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CHEMICAL PROBLEMS 2019 no. 3 (17) ISSN 2221-8688
403
UDC 546.87 24 + 662724
RESEARCH INTO PHASE FORMATION AND SOME PHYSICAL AND CHEMICAL PROPERTIES OF THE Sb2Se3-GaSe SYSTEM ALLOYS
I.I. Aliyev1, N.A. Mammadova1, F.M. Sadigov2
1 Acad. M.Nagiyev Institute of Catalysis and Inorganic Chemistry of ANAS, 113,H. JavidAve., AZ1043, Baku, Azerbaijan; e-mail: [email protected]
2Baku State University 23, Z.Khalilov str., AZ-1148 Baku, Azerbaijan
Received 28.04.2019
Abstract: Behavior of interaction in the Sb2Se3-GaSe system was explored and a phase diagram constructed using the complex methods of physical and chemical analysis: differential thermal (DTA), X-ray phase (XRD), microstructural analysis (MSA), as well as the measurement of micro hardness and density. It found that in the system Sb2Se3-GaSe two congruently melting compounds of the GaSb4Se7 and GaSb2Se4 compositions are formed at 515 ° C and 490 ° C, respectively. It revealed that the GaSe-based solubility in solid state is 4 mol. % Sb2Se3;but if based on Sb2Se3 - it is 5 mol. % GaSe. Three eutectics are formed in the system with composition appropriate of 43 and 60 mol. % Sb2Se3 and melts at 470, 425 and 450°C, respectively.
Keywords: system, congruent, eutectic, solidus, liquidus. DOI: 10.32737/2221-8688-2019-3-403-407
It is known that chalcogenides of III B subgroup elements, as well as multicomponent phases on their basis are reputed to be perspective substances used in the development of photoelectric devices [1-3].
In literature [4-7], it is known that chancogenides of antimony Sb2X3(X-S,Se,Te) and solid solutions on their basis are used as materials for a p-branch of thermoelectric coolers. From this standpoint, the study of interaction between chalcogenides Sb2Se3 and GaSe is of scientific and practical significance. In literature [8-10] some systems were studied using chalcogenides of antimony.
The objective of the work is to study the phase formation and some physical and
chemical properties of Sb2Se3-GaSe system alloys.
Note that the Sb2Se3 compound is obtained with open for maximums and melts congruently at 617oC, crystallized in a rhombic syngony with lattice parameters: a= 11,633; b= 11,780; c= 3,985 A , space group Pbnm-D2h16 density p= 5,843 g/cm3 and micro hardness H^= 1200 MPa [11].
Gallium monoselenide GaSe melts congruently at 960oC and is crystallized in a hexagonal syngony with lattice parameters: a = 3,755; c = 15,94 A, Z=4, space group P63/mmc-D46h, density p = 5,03 g/cm3 and micro hardness 300 MPa [12].
Experimental part
Initial components of the Sb2Se3-GaSe system were synthesized by melting elements of high purity in quartz ampoules vacuumed up to 0.133 Pa at 700-1100°C. Note that antimony Sb-000, selenium -B4 and gallium 99.999% were used as initial elements. To obtain equilibrium state, alloys were annealed at 400oC for 350 hrs.
Equilibrium alloys were studied in line with methods of differential and thermal (DTA), X-ray phase, microstructural (MSA) analyses, as well as measurement of micro hardness and determination of density.
DTA of alloys of the system was conducted using «TEMASKON-2» with a heating rate of 10 deg./min. Calibration
chrome-aluminum thermocouple are used, AI2O3 is served as a standard. X-ray phase analysis was conducted on D2 PHASER using CuKa-radiation, Ni-filter. MSA of alloys of the system was investigated through the use of a metallographic microscope MIM-8 with GOI paste polished specimens. The microstructure was revealed
by an etchant with the HNO3 (conc) composition: H2O2 =1 : 1. ehe etching time was 20 sec.
Micro hardness of alloys of the system was measured using PMT-3 at loads of 0.10 and 0.20 N. Density of alloys of the system was determined using pycnometer method while toluene was used as a working liquid.
Results and discussion
Alloys of system Sb2Se3-GaSe are obtained in the form of light grey compact ingots. Resistance to air, water and organic solvents was studied. Strong mineral acids (HCl, HNO3) decompose them well.
