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CHEMICAL PROBLEMS 2019 no. 2 (17) ISSN 2221-8688
291
UOT 546. 657/19/24+657/24
PHASE EQULIBRIA IN THE NdAs2Se4-Nd2Se3 SYSTEM
A.Q. Khudiyeva1, T.M.Ilyasli1, I.I.Aliyev2, S.A.Mehdiyeva2
1Baku State University, e-mail aynur. khudiyeva@yahoo.com 2Acad. M.F. Nagiyev Institute of Catalysis and Inorganic Chemistry National Academy of Sciences of Azerbaijan Baku, G. Javid ave. 113, e-mail: aliyevimir@rambler. ru
Received 23.04.2019
Abstract: The NdAs2Se4-Nd2Se3 system was investigated by methods of differential thermal (DTA), X-ray phase (XRF), microstructural (MSA) analysis, as well as microhardness and density measurements, and a T-x phase diagram was constructed. It has been established that this system is a non-quasi-binary section of the ternary Nd-As-Se system. Above the solidus temperature (6750C) the NdAs2Se4-Nd2Se3 system is not quasi-binary, and below the solidus is stable. In the NdAs2Se4-Nd2Se3 system solid solutions based on the initial components are practically not detected. Keywords: system, quasi-binary, solid solution, syngony, microhardness, density. DOI: 10.32737/2221-8688-2019-2-291-295
Introduction
Arsenic chalcogenides and related alloys have photoelectric, acoustic-optical properties [1-4]. As is known, rare-earth chalcogenides and ternary phases, as well as solid solutions obtained from them are also photoelectric, luminescent semiconductor materials with magnetic properties. These materials are widely used in various areas of the electronics industry [5-7].
From this point of view, it was interesting to investigate the physicochemical interaction of arsenic chalcogenides with neodymium chalcogenides. The search for new photosensitive and thermoelectric materials is both of scientific and practical importance. Earlier, we studied chemical interactions of
arsenic chalcogenides with rare-earth chalcogenides [8-10].
The purpose of the work is to study the phase equilibria and the construction of the phase diagram of the NdAs2Se4-Nd2Se3 system.
The Nd2Se3 compound melts congruently at 1700°C and is crystallized in a cubic system like Th3P4 with the unit cell parameters: a = 8.871 A, sp.gr. I43d-T6d, density p = 6.69 g/sm3 [11].
The NdAs2Se4 compound melts congruently at 675°C and is crystallized in a tetragonal system with lattice parameters: a = 12.62; c = 7.42 A, Z = 7, ppukn. = 5.75 g/sm3; px-
ray
= 5.99. g/sm3.
Experimental part
To study the phase equilibria in the NdAs2Se4-Nd2Se3 system, alloys were synthesized in a wide concentration range. The synthesis of ternary alloys of the system under consideration was carried out through fusing the NdAs2Se4 and Nd2Se3 components into quartz ampoules having been evacuated to 0.133 Pa at a temperature of 800-1200°C. To homogenize the alloys, annealing was performed at 450°C for 200 h. The alloys of the NdAs2Se4-Nd2Se3 system were studied by means of differential
thermal (DTA), X-ray phase (XRD), microstructural (MCA) analyses, and microhardness measurement and density determination.
DTA alloys of the system were carried out on a TERMOSKAN-2 device with an accuracy of 3-5°C, a chromel-alumel thermocouple, and calcined Al2O3 served as the standard. Heating rate of 9 degrees/min. X-ray phase analysis was performed on an X-ray instrument of the D2 PHASER model through the use of CuKa radiation with a Ni filter. The
micro-structural analysis of alloys was carried out using an MIM-8 microscope. In the study of alloy microstructure, an etchant of composition 1 N HNO3 + HF = 2:1 was used, the etching
time was 20 s. The microhardness of the phases was measured on a PMT-3 instrument with an accuracy of 5 %, and the density of the samples was determined by the pycnometric method.
