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8CHEMIA | ХИМИЧЕСКИЕ НАУКИ
INTERACTIONS ALONG THE Bi Se-TmSe, AND Bi Se-Tm Se, JOINS OF THE
2 3 2 3 2 3 3 4J
Tm-Bi-Se TERNARY SYSTEM
F.M.Sadigov
doctor of chemical sciences, professor, General and Inorganic Chemistry
Baku State University Z.i.ismayilov dosent, General and Inorganic Chemistry Baku State University S.M.Mamedova assistant, General and Inorganic Chemistry Baku State University Y.K.Djafarova assistant, General and Inorganic Chemistry Baku State University
Садыгов Фуад Микайл, доктор химических наук, профессор кафедры Общей и неорганической химии, Бакинский Государственный Университет
Исмаилов Закир Ислам, доцент, кафедры Общей и неорганической химии, Бакинский Государственный Университет
Мамедова Саба Гусейнхан, ассистент, кафедры Общей и неорганической химии, Бакинский Государственный Университет
Джафарова Екана Керим, ассистент, кафедры Общей и неорганической химии, Бакинский Государственный Университет
ABSTRACT
Bi2Se3 - Tm2Se3 and Bi2Se3-Tm3Se4 joins are studied by physicochemical analysis. Both are quasi-binary sections of the Tm-BiSe ternary System. The ternary compound of TmBiSe3 composition is formed by a peritectic reaction in the Bi2Se3-Tm2Se3 join. Its solubility in Bi2Se3 at 300 K is 5 mol %.
АННОТАЦИЯ
Системы Bi2Se3 - Tm2Se3 и Bi2Se3-Tm3Se4 изучаются физико-химическим методом анализа. Оба квазибинарные сечения тройной системы Tm-Bi-Se. Тройное соединение состава TmBiSe3 формируется перитектической реакцией присоединения в системе Bi2Se3-Tm2Se3. Его растворимость в Bi2Se3 при 300 К составляет 5% мол.
Keywords: physicochemical analysis, quasi-binary, peritectic, microhardness,
Ключевые слова: физико-химический анализ, квазибинар, перитектика, микротвердость,
To elucidate the character of chemical interactions of experiment was carried out on a NTR-73 pyrometer in components in the Tm-Bi-Se ternary system, the Bi2Se3 - evacuated (10 -1 Pa) silica glass ampules. The high-temperature Tm2Se3 and Bi2Se3-Tm3Se4 joins were studied. parts of the liquidus were studied on a VDTA-8 thermal
The orthorhombic crystals of Bi2Se3 belong to the analyzer in graphite crucibles. X-ray diffraction patterns were tetradymite type. This compound is a semiconductor with the measured on a DRON-3 diffractometer (CuKa radiation). bandgap AE= 0.35 eV and lattice conductivity 0.025 W/(cm Microhardness was measured on a PMT-3 tester under 0.02 N K) at room temperature. The Seebeck coefficient for Bi2Se3 is loads. For microstructure examination, alloy laps were etched usually negative; the conductivity is 2000 S/cm [1, 2]. The cubic with dilute nitric acid (1:1). Microstructure examination crystals of Tm2Se3 are the Th3P4 type (a=8.59 A). The trigonal showed that Bi2Se3-Tm2Se3 and Bi2Se3-Tm3Se4 alloys containing crystals of a-Tm3Se4 are the CaHo2Se4 type (a=6.89 A). 0, 5, and 50 mol % Tm2Se3 and 0, 5 mol % Te3Se4 consist of one
Tm2Se3 and Tm3Se4 are semiconductors [3, 4]. phase; the others consist of two phases [5, 6].
