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Phase relations in the Tl2S–Tl5Se2Br–TlBr ternary system
Journal of Alloys and Compounds 353 (2003) 180–183
L
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Phase relations in the Tl 2 S–Tl 5 Se 2 Br–TlBr ternary system I.E. Barchij*, E.Yu. Peresh, N.J. Haborets, M.Yu. Sabov, V.V. Tzigika Department of Chemistry, Uzhgorod National University, Pidgirna str.46, 88000, Uzhgorod, Ukraine Received 26 September 2001; received in revised form 30 September 2002; accepted 30 September 2002
Abstract The Tl 2 S–Tl 5 Se 2 Br–TlBr phase diagram was investigated by DTA and X-ray methods. Three vertical sections, a liquidus projection and a perspective representation of the phase diagram were constructed. The liquidus of this system consists of four fields of primary crystallization. The one-, two- and three-phase spaces which form the Tl 2 S–Tl 5 Se 2 Br–TlBr ternary system are described. 2002 Elsevier Science B.V. All rights reserved. Keywords: Crystal structures; Phase diagram; Thermal analysis; X-ray diffraction; Semiconductors
1. Introduction The quasiternary Tl 2 S–Tl 5 Se 2 Br–TlBr system is of interest because of the presence of binary and ternary compounds which reveal semiconductor properties and have a wide practical application. Tl 2 S, Tl 2 Se and TlBr melt congruently at 725 [1], 663 [2,3] and 733 K [4], respectively. One polymorphous modification crystallizing with rhombohedric symmetry exists for Tl 2 S (parameters a51.220, c51.817 nm, space group R3¯ ) [1]. Tl 2 Se is also known in one modification— tetragonal structure type (space group P4 /n) with lattice parameters of a50.852, c51.268 nm, c /a51.40, d58.12 g / sm 3 and Z510 [2,3]. According to Ref. [4] TlBr crystallizes in a cubic structure (NaCl structure type, space group Fm3 m, a50.658 nm).
three-phase equilibria, a eutectic at 63 mol.% Tl 2 S (690 K) and a peritectic one at 47 mol.% Tl 2 S (716 K).
2.2. Tl2 Se–TlBr quasibinary system Tl 5 Se 2 Br is formed in the Tl 2 Se–TlBr system and melts congruently at 746 K [7,8]. The curves of the Tl 2 Se and Tl 5 Se 2 Br primary crystallization cross in the eutectic point with the coordinates 90 mol.% Tl 2 Se and 715 K. Tl 2 Se and Tl 5 Se 2 Br form a limited solid solution region (in the 75–100 mol.% Tl 2 Se concentration range), which decomposes peritectically at 718 K. According to [7], Tl 5 Se 2 Br crystallizes with tetragonal symmetry, space group I4 /mcm and lattice parameters of a50.86083, c5 1.29205 nm.
2.3. Tl2 S–Tl2 Se quasibinary system 2. Bibliographic data of the quasibinary systems
2.1. Tl2 S–TlBr quasibinary system The phase diagram of the Tl 2 S–TlBr system, which was investigated by Blachnik and Dreisbach [5,6], is characterized by the formation of Tl 6 SBr 4 which melts incongruently. The peritectic reaction L1TlBr⇔Tl 6 SBr 4 takes place at 716 K. This ternary compound makes a polymorphous transition according to the results of DTA analyses. Tl 2 S, TlBr and Tl 6 SBr 4 liquidus curves are characterized by *Corresponding author.
The character of the Tl 2 S–Tl 2 Se system was investigated by Slobodijan et al. [9]. On the basis of DTA and X-ray results the phase diagram was plotted (Fig. 1). The liquidus of this system consists of two curves of primary crystallization of the Tl 2 S and Tl 2 Se compounds. The solidus part is represented by a field of secondary crystallization of the binary eutectic L⇔Tl 2 S1Tl 2 Se. The coordinates of the eutectic point are 65 mol.% Tl 2 Se and 590 K. X-ray studies revealed that there are limited solid solution regions of Tl 2 S (a-phase) and the Tl 2 Se (bphase), extending to 10 mol.% at the eutectic temperature. The solubility decreases with decreasing temperature and
0925-8388 / 02 / $ – see front matter 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0925-8388(02)01137-4
I.E. Barchij et al. / Journal of Alloys and Compounds 353 (2003) 180–183
Fig. 1. Phase diagram of the Tl 2 S–Tl 2 Se quasibinary system.
extends to 5 mol.% for the a-phase and to 10 mol.% for the b-phase at 423 K.
