CC BY
22
22 AZERBAIJAN CHEMICAL JOURNAL № 1 2023 ISSN 2522-1841 (Online)
ISSN 0005-2531 (Print)
UDC 544.344.015.3: 546.5722/24
Ag8GeS6(Se6)-Ag8GeTe6 SYSTEMS: PHASE RELATIONS, SYNTHESIS, AND CHARACTERIZATION OF SOLID SOLUTIONS
A.J-Amiraslanova1, A.T.Mammadova1, I.J.Alverdiyev\ Yu.A.Yusibov,1 M.B.Babanly2
1Ganja State University
2 M.Nagiyev Institute of Catalysis and Inorganic Chemistry, Ministry of Science and Education
of the Republic of Azerbaijan
Received 25.08.2022 Accepted 16.09.2022
Phase equilibria in the Ag8GeS6-Ag8GeTe6 and Ag8GeSe6-Ag8GeTe6 systems were studied using differential thermal analysis and powder X-ray diffraction technique. The T-x phase diagrams were constructed. It has been found that both systems are partially quasi-binary and are characterized by the formation of continuous series of substitutional solid solutions between Ag8GeTe6 and high-temperature cubic modifications of Ag8GeS6 and Ag8GeSe6. When solid solutions are formed, the temperatures of polymorphic phase transitions of these compounds decrease. This leads to the stabilization of the ion-conducting cubic phase in the >40 mol% Ag8GeTe6 range of compositions at room temperature and below. The regions of homogeneity based on Ag8GeS6 and Ag8GeSe6 are 15 and 10 mol.%, respectively. The crystal lattice parameters of the identified solid solutions were calculated from the XRD data, and their linear dependence on the composition is shown.
Keywords: silver-germanium selenide, silver-germanium telluride, phase equilibria, solid solutions, polymorphic transformation.
formation of solid solutions are of particular interest since the material properties can be changed by varying the composition [23-25].
Earlier [26-32] we presented the results of the investigations of the systems in which the wide areas of solid solutions are identified.
In this work, phase equilibria in the Ag8GeS6(Se6)-Ag8GeTe6 systems are studied, and new phases of variable composition are obtained and characterized.
The initial compounds of these systems have been studied in detail. The Ag8GeS6 melts congruently at 1223 K and has a phase transformation at 496 K [6]. High-temperature (HT)-modification of this compound crystallizes in cubic structure (F-43m, a = 1.070 nm [33, 34]), and the room temperature (RT)-modification has an orthorhombic crystal structure (Sp.gr. Pna21, a=1.5149, b=0.7476, c=1.0589 nm [35]).
The Ag8GeSe6 melts congruently at 1178 K and has a phase transformation at 321 K [36]. HT-modification of this compound crystallizes in cubic structure (a = 1.099 nm [33]), and the RT-modification has an orthorhombic crystal
doi.org/10.32737/0005-2531-2023-1-22-29
Introduction
Complex chalcogenides based on silver and copper are the focus of attention of researchers as environmentally friendly functional materials with thermoelectric, photoelectric, optical, and other properties [1-6]. Among these materials, an important place is occupied by compounds of the argyrodite family with the common formula Ag8AIVX6 (AI - Cu, Ag; BIV -Si, Ge, Sn; X - S, Se, Te) and phases based on them [7-12], which, in addition to these properties, also have ionic conductivity for Cu+ and Ag+ cations and can be used as electrochemical sensors, electrodes or electrolyte materials in devices for electrochemical energy conversion -in solid-state batteries, displays, etc. [13-19]. According to [17-19], the presence of mixed electronic-ionic conductivity is one of the significant factors that positively affect the thermoelectric characteristics of these materials.
Understanding the phase relationships in the respective systems is always useful for developing directed methods for the synthesis of new materials [20-22]. Systems characterized by the
structure (Sp.gr. Pmn21, a = 0.7823, b = 0.7712, c = 1.0885 nm [36, 37]).
Literature data on the nature of Ag8GeTe6 melting are contradictory. According to [33, 38], this compound melts with decomposition according to the peritectic reaction at 918 K, and according to [6] - congruently at 916 K. Ag8GeTe6 crystallizes in a cubic lattice (F.gr. F-43m, a = 1.1563 nm) [39].
As can be seen from the literature data, it can be assumed that the (HT) modifications of Ag8GeS6 and Ag8GeSe6 can form continuous series of solid solutions with Ag8GeTe6. On the other hand, the nature of the interaction of low-temperature modifications of these compounds with Ag8GeTe6 should be different.
