6.
Conclusion
In this paper, we present new data on phase equilibria in the Ag8SiS6-Ag8SiTe6 system obtained by DTA and SEM methods as well as PXRD technique. The T-x phase diagram of the system was constructed. It was shown that the system is quasibinary, belongs to the first type according to Roseboom, and is characterized by the formation of a continuous series of substitutional solid solutions between Ag8SiTe6 and HT-Ag8SiS6. The formation of solid solutions leads to a strong decrease in the temperature of the polymorphic transition of the Ag8SiS6. As a result, the ion-conducting cubic phase is stabilized in the range of compositions >30 mol.% Ag8SiTe6 at room temperature and below. The solubility based on the low-temperature rhombic modification of Ag8SiS6 is 10 mol.%. From the powder diffraction patterns data, the crystal lattice parameters of the identified solid solutions were calculated. It was shown that the dependence of the cubic lattice period on the composition satisfies Vegard's rule. The obtained new solid solutions are of interest as potential environmentally friendly materials with thermoelectric properties and mixed ion-electronic conductivity.
Acknowledgments
The work has been partially supported by the Science Development Foundation under the President of the Republic of Azerbaijan, Grant No EIF-BGM-4-RFTF-1/2017-21/11/4-M-12.
References
1. Ahluwalia G.K. Applications of Chalcogenides: S, Se, and Te. Springer-Verlag. New York, 2016.
2. Woodrow P. Chalcogenides: Advances in Research and Applications. Nova Science Pub Inc., 2018.
3. Liu X., Lee S., Furdyna J.K., Luo T., Zhang Y-H. Chalcogenide. From 3D to 2D and Beyond. Elsevier Science, 2019.
4. Scheer R., Schock H.-W. Chalcogenide Photo-voltaics: Physics, Technologies, and Thin Film Devices. Wiley-VCH, 2011.
5. Alonso-Vante N. Chalcogenide Materials for Energy Conversion: Pathways to Oxygen and Hydrogen Reactions. Springer, 2018.
6. Babanly M.B., Yusibov Yu.A., Abishev V.T. Ternary chalcogenides on the base of copper and silver. Baku: BGU [In Russian], 1993.
7. Kumar M., Meena B., Subramanyam P., Suryakala D., Subrahmanyam C. Emerging Copper-Based Semiconducting Materials for Photocathodic Applications in Solar Driven Water Splitting. Catal. 2022. V. 12. No 10. P. 1198. https://doi.org/10.3390/catal12101198
8. Mitra D., Kang E.-T., Neoh K.G. Antimicrobial Copper-Based Materials and Coatings: Potential Multifaceted Biomedical Applications. ACS Appl. Mater. Interfaces. 2020. V. 12. No 19. P. 2115921182. https://doi.org/10.1021/acsami.9b17815
9. Tee S.Y., Ponsford D., Lay Ch.E., Wang X., Wang X., Neo D.C.J., Wu T., Thitsartarn W., Yeo J.C.C., Guan G., Lee T.-Ch., Han M.-Y. Thermoelectric Silver-Based Chalcogenides. Adv. Sci. 2022. V. 9. No 36. P. 204624/1-35. 10.1002/advs.202204624