3. Experimental As educts we used thallium (I) sulfide, selenide, bromide and Tl 5 Se 2 Br. Synthesis of these compounds was carried out with high-purity elements (Tl: 99.997 wt.%, S: 99.9997 wt.%, Se: 99.9998 wt.%, Br: 99.9998 wt.%). Tl 2 S, Tl 2 Se and TlBr were prepared from stoichiometric amounts of the elements in evacuated quartz containers by annealing at 760 K (exposure at maximum temperature 24 h). After slow cooling homogenization took place at 423 K for 82–96 h. The binary compounds were purified by zone crystallization methods. The purity was controlled by chemical–spectral analysis with a quartz spectrograph (ISP-30). The purity of the initial components (containing Si, Fe, Mg, Al, Cd, Sn, Cu, Ag, Bi, Pb) were 2.1310 24 – 3.4310 25 wt.%. Identification of Tl 2 S, Tl 2 Se and TlBr was done by the DTA and X-ray analysis. Tl 5 Se 2 Br was obtained from Tl 2 Se and TlBr. Fifty-four alloys were prepared for the investigation of the Tl 2 S–Tl 5 Se 2 Br–TlBr system. Their compositions and
Fig. 2. Composition of the alloys in the Tl 2 S–Tl 2 Se–TlBr ternary system.
181
distribution on the concentration triangle are shown in Fig. 2. The composition of the alloys is given in mole percent of the initial components of the system. The highest synthesis temperature was 763 K. After thermal treatment at the highest temperature for 10–12 h, slow cooling (25–30 K / h) of the samples to 483 K took place. The alloys were homogenized for 168 h at this temperature and then quenched in cool water. The obtained alloys were investigated by differencethermal (NTR-62), X-ray phase (Dron-3m, CuKa radiation) analyses and mathematics modeling of phase equilibria by the simplex method [10,11].
4. Triangulation The Tl 2 S–Tl 2 Se–TlBr system (Fig. 3) can be divided into the separate subsystems Tl 2 S–Tl 5 Se 2 Br–TlBr (I) and Tl 2 S–Tl 2 Se–Tl 5 Se 2 Br (II) by the only quasibinary section Tl 2 S–Tl 5 Se 2 Br. The sides of the triangle are formed by the Tl 2 S–Tl 2 Se quasibinary system of eutectic type and two Tl 2 S–TlBr, Tl 2 Se–TlBr quasibinary systems, which are characterized by the formation of Tl 5 Se 2 Br (melts congruently) and of Tl 6 SBr 4 (melts incongruently). It is necessary to study the phase equilibria in both ternary subsystems for the profound investigation of the physicochemical interaction in the Tl 2 S–Tl 2 Se–TlBr system.
5. Tl 2 S–Tl 5 Se 2 Br–TlBr system
5.1. Tl2 S–Tl5 Se2 Br quasibinary system As shown in Fig. 4, the Tl 2 S–Tl 5 Se 2 Br system is of the eutectic type and is characterized by the primary crystallization curves of Tl 2 S and Tl 5 Se 2 Br which cross at the eutectic point with the coordinates: 16 mol.% Tl 5 Se 2 Br and 658 K. Phase relations are described by six phase regions: liquid, L, a, solid solution based on Tl 2 S, d, solid
Fig. 3. Triangulation of Tl 2 S–Tl 2 Se–TlBr ternary system.
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I.E. Barchij et al. / Journal of Alloys and Compounds 353 (2003) 180–183
Fig. 4. Phase diagram of the Tl 2 S–Tl 5 Se 2 Br quasibinary system.
solution based on Tl 5 Se 2 Br, and the two-phase regions L1a, L1d and a1d. The results of X-ray studies show that the solubility at the eutectic temperature extends to 10 mol.% at the Tl 2 S side and 38 mol.% at the Tl 5 Se 2 Br side. The solubility decreases with decreasing temperature and extends to 5 mol.% for Tl 2 S and to |15 mol.% for Tl 5 Se 2 Br at 423 K.
Fig. 6. Perspective representation of the Tl 2 S–Tl 5 Se 2 Br–Tl 6 SBr 4 secondary ternary system.
tem. Below 656 K all alloys are a mixture of solid Tl 6 SBr 4 and solid Tl 5 Se 2 Br.