Materials and methods
The Ag8GeS6, Ag8GeSe6, and Ag8GeTe6 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
_o
in diameter), evacuated to ~10 Pa, and fused.
The synthesis of sulfide- and selenide-containing compounds was carried out as follows. The ampoules were placed in an inclined two-zone furnace for 2/3 of their length. The "hot zone" was slowly heated from room temperature to ~ 30-50 K above the melting point of the synthesized compounds and the outside part of the ampoule was quenched with water ("cold zone"). The "hot zone" plays a role of the interaction zone and the "cold zone" condenses chalcogen and returns it to the interaction zone. As a result of the reaction in the cold
part the mass of the elemental chalcogen decreases and within 1-2 hours it is spent almost. Thereafter, the ampoule was completely placed in a furnace and kept at the pointed temperature for 1 -2 h and cooled with the oven turned off.
Taking into account the data of works [31, 36] about the peritectic nature of Ag8GeTe6 formation after synthesis, it was annealed at 800 K for 300 h.
DTA data were employed for the identification of the synthesized compounds. The melting and polymorphic transition temperatures of Ag8GeS6 and Ag8GeSe6 coincided with the data of [6, 34].
Figure 1 shows the DTA curve of the synthesized Ag8GeTe6 compound. As can be seen, there is one endothermic effect at 917 K on the heating curve, and 2 exothermic effects on the cooling curve: the first at 932 K corresponds to the beginning of crystallization, and the second at 917 K corresponds to the pe-ritectic formation reaction. Thus, we have confirmed the incongruent nature of the melting of the Ag8GeTe6 compound.
All synthesized compounds were also checked by X-ray powder diffraction. All peaks can be indexed as pure phases of Ag8GeS6, Ag8GeSe6, and Ag8GeTe6, with the cell parameters close to the [31-35].
Investigated samples of the Ag8GeS6-Ag8GeTe6 and Ag8GeSe6-Ag8GeTe6 systems were prepared by melting the stoichiometric quantities of the pre-synthesized compounds in sealed silica ampoules under a vacuum.
>
E,
u
Q Œ
- Cooling Á /9,V931
850 900 950 T, K
- Heating 917 /
Fig.1. DSC curve of heating and cooling of the Ag8GeTe6 compound.
Alloys were heated up to 1250 K and held at this temperature for about 1 h and then were annealed at 800 K for about 500 h. For some compositions were prepared two different sets of alloys: the first series after annealing were slowly cooled down to room temperature, and the second series were quenched in cold water after annealing.
DTA and XRD techniques were employed to analyze the samples. The XRD data were collected at room temperature using a Bruker D8 ADVANCE diffractometer (with Cu-Ka1 radiation). DTA of the equilibrated alloys was carried out using an NETZSCH 404 F1 Pegasus system device. The heating rate was 10 K/min
Results and discussion
The phase diagram of the Ag8GeS6-Ag8GeTe6 and Ag8GeSe6-Ag8GeTe6 systems were constructed based on DTA results (Table 1). As can be seen from Figure 2, both systems are partially quasi-binary. Their quasi-binarity is violated in the composition regions rich in Ag8GeTe6 due to the incongruent nature of the melting of this compound. In the indicated areas of the T-diagrams of both systems, we noted narrow regions of primary crystallization of the P-phase based on the intermediate modification of Ag2Te and a three-phase region L+P'+5. According to the phase diagrams, continuous series of solid solutions (5-phase) between Ag8GeTe6 and high-temperature modifications of the Ag8GeS6 and Ag8GeSe6 compounds are formed in both systems.
Table 1. The DTA results for the alloys of the Ag8GeS6-Ag8GeTe6 and Ag8GeSe6-Ag8GeTe6 systems
Ag8GeS6-Ag8GeTe6 system Ag8GeSe6-Ag8GeTe6 system
Composition, mol% Ag8GeTe6 Thermal effects, K Composition, mol% Ag8GeSe6 Thermal effects, K
0 (Ag8GeS6) 490;1223 0 (Ag8GeS6) 323;1178
10 432-465; 1183-1205 10 319; 1147-1163
20 415; 1143-1180 20 1118-1140
30 1112-1153 30 1090-1170
40 1085-1122 40 1070-1095
50 1046-1093 50 1040-1070
60 1015-1065 60 1025-1051
70 993-1036 70 995-1028
80 957-998 80 972-1000
90 930-961 90 940-962
100 918; 932 100 918; 932
Fig. 2. Phase diagrams of the Ag8GeS6-Ag8GeTe6 and Ag8GeSe6-Ag8GeTe6 systems.