10. Lin S., Li W., Pei Y. Thermally insulative thermoelectric argyrodites. Mater. Today. 2021. V. 48. P. 198-213. https://doi.org/10.1016 /j.mattod. 2021.01.007
11. Semkiv H., Ilchuk N., Kashuba A. Photoluminescence of Ag8SnSe6 argyrodite. Low Temp. Phys. 2022. V. 48. No 1. P. 12. https://doi.org/ 10.1063/ 10.0008957
12. Yang M., Shao G., Wu B., Jiang J., Liu S., Huimin L. Irregularly Shaped Bimetallic Chalcogenide Ag8SnS6 Nanoparticles as Electrocatalysts for Hydrogen Evolution. ACS Appl. Nano Mater. 2021. V. 4. No 7. P. 6745-6751. https://doi.org/ 10.1021/acsanm.1c00769
13. Jiang Q., Li S., Luo Y., Xin J., Li S., Li W., Yang J. Ecofriendly highly robust Ag8SiSe6-based thermoelectric composites with excellent performance near room temperature. ACS Appl. Mater. Interfaces. 2020. V. 12. No 49. P. 54653-54661. https://doi.org/10.1021/acsami.0c15877
14. Fan Y., Wang G., Wang R., Zhang B., Shen X., Jiang P., Zhang X., Gu H., Lu X., Zhou X. Enhanced thermoelectric properties of p-type argy-rodites Cu8GeS6 through Cu. J. Alloys Compd. 2020. V. 822. P. 153665. doi: 10.1016/j.jall-com.2020.153665
15. Brammertz G., Vermang B., ElAnzeery H., Saha-yaraj S., Ranjbar S., Meuris M., Poortmans J. Fabrication and characterization of ternary Cu8SiS6 and Cu8SiSe6 thin film layers for optoelectronic applications. Thin Sol. Films. 2016. V. 616. P. 649654. https://doi.org/10.1016/ j.tsf.2016.09.049
16. Schwarzmüller S., Souchay D., Günther D., Gocke A., Dovgaliuk I., Miller S.A., Snyder G.J., Oeckler O. Argyrodite-Type Cu8GeSe6-xTex (0<x<2): Temperature-Dependent Crystal Structure and Thermoelectric Properties. Z. Anorg. Allg. Chem. 2018. V. 644. No 24. P. 1915-192. doi: 10.1002/zaac .201800453
17. Jiang B., Qiu P., Eikeland E., Chen H., Song Q., Ren D., Zhang T., Yang J., Iversen B.B., Shi X., Chen L. Cu8GeSe6-based thermoelectric materials with an argyrodite structure. J. Mater. Chem. C. 2017. V. 5. P. 943-952. https://doi.org/10.1039/ C6TC05068A
18. Shen X., Xia Y., Yang C., Zhang Z., Li S., Tung Y., Benton A., Zhang X., Lu X., Wang G., He J., Zhou X. High Thermoelectric Performance in SulfideType Argyrodites Compound Ag8Sn(S1-xSex)6 Enabled by Ultralow Lattice Thermal Conductivity and Extended Cubic Phase Regime. Adv. Funct. Mater. 2020. V. 30. P. 2000526/1-10. https://doi.org/ 10.1002/adfm.202000526
19. Charoenphakdee A., Kurosaki K., Muta H., Uno M., Yamanaka S. Ag8SiTe6: A New Thermoelectric Material with Low Thermal Conductivity. Jpn. J. Appl. Phys. 2009. V. 48. P. 011603/1-3. DOI 10.1143/JJAP.48.011603
20. Ivanov-Shits A.K., Murin I.V. Ionika tverdogo tela (Ionics of Solids). St. Petersburg: Petersburg State University, 2000.