5.3. Liquidus surface projection and perspective representation of the Tl2 S–Tl5 Se2 Br–TlBr ternary system 5.2. Tl6 SBr4 -Tl5 Se2 Br vertical section The Tl 6 SBr 4 –Tl 5 Se 2 Br vertical section (Fig. 5) crosses the primary crystallization fields of TlBr and Tl 5 Se 2 Br, which melt congruently. A decrease of the peritectic temperature from 716 to 656 K of Tl 6 SBr 4 is observed in the concentration region 0–35 mol.% Tl 5 Se 2 Br. The line b 1 –b 3 –k 2 –c 2 in the vertical section is special. It is characterised by the peritectic process L1g⇔d which passes with complete exhausting of the liquid (L) and solid phase (g) with formation of a new phase (s). The given peritectic process passes in an interval of temperatures, begins on a line b 1 –k 2 and comes to an end on a line b 1 –b 3 –k 2 –c 3 . Thermal effects at 656 K represent the peritectic P in the Tl 2 S–TlBr–Tl 5 Se 2 Br quasiternary sys-
Fig. 5. Phase diagram of the Tl 6 SBr 4 –Tl 5 Se 2 Br section.
The perspective view of the Tl 2 S–Tl 5 Se 2 Br–Tl 6 SBr 4 and Tl 6 SBr 4 –Tl 5 Se 2 Br–TlBr subsystems (Figs. 6 and 7) are plotted on the basis of the DTA and X-ray investigation of the samples of the Tl 2 S–TlBr–Tl 5 Se 2 Br systems and the data of Refs. [5–9] with a mathematical modeling of the liquidus surface by the simplex method. The liquidus of the Tl 2 S–Tl 5 Se 2 Br–Tl 6 SBr 4 ternary subsystem consists of four primary crystallization areas: A9e 2 Ee 4 A9–Tl 2 S (a-solid solution); B9p 1 Pk 1 B9–TlBr (gsolid solution); C9k 1 Pee 4 C9–Tl 5 Se 2 Br (d-solid solution) and p 1 e 2 EPp 1 –Tl 6 SBr 4 (s-solid solution) (Fig. 6). The liquidus of the Tl 6 SBr 4 –Tl 5 Se 2 Br–TlBr ternary subsystem
Fig. 7. Perspective representation of the Tl 6 SBr 4 –Tl 5 Se 2 Br–TlBr secondary ternary system.
I.E. Barchij et al. / Journal of Alloys and Compounds 353 (2003) 180–183
Fig. 8. Liquidus surface projection of the Tl 2 S–Tl 5 Se 2 Br–TlBr ternary system.
consists of two primary crystallization areas. The primary crystallization areas of TlBr (g-solid solution) and Tl 5 Se 2 Br (d-solid solution) are limited by the surfaces D9B9k 1 e 1 D9. The primary crystallization of the ternary is limited by the surface C9k 1 e 1 C9. The subsolidus parts of both systems consist of the mono- and multiphase areas of the components. The projection of the liquidus surface of the Tl 2 S– Tl 5 Se 2 Br–TlBr quasiternary system (Fig. 8) on the concentration triangle was first constructed according to the results of the present investigation. It consists of four fields of primary crystallization: Tl 2 S (a-solid solution), TlBr (g-solid solution), Tl 5 Se 2 Br (dsolid solution) and Tl 6 SBr 4 (s-solid solution). The a-solid solution is limited by the lines Tl 2 S–e 2 –E–e 3 , the g-solid solution by TlBr–p 1 –P–e 1 , the d-solid solution by Tl 5 Se 2 Br–e 1 –P–E–e 3 and the s-solid solution by p 1 –P– E–e 2 . The fields of primary crystallization are divided by five monovariant lines p 1 –P (the peritectic process L1
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TlBr⇔Tl 6 SBr 4 ), e 2 –E (eutectic process L⇔Tl 6 SBr 4 1 Tl 2 S), e 1 –E (eutectic process L⇔Tl 5 Se 2 Br1TlBr), e 3 –E (eutectic process L⇔Tl 5 Se 2 Br1Tl 2 S) and by six invariant points, four corresponding to binary invariant processes and two corresponding to ternary ones: L1 TlBr⇔Tl 6 SBr 4 1Tl 5 Se 2 Br (peritectic reaction in P point at 656 K) and L⇔Tl 5 Se 2 Br1Tl 2 S1Tl 6 SBr 4 (eutectic reaction in E point at 632 K). The types, temperatures and coordinates of the invariant processes in the Tl 2 S– Tl 5 Se 2 Br–TlBr ternary system are shown in Table 1. Points A9, B9, C9 and D9 which are on the edges of the triangles represent the melting temperatures of the corresponding components.