In the studied systems, the phase transition temperatures of Ag8GeS6 (495 K) and Ag8GeSe6 (323 K) decrease with the formation of solid solutions, and no thermal effects corresponding to these transitions are observed on the DTA curves of alloys containing 30 mol% or more Ag8GeTe6. This shows that the temperatures of these transitions are below room temperature in the specified ranges of compositions.
The XRD data confirm the plotted phase diagrams. The XRD data of the alloys slowly cooled after annealing (Figures 3, 4) showed that in the Ag8GeS6-Ag8GeTe6 system, the 20 mol% Ag8GeTe6 alloy has a diffraction pattern identical to that of the low-temperature modifi-
cation Ag8GeS6, while alloys richer in Ag8GeTe6 have a cubic diffraction pattern that is qualitatively similar to Ag8GeTe6.
The powder XRD patterns for starting compounds and solid solutions were indexed using Topas V3.0 software (Table 2). The comparative analysis of the data in Table 2 showed that in the region of >40 mol% Ag8GeTe6 the solid solutions at room temperature have a cubic structure. All samples and starting compounds quenched from 800K have a cubic structure also (Table 2). The concentration dependence of the cubic lattice parameters for HT solid solutions follows Vegard's rule (Figure 5).
Fig.3. Powder diffractograms of some alloys of the Ag8GeS6-Ag8GeTe6 system.
Fig.4. Powder diffractograms of some alloys of the Ag8GeSe6-Ag8GeTe6 system
Table 2. Crystallographic parameters of phases in the Ag8GeS6-Ag8GeTe6 and Ag8GeSe6-Ag8GeTe6 systems
System Composition, mol% Syngony, Sp.Gr., lattice parameters, nm
Ag8GeTe6 Room temperature Quenched from 800 K
e [— 0 (Ag8GeS6) Orthoromb. (Pna21): a=1.5128(4); 6=0.7458(2); c=1.0554(3) Cubik: (F43m): a=1.0707(3)
<D O 8 g8 <c - CO 20 Orthoromb. (Pna21): a=1.5286(4); 6=0.7546(3); c=1.0687(3) -"-, a=1.0887(4)
40 Cubik: (F43m): a=1.1058(3) -"-, a=1.1063(4)
<D O 60 -"-, a=1.2435(3) -"-, a=1.1242(4)
60 <c 80 -"-, a=1.1392(4) -"-, a=1.1397(4)
Ag8GeTe6 -"-, a=1.1567(4) -"-, a=1.1572(4)
e T 0 (Ag8GeSe6) Orthoromb. (Pna2j): a=0.7841(2); 6=0.7732(2); c=1.0911(3) Cubik: (F43m): a=1.0989(3)
O 8 eg 20 Biphasic: y+8 -"-, a=1.1105(4)
<c 1 6 40 Cubik: (F43m): a=1.1205(3) -"-, a=1.1211(4)
<D m e O 00 sO <C 60 -"-, a=1.1327(4) -"-, a=1.1335(4)
80 -"-, a=1.1452(4) -"-, a=1.1456(4)
Ag8GeTe6 -"-, a=1.1567(4) -"-, a=1.1572(4)
Fig.5. Dependences of the period of the cubic lattice of solid solutions on the composition in the Ag8GeS6-Ag8GeTe6 (1) and Ag8GeSe6-Ag8GeTe6 (2) systems
Conclusion
Based on the DTA and XRD data, we obtained new patterns of phase equilibria in the Ag8GeS6-Ag8GeTe6 and Ag8GeSe6-Ag8GeTe6 systems. It has been established that both systems are partially quasibinary and are characterized by the formation of continuous series of substitutional solid solutions (5-phase) between Ag8GeTe6 and high-temperature cubic modifications of Ag8GeS6 and Ag8GeSe6. The formation of solid solutions is accompanied by a decrease in the temperatures of polymorphic phase transitions of these compounds, which leads to the stabilization of ion-conducting solid solutions of compositions >40 mol% Ag8GeTe6 at room temperature and below. The homogeneity regions based on Ag8GeS6 and Ag8GeSe6 are 15 and 8 mol.%, respectively.
References
1. Applications of Chalcogenides: S, Se, and Te. Ed. by Ahluwalia G.K. Springer. 2016, 461 p.
2. Chalcogenides: Advances in Research and Applications. Ed. Woodrow P. Nova. 2018. 111 p.
3. Chalcogenide. From 3D to 2D and Beyond. Ed. By Liu, X., Lee, S., Furdyna, J.K., Luo, T., Zhang, Y-H. Elsevier. 2019. 385 p.