21. Li L., Liu Y., Dai J., Hong A., Zeng M., Yan Z., Xu J., Zhang D., Shan D., Liu S., Ren Zh., Liu J.-M. High thermoelectric performance of superionic argyrodite compound Ag8SnSe6. J. Mater. Chem. C. 2016. V. 4. P. 5806-5813. https://doi.org/ 10.1039/C6TC00810K
22. Sardarly R.M., Ashirov G.M., Mashadiyeva L.F., Aliyeva N.A., Salmanov F.T., Agayeva R.Sh., Mamedov R.A., Babanly M.B. Ionic conductivity of the Ag8GeSe6 compound. Mod. Phys. Lett. B. 2023. V. 36. P. 2250171. https:// doi.org/10.1142/S0217984922501718
23. Studenyak I.P., Pogodin A.I., Studenyak V.I., Izai V.Y., Filep M.J., Kokhan O.P., Kus P. Electrical properties of copper- and silver-containing superionic (Cui-xAgx)7SiS5I mixed crystals with argyrodite structure. Sol. State Ion. 2020. V. 345. P. 115183. https://doi.org/10.1016/ j.ssi.2019.115183
24. Heep B.K., Weldert K.S., Krysiak Y., Day T.W., Zeier W.G., Kolb U., Snyder G.J., Tremel W. High electron mobility and disorder induced by silver ion migration lead to good thermoelectric performance in the argyrodite Ag8SiSe6. Chem. Mater. 2017. V. 29. No 11. P. 4833-4839. https://doi.org/10.1021/acs.chemmater.7b00767
25. Li W., Lin S., Ge B., Yang J., Zhang W., Pei Y. Low Sound Velocity Contributing to the High Thermoelectric Performance of Ag8SnSe6. Adv. Sci. 2016. V. 3. No 11. P. 1600196. https:// doi.org/10.1002/advs.201600196
26. Weldert K.S., Zeier W.G., Day T.W., Panthofer M., Snyder G.J., Tremel W. (). Thermoelectric transport in Cu7PSe6 with high copper ionic mobility J. Am. Chem. Soc. 2014. V. 136. P. 1203512040. https://doi.org/10.1021/ja5056092
27. West D.R.F. Ternary Phase Diagrams in Materials Science. 3rd Edition. CRC Press, 2019
28. Saka H. Introduction To Phase Diagrams In Materials Science And Engineering. World Scientific Publishing Company, 2020
29. Babanly M.B., Mashadiyeva L.F., Babanly D.M., Imamaliyeva S.Z., Tagiyev D.B., Yusibov Yu.A. Some issues of complex investigation of the phase equilibria and thermodynamic properties of the ternary chalcogenide systems by the EMF method. Russ. J. Inorg. 2019. V. 64. № 13. P. 1649-1671. DOI: 10.1134/S0036023619130035
30. Imamaliyeva S.Z., Babanly D.M., Tagiev D.B., Babanly M.B. Physicochemical Aspects of Development of Multicomponent Chalcogenide Phases Having the Tl5Te3 Structure: A Review. Russ. J. Inorg. 2018. V. 63. No 13. P. 1703-1730. https://doi.org/10.1134/S0036023618130041
31. Imamaliyeva S.Z., Alakbarzade G.I., Mamedov A.N., Babanly M.B. Modeling the phase diagrams of the Tl9SmTe6-Tl4PbTe3 and Tl9SmTe6-Tl9BiTe6 systems. Azerb. Chem. J. 2020. V. 4. P. 12-16. DOI: 10.32737/0005-2531-2020-4-12-16
32. Mammadov F.M., Amiraslanov I.R., Efendiyeva N.N., Imamaliyeva S.Z. Phase diagrams of the FeGa2S4-FeIn2S4 and FeS-FeGaInS4 systems. Chemical Problems. 2019. P. 58-65. doi: 10.32737/22218688-2019-1-58-65
33. Imamaliyeva S.Z., Mamedov A.N., Babanly M.B. Modeling the phase diagram of the Tl9GdTe6-Tl4PbTe3-Tl9BiTe6 system. New Mater. Compd. Appl. 2021. V. 2. P. 142-149. DOI: 10.1007/978-3-030-64058-3_60
34. Ashirov G.M. Phase equilibria in the Ag8SiTe6-Ag8GeTe6 system. Azerb. Chemical Journal. 2022. V. 1. P. 89-93. doi.org/10.32737/0005-2531-2022-1-89-93
35. Alverdiyev I.J., Aliev Z.S., Bagheri S.M., Masha-diyeva L.F., Yusibov Y.A., Babanly M.B. Study of the 2Cu2S+GeSe2^Cu2Se+GeS2 reciprocal system and thermodynamic properties of the Cu8GeS6-xSex solid solutions. J. Alloys Compd. 2017. V. 691. P. 255-262. doi:10.1016/J.JALL C0M.2016.08.251
36. Aliyeva Z.M., Bagheri S.M., Aliev Z.S., Alverdiyev I.J., Yusibov Yu.A., Babanly M.B. The phase equilibria in the Ag2S-Ag8GeS6-Ag8SnS6 system. J. Alloys Compd. 2014. V. 611. P. 395400. https://doi.org/10.1016/jjallcom.2014.05.112
37. Aliyeva Z.M., Bagheri S.M., Alverdiyev I.J., Yusibov Yu.A., Babanly M.B. Phase equilibria in the quasi-ternary system Ag2Se-Ag8GeSe6-Ag8SnSe6. Inorg. Mater. 2014. V. 50. No 10. P. 981-986. DOI: 10.1134/S002016851410001X
38. Abbasova V.A., Alverdiyev I.J., Mashadiyeva L.F., Yusibov Yu.A., Babanly M.B. Phase relations in the Cu8GeSe6-Ag8GeSe6 system and some properties of solid solutions. Azerb. Chem. J. 2017. V. 1. P. 30-33.