Results and its discussion
Alloys of the NdAs2Se4-Nd2Se3 system in the concentration range 0-60 mol % Nd2Se3 are obtained in the form of compact ingots. Alloys in the range of 60-100 mol % Nd2Se3 are nonuniform. Therefore, in this range the samples were ground into powder at 200 atm. pressed into a tablet and exposed to heat treatment at 800°C for 100 hours.
The alloys of the NdAs2Se4-Nd2Se3 system in the form of ingots are resistant to air and water. Powdered samples are exposed to
hydrolysis with prolonged exposure to air. They are well soluble in nitric acid HNO3. Homogenized alloys were examined by methods of physical and chemical analysis. Note that the thermograms of the system alloys have three endothermic effects. Proceeding from the results of micro-structural analysis of alloys, it found that the alloys of the NdAs2Se4-Nd2Se3 system in the solid state are two-phased. In the system based on the initial components, solid solutions are not practically installed.
100 -t
g g t— <S> S î^i « M S g g s S; 53 = pi
1 .......... 1....... .......................... * i 1 ^ h <z> s S5 1 f [ J îltSJL
'1 [ ............"11 ..........* ■ " r ■ " si S cs^ CM 1 . SiJ s S «^î aim. g s S3 i j 11 m § S
..... 1 n i © = 4 f- 1 f—1 1 --_-J—I 1 1 ,.! V-l "i ■vr.- £11 1 ^ « •sO r- (N fsj -d- !P c-t nt, A,
Fig.1. Diffractograms of the alloys NdAs2Se4-Nd2Se3 system. 1- NdAs2Se4, 2- 30, 3-50, 4-70, 5-100 mol % Nd2Se3.
To confirm the results of differential thermal and micro-structural analysis, X-ray phase analysis of alloys with a content of 30, 50 and 70 mol % Nd2Se3 is required. On the basis of the experimentally calculated inter-planar
distances and line intensities, the initial compounds and intermediate alloys were compared. The results of radiographs of alloys containing 30, 50 and 70 mol % Nd2Se3 are shown in Fig. 1. As can be seen from Fig. 1, the
diffraction patterns of the alloys of the This indicates that the alloys of the system are NdAs2Se4-Nd2Se3 system consist of a mixture two-phased. of diffraction lines of the initial components.
Fig. 2. Phase diagram of the NdAs2Se4-Nd2Se3 system.
Thus, the x-ray analysis confirms the results of the DTA analysis and microstructure. Proceeding from the results of physicochemical analysis methods, the phase diagram of the NdAs2Se4-Nd2Se3 system was constructed (Fig.2). The NdAs2Se4 compound melts incongruently; therefore, above 675°C it decomposes by the reaction: NdAs2Se4 ^L + NdSe. The liquidus system consists of primary crystallization curves of the NdSe and Nd2Se3 compounds in the concentration range 0-30 mol % Nd2Se3 from the liquid stand primary crystals NdSe. In the range of 0-15 mol % Nd2Se3 during the secondary crystallization, three-phase regions are formed: (L+NdSe+NdAs2Se4). The starting crystals of the Nd2Se3 compound from the liquid are separated in the range of 30-100 mol. % Nd2Se3. Another three-phase region
(M+NdSe+Nd2Se3) was found in the range of 15-100 mol % Nd2Se3. In the system below, the solidus line, two-phase alloys (NdAs2Se4+Nd2Se3) crystallize. The NdAs2Se4-Nd2Se3 system intersects the mono-variant double eutectic lines at 900oC and the composition of 30 mol % Nd2Se3. The system undergoes peritectic transformation by the reaction: L+NdSe^ NdAs2Se4. Some physical-chemical properties of alloys of the NdAs2Se4-Nd2Se3 system are listed in Table. 1. From Table 1 it can be seen that two microhardness values are detected in the system. Of these, the first corresponds to the microhardness of NdAs2Se4 (1860-1870) MPa, and the value (2300-2340) MPa corresponds to the microhardness of Nd2Se3.
