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ISSN 2522-1841 (Online) AZERBAIJAN CHEMICAL JOURNAL № 1 2023 55
ISSN 0005-2531 (Print)
UDC-546 [ 681.21.22.641.663]
PHASE EQUILIBRIUM IN THE QUASI-TERNARY SYSTEM Y2O2S-Ga2S3-Tb2O2S
I.B.Bakhtiyarli, V.S.Mammadov, Z.M.Mukhtarova, A.S.Abdullayeva*
M.Nagiyev Institute of Catalysis and Inorganic Chemistry, Ministry of Science and Education of the
Republic of Azerbaijan *Azerbaijan University of Architecture and Construction
[email protected] [email protected]
Received 17.10.2022 Accepted 25.11.2022
The results of the study of quasibinary (lateral) and non-quasibinary polythermal sections in quadrilateral systems Y2O2S-Ga2S3-Tb2O2S show the prognosis of the established liquidity surface, where the nature of the chemical interaction is relatively simple. Thus, the Ga2S3-Y2O2S va Ga2S3-Tb2O2S sides of a quasi-triangular system are quasi-binary eutectic systems with a limited solubility based on both components. On the Y2O2S-Tb2O2S side, a continuous solid solution area is formed. Thus, in the Y2O2S-Ga2S3-Tb2O2S quasi-triangular system, crystallization ends not at the non-variant triple point, but at the low-temperature binary non-variant (eutectic e1).
Keywords: lanthanoids oxysulfides, system components, quasitrack system, mono-variant, non-variant, eutectic, peritectic.
doi.org/10.32737/0005-2531-2023-1-55-63
Introduction
As you know, in the current stage of development of electronics, it is very important for the optoelectronics industry to obtain the maximum brightness of the narrow spectrum and increase the technological parameters of radiation. In this regard, mixed cationic oxysul-fides of lanthanides are the main phosphors in various functional electronics, depending on the type of excitation and the wavelength of radiation. Solid solutions based on lanthanoid oxysulfides can successfully replace the currently used traditional phosphors [1-3]. Thus, the solid solutions formed in the system Ln2O2S-Ln/2O2S (Ln - 4 f half-level empty, half-filled and full: i = 0,7,14) are unique in X-ray, high light output during cathode excitation, technological and spectral properties due to their properties, they can be used in the manufacture of X-ray screens, X-ray thin films, electron ray tubes and electronic optical converters. These materials are thermally and chemically resistant to sulfide phosphors and do not require any stabilizers when preparing the suspension [4-8].
Therefore, the study of phase equilibrium
in the quasi-triangular system Y2O2S-Ga2S3-Tb2O2S, the study of physical and chemical properties of the obtained new phases were more relevant from a scientific and practical point of view.
Experimental part
For the experiment, the alloys were prepared in the stoichiometric composition from the components of the quasi-triple system Y2O2S-Ga2S3-Tb2O2S (Y2O2S, |3-Ga2S3,Tb2O2S). P-Ga2S3 was obtained by synthesis of elements (Ga - r^-000. S-B-5) by a single method [9]. The lattice constants [10] were taken as a commercial reagent for Y2O2S and Tb2O2S, respectively.
The synthesis of Ga2S3, Tb2O2S and the alloys used as the starting material was prepared by the ceramic method and carried out in a vertical oven at 1375-1425 K for 6 hours by the method of ampoules with a single air (0.133 Pa). The samples were thermally treated at 1000 K for 450 h to homogenize [11].
Equilibrium samples were studied by complex methods of physicochemical analysis (differential thermal (DTA), XRD, microstructure (MSA), determination of microhard-ness and density).
DTA - was studied using a STA 449 F3 Jupiter synchronous thermal analysis system, manufactured by DTA-NETZSCH (Germany).
The heating rate was 15 degrees / min.
XRD - was studied using D2 Phaser Bruker automatic diffractometer (CuKa-ra-diation, Ni-filter) made in Germany. Scanning speed 2 degrees/min. was.
MSA - was carried out on a polished surface using METAM-PB microscopes produced by OAO LOMO and MC-500 microscopes produced by Mikros, Austria.
Determination of microhardness was carried out on PMT-3 device.
The density was determined pycnomet-rically and toluene was used as a filler.