39. Alverdiyev I.J., Bagheri S.M., Aliev Z.M., Yusibov Y.A., Babanly M.B. Phase equilibria in the Ag2Se-GeSe2-SnSe2 system and thermodynamic properties of the solid solutions Ag8Gei-xSnxSe6. Inorg. Mater.
2017. V. 53. No 8. P. 886-896. doi: 10.1134/ S0020168517080027
40. Mashadieva L.F., Alieva Z.M., Mirzoeva R.Dzh., Yusibov Yu.A., Shevel'kov A.V., Babanly M.B. Phase Equilibria in the Cu2Se-GeSe2-SnSe2 System. Russ. J. Inorg. 2022. V. 67. No 5. P. 670682. https://doi.org/10.1134/S0036023622050126
41. Gorochov O. Les composés Ag8MX6 (M= Si, Ge, Sn et X= S, Se, Te). Bull. Soc. chim. Fr. 1968. V. 101. P. 2263-2275.
42. Boivin J.C., Thomas D., Tridot G. Contribution a l'etude des Systèmes: sulfure de silicium et sulfure de cuivre ou d'argent. C. r. séances Acad. sci., Vie acad. 1967. V. 264. No 16. P. 1286-1289.
43. Cambi L., Elli M. Sui sulfogermanati: argirodite sintetica. Atti della Accademia Nazionale dei Lin-cei, Classe di Scienze Fisiche, Matematiche e Naturali, Rendiconti. 1961. V. 30. P. 11-15.
44. Venkatraman M., Blachnik R., Schlieper A. The phase diagrams of M2X-SiX2 (M is Cu, Ag; X is S, Se). Thermochim. 1995. V. 249. P. 13-20. https://doi.org/10.1016/0040-6031(95)90666-5
45. Kogut Y.M. Phase Equilibria and Glass Formation in the Ag2X-PbX-GeX2 (X=S, Se) and Related Systems. Ph.D. (Chemistry) Thesis. 2017
46. Krebs B., Mandt J. Zur Kenntnis des Argyrodit-Strukturtyps: die Kristallstruktur von Ag8SiS6. Z. Naturforsch. B. 1977. V. 32. P. 373-379.