Table 1. Composition, results of DTA, measurements of microhardness and density determination
of alloys of the NdAs2Se4-N d2Se3 system.
Content, mol % Thermal effects, oC Density, q/sm3 Microhardness, MPa
NdAs2Se4 Nd2Se3 NdAs2Se4 Nd2Se3
Р=0.15 Н Р=0.20 Н
100 0,0 675, 1200 5,75 1860 -
95 5,0 510,650, 1190 5,80 1870 -
90 10 510,625, 1150 5,86 1870 -
85 15 510,1100 5,92 1860
80 20 510,720,1060 5,97 1860 -
70 30 510, 900 6,02 1860 -
60 40 510,900,1070 6,12 1860 -
50 50 510,900,1210 6,26 - -
40 60 510,900 6,30 - 2340
30 70 510,900 6,45 - 2340
20 80 510,900 6,55 - 2340
10 90 510,900 6,60 - 2340
5,0 95 510,900 6,64 - 2330
0,0 100 1700 6,69 - 2300
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11. Physico-chemical properties of
NdAs2Se4-Nd2Se3 SiSTEMiNDO FAZA TARAZLIGI
A.Q. Xudiyeva1, T.M.ilyasli1, LLdliyev2, S.A.Mehdiyeva2
1Baki Dovlst Universiteti AZ1148 Baki, Z.Xslilov kug., 23; e-mail:aynur.khudiyeva@yahoo.com 2AMEA -nin akad. M.Nagiyev adina Kataliz vs Qeyri-uzvi Kimya Institutu AZ 1143, Baki, H.Cavidpr., 113; e-mail: aliyevimir@,rambler. ru
Fiziki-kimysvi analiz (DTA, MQA, RFA, elscs ds mikrobsrkliyin vs sixligin tsyini) metodlari vasitssils NdAs2Se4-Nd2Se3 sisteminds faza tarazligi tsdqiq edilmi§ vs onun T-x faza diaqrami qurulmu§dur. Musyysn edilmi§dir ki, NdAs2Se4-Nd2Se3 sistemi Nd-As-Se uglu sisteminin qismsn qeyri-kvazibinar kssiyidir. Solidus temperaturundan yuxarida (675oC) NdAs2Se4-Nd2Se3 sistemi qeyri-kvazibinar, a§agida iss stabil kssik kimi ozunu gostsrir. NdAs2Se4-Nd2Se3 sisteminin ilkin komponentlsri ssasinda hsllolma sahssi praktiki olaraq tsyin edilmsmi§dir. Agar sozlw. sistem, qeyri-kvazibinar, bsrk mshlul, sinqoniya, mikrobsrklik, sixliq
ФАЗОВЫЕ РАВНОВЕСИЯ В СИСТЕМЕ mAs2Se4-NdSe3
А.Г. Худиева1, Т.М. Ильяслы1, И.И. Алиев2, С.А. Мехтиева2
1 Бакинский государственный университет AZ1148 Баку, ул. З.Халилова, 23; e-mail:aynur.khudiyeva@yahoo.com 2Институт катализа и неорганической химии им. акад. М.Нагиева Национальной АН Азербайджана AZ1143 Баку, пр.Г.Джавида, 113; e-mail: alive vimirarambler. ru
Методами физико-химического анализа (ДТА, РФА, МСА а также определением плотности и измерением микротвердости) исследовано фазовое равновесие и построена Т-х диаграмма системы NdAs2Se4-Nd2Se3. Установлено, что разрез NdAs2Se4-Nd2Se3. является неквазибинарным сечением тройной системы Nd-As-Se. Выше температуры солидуса (675oC) система NdAs2Se4-Nd2Se3 является неквазибинарной, а ниже линии солидуса система стабильна. В системе NdAs2Se4-Nd2Se3 на основе исходных компонентов твердые растворы практически не обнаружены.
Ключевые слова: система, неквазибинарный, твердый раствор, сингонии, микротвердость, плотность.