Results and discussion
Chemical interactions of the quasi-ternary system Y2O2S-Ga2S3-Tb2O2S were studied in three quasi-binary Ga2S3-Y2O2S, Ga2S3-Tb2O2S, Y2O2S-Tb2O2S and four non-quasi-binary Ga2S3-(Y2O2S)0.50(Tb2O2S)0.50(b), (Y2O2S)0.50(Tb2O2S)0.50(b)-(Ga2S3)o.8o(Tb2O2S)o.2o(e2), Y2O2S-(Ga2S3)0.80(Tb2O2S)0.20 (e2) and Tb2O2S-(Ga2S3)0.75(Y2O2S)0.25 (a). The Ga2S3-Y2O2S system has been studied in the literature [2]. The system is quasi-binary and the phase diagram is eutectic. Eutectic point coordinates: 14 mol% Y2O2S, 1320 K. 295 K has a solubility area of 3 mol% based on Ga2S3 and 6 mol% based on Y2O2S.
For the study of the Ga2S3, Tb2O2S system 14 samples were synthesized according to
the compositions shown in the table. Sampling of the initial components (Ga2S3, Tb2O2S) was carried out in a single-temperature vertical oven from a quartz ampoule by the ceramic method at 1400 K temperature for 6 hours.
The synthesized samples were subjected to heat treatment for 540 hours at 1200 K temperature for homogenization.
Samples rich in Ga2S3 are gray, the remaining components are yellowish white.
The samples were investigated by measuring DTA, XRD, MSA, microhardness and density.
The four-dimensional effect was observed on thermograms obtained in alloys containing ~10 mol.% Tb2O2S during DTA. They also characterize the phase transition in the liquid solution region based on liquid and Ga2S3. Of the effects observed in other alloys, high-temperature fluidity is a eutectoid phase transition y(Ga2S3)^P(Ga2S3) at 1280 K and eutectic equilibrium at 1330 K. 50 mol.%
Since alloys above Tb2O2S did not melt, no liquidus temperature was observed. MSA, carried out on a polished surface, shows that an alloy containing 6 mol.% Tb2O2S, is singlephase and has a relief of solid solutions. Eutectic and open phase up to 20 mol. % Tb2O2S as the amount of the second component increases; Above 20 mol.% Tb2O2S (up to 50 mol.%), a eu-tectic and a dark phase are observed (Figure 1).
a) b) c)
Fig. 1. Microstructure of alloys in the system Ga2S3-Tb2O2S: a) 4 mol% Tb2O2S, b) 10 mol% Tb2O2S, c) 30 mol% Tb2O2S.
According to the results of MSA, when measuring microhardness, two values were obtained: - (Ga2S3) corresponding to 5000-5005 mPa and 5100 mPa belonging to Tb2O2S (Figure 1). Density values vary between the initial components (3.65^7.56 g/cm3).
XRD patterns showed only the diffract-
tion bands of the primary components Ga2S3 ICDD-00-016-0500; Tb2O2S ICDD- 01-0746680 (Figure 2).
A phase diagram of the Ga2S3-Tb2O2S system was drawn based on the results of DTA, MSA, XRD and measurements of microhard-ness and density (Figure 3).
Table. Results from the measurement of DTA, microhardness, density of alloys of the Ga2S3-Tb2O2S system
Composition mol% Thermal effects, T, K Microhardness, mPa Density, g/cm3
Ga2S3 Tb2O2S ß(Ga2S3) a(Tb2O2S)
100 - 1295, 1395 5000 - 3.65
95 5 1260, 1280, 1360, 1390 5005 - 3.75
90 10 1260, 1335, 1380 5005 5100 3.85
80 20 1260, 1330 evt evt 4.08
75 25 1260, 1330, 1400 5005 5100 4.16
70 30 1260, 1330, 1445 5000 5100 4.32
60 40 1260, 1330, 1530 5000 5100 4.61
50 50 1260, 1335, 1620 5005 5100 4.92
40 60 1255, 1335, 1700 - - 5.31
30 70 1260, 1335, 2190 - - 5.72
20 80 1265, 1330, 2250 - - 6.35
15 85 1255, 1335, 2300 - - 6.56
10 90 2310 - - 6.82
- 100 2350 - 5100 7.56
Tb;0:s
■
1 1 1. ! .......