4. Scheer R., Schock H-W. Chalcogenide Photo-voltaics: Physics, Technologies, and Thin Film Devices. Wiley-VCH. 2011. 384 p.
5. Alonso-Vante N. Chalcogenide Materials for Energy Conversion: Pathways to Oxygen and Hydrogen Reactions. Springer. 2018. 226 p.
6. Babanly, M.B., Yusibov Yu.A., and Abishev, V.T. Ternary chalcogenides on the base of copper and silver (In Russian), Baku: BGU. 1993. 342 p.
7. Lin S., Li W., Pei Y. Thermally insulative thermoelectric argyrodites. Materials Today, 2021. V.48. P.198-213.
8. Fujikane M., Kurosaki K., Muta H., Yamanaka Sh. Thermoelectric properties of Ag8GeTe6. J. Alloys Compd. 2005. V. 396 (1-2). P. 280.
9. 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 (49). P. 54653.
10. 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 argyrodites Cu8GeS6 through Cu vacancy. J. Alloys Compd. 2020. V.822. P.153665.
11. Semkiv H., Ilchuk N., Kashuba A. Photoluminescence of Ag8SnSe6 argyrodite, Low Temp. Phys. 2022. V. 48 (1). P.12.
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(7). P.6745. doi.org/10.1021/acsanm.1c00769
13. Ivanov-Shits A.K., Murin I.V. Solid State Ionics (In Russian). 2000. V. 1. Sankt-Petersburg. 616 P.
14. 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.
15. 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.
16. 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 (Cu1-xAgx)7SiS5I mixed crystals with argyrodite structure. Solid State Ion. 2020. V.345. P. 115183.
17. 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 (11). P.4833.
18. 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(11), P.1600196.
19. 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. 12035.
20. West D.R.F. Ternary Phase Diagrams in Materials Science. 3rd edition. CRC Press. 2019. 236 p.
21. Saka H. Introduction To Phase Diagrams In Materials Science And Engineering. World Scientific Publishing Company. 2020. 188 p.
22. Babanly M.B., Mashadiyeva L.F., Babanly D.M., Imamaliyeva S.Z., Tagiyev D.B., Yusibov Yu.A. Some aspects of complex investigation of the phase equilibria and thermodynamic properties of the ternary chalcogenid systems by the EMF method. Russ. J. Inorg. Chem. 2019. V. 64(13). P. 1649.
23. Imamaliyeva S.Z., Babanly D.M., Tagiev D.B., and Babanly M.B. Physicochemical Aspects of Development of Multicomponent Chalcogenide Phases Having the Tl5Te3 Structure: A Review. Russ. J. Inorg. Chem. 2018. V. 63. № 13. P. 1703.
24. 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. № 4. P. 12-16.
25. Ashirov G.M. Phase equilibria in the Ag8SiTe6-Ag8GeTe6 system. Azerb. Chem. J. 2022. № 1. P. 89-93
26. Alverdiyev I.J., Aliev Z.S., Bagheri S.M., Mashadiyeva L.F., Yusibov Y.A., Babanly M.B. Study of the 2Cu2S+GeSe2 o-Cu2Se+GeS2 reciprocal system and thermodynamic properties of the
Cu8GeS6_xSex solid solutions. J.Alloys Compd. 2017. V.691. P.255-262
27. 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.
28. 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. №10. P. 981-986
29. Abbasova V.A., Alverdiyev I.J., Mashadiyeva L.F., Yusibov Y.A., Babanly M.B. Phase relations in the Cu8GeSe6-Ag8GeSe6 system and some properties of solid solutions. Azerb. Chem. J. 2017. № 1. P.30-33
30. Alverdiyev I.J., Bagheri S.M., Aliyeva Z.M., Yusibov Yu.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. № 8. P. 886-896
31. Yusibov Yu.A., Alverdiev I.Dzh., Mashadieva L. F., Babanly D.M., Mamedov A.N., Babanly M.B. Experimental Study and 3D Modeling of the Phase Diagram of the Ag-Sn-Se System. Russ. J. Inorg. Chem. 2018. V. 63. No. 12. P. 1622-1635
32. 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. Chem. 2022. V. 67. No 5. P. 670-682
33. Gorochov O. Les composés Ag8MX6 (M = Si, Ge, Sn et X = S, Se, Te). Bull. Soc. Chim. Fr. 1968. № 6. P. 2263-2275.
34. Prince A. Silver-germanium-sulfur. In: Ternary Alloys. V. 2. VCH. 1988. P.196-202
35. Eulenberger G. Die Kristallstruktur der Tieftemperaturmodifikation von Ag8GeS6. Synthetischer Argyrodit. Monatsh. Chem. 1977. V. 108. P. 901913.