Thermal analysis of the Sb2Se3-GaSe system alloys shows that two endothermic effects relating to solidus and liquidus were found on thermograms of alloys.
During studying microstructure of alloys of the system it found that on the basis of initial components there are limited areas of homogeneity. To determine areas of solid solutions on the basis of Sb2Se3, alloys containing 2, 5, 7 and 10 mol% GaSe were synthesized. Obtained alloys were annealed for 520 hrs. at 200 and 300°C and hardened in icy water. Then microstructural analysis was conducted. It revealed that the solubility on the basis of Sb2Se3 at room temperature is 5 mol
% GaSe, but at 470°C it is 10 % GaSe. Solid solutions on the basis of GaSe stretch up to 4 mol % GaSe.
Two compounds of the GaSb4Se7 and GaSb2Se4 compositions congruently melting at 515 and 490 C are formed in the system Sb2Se3-GaSe. The existence of compounds was confirmed using DTA, X-ray phase analysis, MSA analysis methods, microhardness and density measurements.
On thermo-grams of GaSb4Se7 and GaSb2Se4 compounds there is a single endothermic effect at 515 and 490°C which indicates their congruent melting. Figure 1 shows microstructure of alloys of eutectics, compounds GaSb4Se7 and GaSb2Se4. Microstructure (fig. 1 and c) of compounds GaSb4Se7 and GaSb2Se4 was studied after annealing for 750 hrs. at 450°C.
If
I
M W s
I v,
ITvr \ r
Fig.1. Microstructure of eutectics (a) and GaSb4Se7 (b) and GaSb2Se4 (c) compounds. a) -15 mol. % GaSe (eutectics), b)- GaSb4Se7, c)- GaSb2Se4.
According to X-ray phase analysis, inter-planar distances and intensities of diffraction peaks of initial alloys 20; 33,33; 50 and 70 mol. % GaSe (Fig.2) were calculated. It
found that diffraction peaks of alloys 33.33; 50 mol % GaSe revealed on diffraction pattern differ from diffraction peaks of initial compounds.
. I J, J 1 GaSe
. .......-r- -..—A-Jl ,.,,.„. .A., i GaSb2Se4 3
-... , * 1-1 . Jl ) ul GaSb4Se7 2 LiAXjiwd*^ i.......
0 -0" 0-1...... ......ul........j.....' 1 1 Jj 1 .......1.........1.........1........ 1.....
9fl
Fig.2. Diffractograms of alloys of the system Sb2Se3-GaSe. 1- Sb2Se3 2-20, 3- 33,33 (GaSb4Sey), 4- 50 (GaSb2Se4), 5-70 , 6- 100 mol. % GaSe.
t,oC 1000
900
800
700
600
500
400
300
200
960
Sb2Se3
GaSe
Fig. 3. Phase diagram of the Sb2Se3-GaSe system.
According to physical and chemical analysis, the state diagram of the Sb2Se3-GaSe system was constructed (Fig. 3). Part of liquidus in the concentration range of 0-20 mol % GaSe corresponds to primary separation of a-phase (solid solutions based on Sb2Se3), concentration limits of 20-43 mol % GaSe crystals of new phase GaSb4Se7 are separated
from liquid, primary crystallization of the phase GaSb2Se4 occurs in the range of 43-60 mol % GaSe, finally, P-phases (solid solutions based on GaSe) are crystallized in concentration range of 60-100 mol % GaSe .
It should be added that microhardness of alloys in the system was measured using PMT-3 loaded up to 0.15 N. Results of micro
hardness measurement of alloys are cited in Table to show that four rows of values are found in the system. For the a-phase, the microhardness varies within (1200-1250) MPa. In the concentration range of 20-43 mol. % GaSe a new value of microhardness (13501400) MPa is revealed to indicate the
microhardness of the new phase GaSb4Se7. In the range of 43-60 mol. % GaSe the microhardness value (1500-1530) MPa is in accord with the new GaSb2Se4 phase. For the GaSe compound, the microhardness values are 300 MPa.