: . 1 95mol%Tb,0,S I I. ! II, .„ .
A. A ü » II 7i 1 I 1 75mol%Tb,0,S i„ /MÍA TT?
A A J. 1 I IÎ i 50mol%Tb,0,S iL âtiïïïh "TT
'î 1 L 1 20mol%Tb,0;S líW JíflA m
5mol%Tb,0,S
:__I il__I Jii m lil ill III »i
loor
75"
4_U_il lil mi liJ ill lil if._
I0~9 8 7 6 5 4 3 2 d/n,A" 1
Fig. 2. Diffractograms of alloys in the Ga2S3-Tb2O2S system. AZERBAIJAN CHEMICAL JOURNAL № 1 2023
GajSj 20 40 60 80 Tb,0,S mol%
Fig. 3. Phase diagram of the Ga2S3-Tb2O2S system.
It is obvious that from the phase diagram the Ga2S3-Tb2O2S system is quasi-binary and eutectic. The eutectic point is located at the coordinates of 20 mol% Tb2O2S and 1330 K. 6 mol% Tb2O2S based on Ga2S3 and 10 mol% soluble area based on Tb2O2S (only by XRD) were found at 300 K. 1330 K represents the eutectic equilibrium observed in the system, and 1260 K temperature represents the y(Ga2S3)^P(Ga2S3) phase transition.
It was found that the phase transition y(Ga2S3)^P(Ga2S3) is eutectoid, falling from 1290 K to 1260 K under the influence of the second component (Tb2O2S).
Thus, the phase diagram of the system Ga2S3-Tb2O2S was drawn with the help of complex methods of physicochemical analysis. The diagram is quasi-binary and eutectic.
The Ga2S3-Y2O2S system has been studied in the literature [12-16]. The system is quasi-binary and the phase diagram is eutectic. The coordinates of the eutectic point are followings: 14 mol% Y2O2S, 1320K. 295K has a solubility area of 3 mol% based on Ga2S3 and 6 mol% based on Y2O2S.
Based on the literature [17-20], it was found that the Y2O2S-Tb2O2S system is quasi-binary and there is a continuous solid solution area between the initial components. Our ther-modynamic calculations clarified the geometric parameters of the liquidus and solidus curves of the system and studied the dependence of the elemental lattice parameters on the solidity over a wide range of concentrations.
It was revealed that the value of parameter "a" almost does not change depending on the composition. The value of parameter "c" changes slightly monotonously. This once again confirms that there is a continuous solid solution between the components of the Y2O2S-Tb2O2S system.
Thus, it is shown that the two sides of the quasi-ternary system Y2O2S-Ga2S-Tb2O2S: Ga2S3-Y2O2S and Ga2S3-Tb2O2S are eutectic systems with a limited solubility based on both components. In the Tb2O2S-Y2O2S system, a continuous solid solution area is observed between the components.
Fig. 4. a) Phase diagram of the system Y2O2S-Ga2S3-Tb2O2S., b) The dependence of the elemental lattice constants on the solid in the solid solution.
Non-quasi-binary cross-sections studied in the Y2O2S-Ga2S3-Tb2O2S quasi-ternary system. A number of non-quasi-binary cross-sections has been developed to determine the coordinates of the initial crystallization areas of new phases (solid solutions) and the monovariant curves of isotherms obtained in the quasi-triangular system Y2O2S-Ga2S3-Tb2O2S. We would like to bring four of them to your attention.
As in the previous systems studied, the alloys were synthesized from the original components by the ceramic method for the study of these non-quasibinar cross-sections.
Samples were studied by complex methods of physical and chemical analysis (DTA, XRD, MSA, measurement of microhardness, density) after heat treatment at a temperature below 50 K below the solidus temperature. Based on the results obtained, Ga2S3-(Y2O2S)0.50(Tb2O2S)0.50 (b) (I), (Y2O2S)0.50(Tb2O2S)0.50 (b) - (Ga2S3)0.80(Tb2O2S)0.20(e2) (II), Y2O2S-(Ga2S3)0.80(Tb2O2S)0.20(e2) (III) and Tb2O2S-(Ga2S3)0.75(Y2O2S)0.25 (a) (IV). Phase diagram of non-quasibinar sections is constructed (Figure 2). The phase diagrams show that the
nature of the chemical interactions that occur in the Y2O2S-Ga2S3-Tb2O2S quasi-ternary system is relatively simple.