Bismuth (B-4), selenium (22-4), and thulium metal (Tul-0) Microhardness measurements on Bi2Se3 - Tm2Se3 alloys were used for the syntheses of alloys. The alloys were prepared show three sets of values: 740 MPa for a light phase (Bi2Se3), by directly alloying the components in evacuated quartz 2100 MPa for a dark phase (TmBiSe3), and 3700 MPa for a ampoules at 1000 - 1200 K followed by slow cooling in the gray phase (Tm2Se3). On Bi2Se3 - Tm2Se4 alloys, two sets of turned off furnace. microhardness values were obtained, corresponding to Bi2Se3
For homogeneity, the as-synthesized alloys were additionally (740 MPa) and Tm3Se4 (3500 MPa). annealed for 350 h at a temperature 50-100 K lower than the On the bases of the above results, phase diagrams were solidus temperature. plotted for the Bi2Se3 - Tm2Se3 and Bi2Se3 - Tm3Se4 systems.
The resulting samples were studied by differential thermal The Bi2Se3 - Tm2Se3 system (Fig.1) is quasi-binary. The analysis (DTA), microstructure examination, X-ray powder ternary compound TmBiSe3 is formed at 1020 K at the 1:1 ratio diffraction, and by microhardness measurements. A DTA of the initial components by the peritectic reaction:
L + Tm„Se^+TmBiSe3
Bi2Ses
Tm^Se^
Fig.1. Phase diagram for the Bi2Se3-Tm2Se3 system.
The compound TmBiSe3 forms a eutectic, containing 15 mol % of Tm2Se3, with the a solid solution on the basis of Bi2Se3; the eutectic melts at 955 K. The Tm2Se3 solubility in Bi2Se3 at room temperature is 5 mol%.
Indexing X-ray powder diffraction patterns for TmBiSe3 shows that the crystals are orthorhombic with the structure
of the Sb2S3 type. The unit cell parameters are a=11.62 A, b=11.7lA, c=4.04A. Interlayer distances, hkl, and peak intensities for TmBiSe3 are given in the table.
The Bi2Se3 - Tm3Se4 system (Fig.2) is quasi-binary of the eutectic type. The eutectics contains 65 mol % Bi2Se3 and melts at 895 K.
Bi2Se3 20
Fig.2. Phase diagram for the Bi2Se3-Tm3Se4 system.
The Tm3Se4 solubility in Bi2Se3 is ca. 5 mol % at 300 K. To determine the boundary of Bi2Se3-based solid solutions, samples with compositions near Bi2Se3 were synthesized in 1-mol % intervals and homogenated by annealing at selected
temperatures.
Microstructure examinations on these alloys showed that the Tm2Se3 (Tm3Se4) solubility increases to 10 mol % from room temperature to the eutectic temperature.
X-ray diffraction data for TmBiSe3
I,% dexp, Â hkl dcalc, Â
15 8,232 110 8,243
30 5,849 020 5,855
28 5,232 120 5,228
10 4,132 220 4,124
25 3,694 130 3,701
88 3,201 121 3,197
62 3,190 211 3,191
100 2,880 221 2,886
48 2,788 301 2,796
75 2,620 240 2,614
25 2,534 231 2,528
28 2,380 041 2,371
10 2,328 430 2,336
20 2,192 421 2,188
30 2,011 002 2,021
20 1,942 600 1,936
25 1,790 132 1,792
15 1,726 232 1,732
28 1,616 720 1,624
20 1,526 271 1,532
10 1,424 37l 1,428
Comparing the results of studying the Bi2Se3-Tm2Se3 and Bi2Se3-Tm3Se4 joins with the data for the Bi2Se3-Sm2Se3 and Bi2Se3-Sm3Se4 joins, we may infer that the characters of interactions are similar. This seems to be caused by the similarity of the electronic structures of lanthanides [7, 8].
The joins are quasi-binary with narrow fields of solid solubility in Bi2Se3.
The systems Bi2Se3-Sm2Se3 and Bi2Se3-Tm2Se3 each form one ternary compound of the Sm (Tm)BiSe3 composition.
REFERENCES
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