Table. Results of DTA, measurement of micro hardness and density of the Sb2Se3-GaSe
system alloys
Composition, mol % Thermal effects, °C Density, 103kg/m3 Micro hardness of phases, MPa
Sb2Se3 GaSe a GaSb4Sev GaSb2Se4 ß
P=0.15 H
100 0.0 617 5.84 1200 - - -
97 3.0 560,610 5.82 1230 - - -
95 5.0 520,590 5.80 1250 - - -
90 10 470,565 5.74 1250 - - -
85 15 470,520 5.68 - - - -
80 20 570 5.65 Eutec. Eutec. - -
75 25 470,500 5.64 - - - -
70 30 470,510 5.60 - 1350 - -
66,6 33.3 515 5.63 - 1400 - -
60 40 425,480 5.55 - 1400 - -
57 43 425 5.50 - Eutec. Eutec. -
50 50 490 5.52 - - 1500 -
45 55 450,475 5.41 - 1530 -
40 60 450 5.35 - - Eutec. Eutec.
30 70 450,655 5.23 - - - 370
20 80 450,770 5.19 - - - 370
10 90 450,875 5.16 - - - 370
5,0 95 580,940 5.12 - - - 370
3,0 97 700,945 5.08 - - - 350
0,0 100 960 5.03 - - - 300
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SbSe3-GaSe SiSTEMiNDd FAZAOMOLOGOLMd УЭ ORÍNTÍLORÍN FÍZÍKÍ-KÍMYdVÍXASSBLdRÍMN T3DQÍQÍ
Í.Í. dliyev1, N.A. M3mm3dova1, F.M. Sadiqov2
1AMEA-nin acad. M.Nagiyev ad. Kataliz va Qeyri-Üzvi Kimya institutu AZ1043, Baki, H. Cavidpr.113; e-mail: aliyevimir@rambler. ru 2Baki Dovlat Universiteti AZ-1148 Baku, Z.Xalilov кид, 23
Fiziki-kimyavi analizin kompleks metodlari: diferensial-termiki (DTA), rentgenfaza (RFA), mikroqurulu§ (MQA) analizi va elaca da mikrobarkliyin va sixligin tayini vasitasila Sb2Se3-GaSe sistemi tadqiq edilmi§ va faza diaqrami qurulmu§dur. Müayyan edilmi§dir ki, Sb2Se3-GaSe sisteminda iki - GaSb4Se7 va GaSb2Se4 tarkibli uygun olaraq, 515оС va 490oC-da konqruyent ariyan birla§malar alinmi§dir. Sistemda GaSe asasinda 4 mol % Sb2Se3 hall oldugu halda, Sb2Se3 birla§masi asasinda isa 5 mol % GaSe hall oldugu a§kar edilmi§dir. Sistemda amala galan üg evtektikanin tarkibi 20; 43 и 60 mol % Sb2Se3, temperaturlari isa uygun olaraq 470, 425 и 450oC-dir. Agar sozfor: sistem, konqruyent, evtektika, solidus, likvidus.
ИССЛЕДОВАНИЕ ФАЗООБРАЗОВАНИЯ И НЕКОТОРЫХ ФИЗИКО-ХИМИЧЕСКИХ СВОЙСТВ СПЛАВОВ СИСТЕМЫ Sb2Se3-GaSe
И.И. Алиев1, Н.А. Мамедова1, Ф.М. Садыгов2
1 Институт катализа и неорганической химии Национальной АН Азербайджана AZ1043 Баку, пр.Г.Джавида,113; e-mail: aliyevimir@rambler. ru 2Бакинский государственный университет AZ-1148 Баку, у. З. Халилова, 23
Комплексными методами физико-химического анализа: дифференциально-термического (ДТА), рентгенофазового (РФА), микроструктурного (МСА) анализа, а также измерением микротвердости и плотности изучен характер взаимодействия в системе Sb2Se3-GaSe и построена фазовая диаграмма. Установлено, что в системе Sb2Se3-GaSe образуются два конгруэнтно плавящихся соединения GaSb4Se7 и GaSb2Se4 при температурах 515оС и 490оС соответственно. Установлено, что растворимость на основе GaSe в твердом состоянии составляет 4 мол. % Sb2Se3, а на основе Sb2Se3 -5 мол. % GaSe. В системе образуются три эвтектики, состав которых отвечает 20; 43 и 60 мол. % Sb2Se3 при температурах 470, 425 и 450оС соответственно.
Ключевые слова: система, конгруэнтный, эвтектика, солидус, ликвидус.