Ga2S3-(Y2O2S)0.50(Tb2O2S)0.50 in the phase diagram of the section the liquidity of all phase diagrams of the non-quasi-binary sections studied, except for the area rich in Ga2S3 (Figure 5 (a)) a a[(Y2O2S)1-x (Tb2O2S)x] consists of a branch that reflects the initial crystallization of the solid solution. As Ga2S3-(Y2O2S)0 50(Tb2O2S)0 50 intersects the monovariant curve in the area rich in the initial crystallization area of y(Ga2S3) is reflected in the liquidity. Based on Ga2S3 the eutectoid phase transition y(Ga2S3) ^ P(Ga2S3) occurs in the solid phase at 1200K temperature.
The binary crystallization m + a + y covers a wide range of concentrations in the phase diagrams of non-quasibinar sections. Thus, the possess kl begins on the upper curves, kl (kl ') ends on the lower curves. In the subsolidus of non-quasibinar sections, the a + P mixture precipitates at 300K temperature.
II
I
III IV
Fig. 5. Phase diagrams of non-quasibinary sections of Y2O2S-Ga2S3-Tb2O2S quasiternary system: I - Ga2S3-(Y2O2S)0.50(Tb2O2S)0.50(b), II - (Y2O2S)0.50(Tb2O2S)0.50-(Ga2S3)0.80(Tb2O2S)0.20(e2), III - Y2O2S-(Ga2S3)0.80(Tb2O2S)0.20(e2), IV - Tb2O2S-(Ga2S3)0.75(Y2O2S)0.25(a).
Thus, the above sections of the Y2O2S-Ga2S3-Tb2O2S quasi-triangular system are non-quasi-binary. Based on the initial components shown in the phase diagram, the a + P mixture precipitates at subsolidus at 300 K temperature, with the exception of solid solutions of limited viscosity.
Projection of the liquidus surface in the quasi-ternary system Y2O2S-Ga2S3-Tb2O2S.
The results of the study of quasibinar (lateral) and non-quasi-binary polythermic sections in quadrilateral systems Y2O2S-Ga2S3-Tb2O2S show the prognosis of the established liquidity surface (Figure 1 (d)), where the nature of the chemical interaction is relatively simple. Thus, the Ga2S3-Y2O2S and Ga2S3-Tb2O2S sides of a quasi-ternary system are quasi-binary eutectic systems with a limited solubility based on both components. On the Y2O2S-Tb2O2S side, a continuous solid solution area is formed. Thus, in the Y2O2S-Ga2S3-Tb2O2S quasi-ternary system, crystallization ends not at the nonvariant triple point, but at the
low-temperature binary nonvariant (where binary eutectic e1).
Quasibinar side (Ga2S3-Y2O2S, Ga2S3-Tb2O2S, Y2O2S-Tb2O2S) and non-quasibinar internal (Ga2S3-(Y2O2S)0.50(Tb2O2S)0.50,
(Y2O2S)0.50(Tb2O2S)0.50-(Ga2S3)0.80(Tb2O2S)0.20; Y2O2S-(Ga2S3)0.80(Tb2O2S)0.20 and Tb2O2S-(Ga2S3)0.75(Y2O2S)0.25) are studied by complex methods of physicochemical analysis. Based on the results obtained from the sections the projection of liquidus surface of the quasi-ternary system was constructed (Figure 6).The figure shows that in the projection of the liquidus surface, the monovariant equilibrium curves n1n2, e1e2 and n3n4: separate the four primary crystallization sites. Monovariant equilibrium curves are constructed according to the point of intersection of the initial crystallization curves in the corresponding sections. Its direction is extrapolated to the point of nonvariant equilibrium and the projection of the monovariant equilibrium curves drawn on the side of the solid triangle.