47. Kuhs W.F., Nitsche R., Scheunemann K. The ar-gyrodites - A new family of tetrahedrally close-packed structures. Mater. Res. Bull. 1979. V. 14. No 2. P. 241-248. https://doi.org/10.1016/0025-5408(79)90125-9
48. Boucher F., Evain M., Brec R. Single-Crystal Structure Determination of y-Ag8SiTe6 and Powder X-ray Study of Low-Temperature a and ß Phases. J. Solid State Chem.1992. V. 100. P. 341-355. https://doi.org/10.1016/0022-4596(92)90109-9
49. International Centre for Diffraction Data. ICDD.PDF-2012
Ag8SiS6-Ag8SiTe6 SÏSTEMÏNDO FAZA TARAZLIQLARI VO BORK MOHLULLARIN XARAKTERiZO
EDÏLMOSÏ
A.C.Omiraslanova, K.N.Babanli, S.Zjmamaliyeva, i.C.Olverdiyev, Y.O.Yusibov
Argirodit ailasi birlaçmalari va onlar asasinda fazalar termoelektrik, fotoelektrik, optik va digar xassalara malik qiymatli ekoloji tahlükasiz funksional materiallardir. Onlar hamçinin Cu+ va Ag+ kationlarina göra ion keçiriciliyina malikdirlar va elektrokimyavi sensorlar, elektrodlar, elektrokimyavi enerji çevirici cihazlarda elektrolit materiallari va s. kimi istifada oluna bilarlar. Bu içda Ag8SiS6-Ag8SiTe6 sisteminda faza tarazliqlari differensial termiki analizi va rentgen faza analizi üsullan ila tadqiq edilmiç va sistemin T-x faza diaqrami qurulmuçdur. Müayyan edilmiçdir ki, sistem kvazibinardir va Ag8SiTe6 va HT- Ag8SiS6 birlaçmalari arasinda qeyri-mahdud avazolunma bark mahlullarin amala galmasi ila xarakteriza olunur. Bark mahlullarin amala galmasi ila Ag8SiS6 birlaçmasinin polimorf keçid temperaturu azalir. Bu, >30 mol.% Ag8SiTe6 tarkibli ion keçirici kubik fazanin otaq temperaturunda va daha açagida stabillaçmasina gatirib çixarir. RT- Ag8SiS6 asasinda homogenlik sahasi 10 mol.% taçkil edir. Toz difraktoqramlari asasinda bark mahlullarin kristal qafas parametrlari hesablanmiç va onlann tarkibdan xatti asili olmasi gôstarilmiçdir.
Açar sözlzr: gümü§-silisium sulfid, gümü§-silisium tellurid, faza tarazliqlari, bark mahlullar, polimorf çevrilma.
ФАЗОВЫЕ СООТНОШЕНИЯ В СИСТЕМЕ Ag8SiS6-Ag8SiTe6 И ХАРАКТЕРИСТИКИ ТВЕРДЫХ РАСТВОРОВ
А.Дж.Амирасланова, К.Н.Бабанлы, С.З.Имамалиева, И.Дж.Алвердиев, Ю.А.Юсибов
Соединения семейства аргиродита и фазы на их основе относятся к ценным экологически безопасным функциональным материалам, проявляющим термоэлектрические, фотоэлектрические, оптические и другие свойства. Они также обладают ионной проводимостью по катионам Си+ и Ag+ и могут быть использованы в качестве электрохимических сенсоров, электродов или электролитных материалов в устройствах электрохимического преобразования энергии. В данной работе методами дифференциального термического и рентгенофазового анализа изучены фазовые равновесия в системе Ag8SiS6-Ag8SiTe6 и построена Т-х фазовая диаграмма. Установлено, что система квазибинарна и характеризуется образованием непрерывного ряда твердых растворов замещения между соединениями Ag8SiTe6 и НТ- Ag8SiS6. При образовании твердых растворов температура полиморфного перехода Ag8SiS6 понижается. Это приводит к стабилизации ионопроводящей кубической фазы в области составов >30 мол.% Ag8SiTe6 при комнатной температуре и ниже. Область гомогенности на основе RT-Ag8SiS6 составляет 10 мол.%. По данным порошковых дифрактограмм рассчитаны параметры кристаллической решетки полученных твердых растворов и показана их линейная зависимость от состава.
Ключевые слова: сульфид серебра-кремния, теллурид серебра-кремния, фазовые равновесия, твердые растворы, полиморфное превращение.