36. Yusibov Y.A., Alverdiyev I.DZh, Ibrahimova F.S., Mamedov A.N., Tagiyev D.B., Babanly M.B. Study and 3D modeling of the phase diagram of the Ag-Ge-Se system. Russ. J. Inorg. Chem. 2017. V. 62. № 5. P. 1232-1242
37. Carré D., Ollitrault Fichet R., Flahaut J. Structure de Ag8GeSe6-ß. Acta Crystallogr. B. 1980. V. 36. P.245-249.
38. Li J.Q., Li L.F., Song S.H., Liu F.S., Ao W. Q. High thermoelectric performance of GeTe-Ag8GeTe6 eutectic composites. J.Alloys Compd. 2013. V. 565. P. 144-147.
39. Rysanek N., Laruelle P., Katty, A. Structure cristalline de Ag8GeTe6 (y). Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry. 1976. V. 32. No 3. P. 692-696.
Ag8GeS6(Se6)-Ag8GeTe6 SiSTEMLORi: FAZA TARAZLIQLARI, BORK MOHLULLARIN SÏNTEZÏ
VO XARAKTERiZO EDILMOSi
A.C.Omiraslanova, A.T.Mamm3dova, I.C.Alverdiyev, Yu.O.Yusibov, M.B.Babanli
DTA va RFA üsullan ils Ag8GeS6-Ag8GeTe6 va Ag8GeSe6-Ag8GeTe6 sistemlari tadqiq edilmiç, onlann T-x faza diaqramlan qurulmuçdur. Müayyan edilmiçdir ki, har iki sistem qisman kvazibinar olub, Ag8GeTe6 ila Ag8GeS6 va Ag8GeSe6 birlaçmalarinin yüksak temperaturlu kubik modifikasiyalari arasinda fasilasiz avazolunma bark mahlullari amala gatirir. Bark mahlullarin amala galmasi bu birlaçmalarin polimorf çevrilma temperaturlarinin azalmasi ila mûçaiyat olunur. Bu, >40 mol% Ag8GeTe6 qatiliq sahasinda ionkeçirici kubik fazanin otaq temperaturunda va daha açagi temperaturlarda stabillaçmasina gatirib çixarir. Otaq temperaturunda Ag8GeS6 va Ag8GeSe6 birlaçmalarinin açagitemperaturlu modifikasiyalari asasinda hallolma müvafiq olaraq 15 va 10 mol.% taçkil edir. Toz difraktoqramlari asasinda bark mahlullann kristal qafas parametrlari hesablanmiç, onlarin takribdan xatti asili olmasi müayyan edilmiçdir.
Açar sözlzr: gümü§-germanium selenid, gümü§-germanium tellurid, faza tarazligi, Ьэгк шэЫиПаг, polimorf keçid.
СИСТЕМЫ Ag8GeS6(Se6)-Ag8GeTe6: ФАЗОВЫЕ СООТНОШЕНИЯ, СИНТЕЗ И ХАРАКТЕРИСТИКА ТВЕРДЫХ РАСТВОРОВ
А.Дж.Амирасланова, А.Т.Мамедова, И.Дж.Алвердиев, Ю.А.Юсибов, М.Б.Бабанлы
Методами дифференциально-термического анализа и рентгенофазового анализа исследованы фазовые равновесия в системах Ag8GeS6-Ag8GeTe6 и Ag8GeSe6-Ag8GeTe6, построены их Т-х фазовые диаграммы. Установлено, что обе системы являются частично квазибинарными и характеризуются образованием непрерывного ряда твердых растворов замещения между Ag8GeTe6 и высокотемпературными кубическими модификациями Ag8GeS6 и Ag8GeSe6. При образовании твердых растворов температуры полиморфных фазовых переходов этих соединений понижаются. Это приводит к стабилизации ионопроводящей кубической фазы в области составов >40 мол. % Ag8GeTe6 при комнатной температуре и ниже. Области гомогенности на основе Ag8GeS6 и Ag8GeSe6 составляют 15 и 10 мол.% соответственно. Из данных порошковых дифрактограмм рассчитаны параметры кристаллических решеток выявленных твердых растворов и показана их линейная зависимость от состава.
Ключевые слова: селенид серебра-германия, теллурид серебра-германия, фазовые равновесия, твердые растворы, полиморфное превращение.