Fig. 6. Projection of the liquidus surface in the quasi-triangular system Y2O2S-Ga2S3-Tb2O2S: 1 - P [(Ga2Ss)1-x(Y2O2S)x-y(Tb2O2S)y]; 2. - y^Ss); 3 - a[(Y2O2S)1-x (Tb2O2S)x]; 4 - cfcO^-x (Tb2O2S)j1-y [(Ga2S3)x ]y
In the projection of the liquidus surface (Figure 6) a[(Y2O2S)i.x(Tb2O2S)x] the initial crystallization area (3) occupies a large area. It is in monovariant equilibrium with a solid solution of [(Y2O2S)i-x (Tb2O2S)x]i-y(Ga2S3)x along the n3n4 curve on the seat side of that density triangle.
On the vertex side of the density triangle Ga2S3, the a(Y2O2S)1-x (Tb2O2S)x area separates the e1e2 monovariant curve in the y(Ga2S3) field. y(Ga2S3) and above (Ga2S3)1-x(Y2O2S)x-y(Tb2O2S)y are in monovariant equilibrium on the n1n2 curve with a triple solid solution.
In the projection of the liquidus surface in the quasi-triangular system Y2O2S-Ga2S3-Tb2O2S, the isotherms were plotted by a graphical interpolation of 100K temperature. The isotherms determined by thermodynamic calculations are given by a broken line.
It should be noted that the nature of the chemical interaction in the studied polythermal sections is almost the same and confirms the parameters of the liquidus surface.
Based on the above, we can summarize our opinion that the projection of the liquidus surface of the quasi-triangular system Y2O2S-Ga2S3-Tb2O2S was established for the first time. It is clear from the projection that the nature of the chemical interaction in the system at equilibrium is relatively simple. Thus, since a continuous solid solution is formed on one side of the quasi-ternary system, the crystallization ends in a double nonvariant (e1) equilibrium. The observed three monovariant curves delimit four primary crystallization sites.
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Y2O2S-Ga2S3-Tb2O2S KVAZiUCLU SiSTEMiNDO FAZA TARAZLIGI
LB.Baxtiyarh, V.S.Mammadov, Z.M.Muxtarova, A.S.Abdullayeva
Y2O2S-Ga2S3-Tb2O2S kvaziuglu sistemlarda kvazibinar (yan) va qeyri- kvazibinar politermik kasiklarin tadqiqindan alinan naticalar qurulan likvidus sathinin proyeksiyasi gostarir ki, burada kimyavi qar§iliqh tasir xarakteri nisbatan sadadir. Bela ki, kvaziuglu sistemin Ga2S3-Y2O2S va Ga2S3-Tb2O2S taraflari har iki komponent asasinda mahdud qatiliqda hallolma olan kvazibinar evtektik sistemdir. Y2O2S-Tb2O2S tarafinda fasilasiz bark mahlul sahasi amala galir. Demali Y2O2S-Ga2S3-Tb2O2S kvaziuglu sisteminda kristalla§ma nonvariant uglu noqtada yox, a§agi temperaturlu ikili nonvariant (burada ikili evtektika el) noqtasinda qurtanr.
Agar sozlzr: lantanoid oksisulfidhri,sistemin komponentbri, kvaziuglu sistem, monovariant, nonvariant, evtektika, peritektika.
ФАЗОВОЕ РАВНОВЕСИЕ В КВАЗИТРЕУГОЛЬНОЙ СИСТЕМЕ Y2O2S-Ga2S3-Tb2O2S
И.Б.Бахтиярлы, В.С.Мамедов, З.М.Мухтарова, А.С.Абдуллаева
Результаты исследования квазибинарных и неквазибинарных политермических разрезов в квазитройных системах Y2O2S-Ga2S3-Tb2O2S показывают установившейся проекцию поверхности ликвидуса, где характер химического взаимодействия относительно прост. Таким образом, стороны квазитройной системы Ga2S3-Y2O2S и Ga2S3-Tb2O2S на основе обоих компонентов представляют собой квазибинарные эвтектические системы с ограниченной растворимостью. На стороне Y2O2S-Tb2O2S образуется сплошная область твердого раствора. Следовательно, в квазитройной системе Y2O2S-Ga2S3-Tb2O2S кристаллизация заканчивается не в нонвариантной тройной точке, а в низкотемпературной бинарной нонвариантной точке (где ei-бинарная эвтектика).
Ключевые слова: оксисульфиды лантаноидов, компоненты системы, квазитройная система, моновариант, нонвариант, эвтектика, перитектика.