References [1] G.Z. Vinogradova, Glass-formation and Phase Equilibria in the Chalcogenides Systems, Nauka, Moscow, 1984, in Russian. [2] E.Yu. Turkina, G.M. Orlova, Izv. Akad. Nauk SSSR. Neorg. Mater. 28 (1983) 2113. [3] D.M. Chizikov, V.P. Schastliviy, Selenium and Selenides, Nauka, Moscow, 1964, in Russian. [4] K. Genchi, F. Kazuo, M. Takoshi, Chem. Lett. 9 (1972) 831. [5] R. Blachnik, H. Dreisbach, Z. Naturforsch. 36 (1981) 1500. [6] R. Blachnik, H. Dreisbach, J. Relzl, Mat. Res. Bull. 19 (1984) 599. [7] R. Blachnik, H. Dreisbach, J. Solid State Chem. 52 (1984) 53. [8] E.Yu.V.B. Peresh, V.V. Lazarev, O.I. Tzigika, E.A. Korneychuk, Izv. Akad. Nauk SSSR Neorg. Mater 27 (1991) 2079. [9] L.A. Slobodijan, I.E. Barchij, E.Yu. Peresh, M.Yu. Sabov, Visn. Uzhgorod Derzh. Univ. Ser. Khim. 3 (1998) 69. [10] V.B. Ufimtzev, A.A. Lobanov, Heterohenium Equilibria in the Technology of the Semiconductors Materials, Metallurgija, Moscow, 1981, in Russian. [11] I.E. Barchij, Ukr. Khim. Zh., in press.
Table 1 Types, temperatures and coordinates of the invariant processes in the Tl 2 S–Tl 5 Se 2 Br–TlBr ternary system Type
Binary Binary Binary Binary
Process
invariant invariant invariant invariant
eutectic eutectic eutectic peritectic
Ternary invariant eutectic Ternary invariant peritectic
e1 e2 e4 p1
(L⇔Tl 5 Se 2 Br1TlBr) (L⇔Tl 6 SeBr 4 1Tl 2 S) (L⇔Tl 5 Se 2 Br1Tl 2 S) (L1TlBr⇔Tl 6 SeBr 4 )
E 1 (L⇔Tl 5 Se 2 Br1Tl 2 S1Tl 6 SeBr 4 ) P (L1TlBr⇔Tl 6 SeBr 4 1Tl 5 Se 2 Br)
T (K)
Coordinates (mol.%) Tl 2 S
Tl 5 Se 2 Br
TlBr
705 690 658 716
– 63 84 47
15 – 16 –
85 37 – 53
632 656
53 41
17 16
30 43
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Phase relations in the Tl 2 S–Tl 5 Se 2 Br–TlBr ternary system I.E. Barchij*, E.Yu. Peresh, N.J. Haborets, M.Yu. Sabov, V.V. Tzigika Department of Chemistry, Uzhgorod National University, Pidgirna str.46, 88000, Uzhgorod, Ukraine Received 26 September 2001; received in revised form 30 September 2002; accepted 30 September 2002
Abstract The Tl 2 S–Tl 5 Se 2 Br–TlBr phase diagram was investigated by DTA and X-ray methods. Three vertical sections, a liquidus projection and a perspective representation of the phase diagram were constructed. The liquidus of this system consists of four fields of primary crystallization. The one-, two- and three-phase spaces which form the Tl 2 S–Tl 5 Se 2 Br–TlBr ternary system are described. 2002 Elsevier Science B.V. All rights reserved. Keywords: Crystal structures; Phase diagram; Thermal analysis; X-ray diffraction; Semiconductors
1. Introduction The quasiternary Tl 2 S–Tl 5 Se 2 Br–TlBr system is of interest because of the presence of binary and ternary compounds which reveal semiconductor properties and have a wide practical application. Tl 2 S, Tl 2 Se and TlBr melt congruently at 725 [1], 663 [2,3] and 733 K [4], respectively. One polymorphous modification crystallizing with rhombohedric symmetry exists for Tl 2 S (parameters a51.220, c51.817 nm, space group R3¯ ) [1]. Tl 2 Se is also known in one modification— tetragonal structure type (space group P4 /n) with lattice parameters of a50.852, c51.268 nm, c /a51.40, d58.12 g / sm 3 and Z510 [2,3]. According to Ref. [4] TlBr crystallizes in a cubic structure (NaCl structure type, space group Fm3 m, a50.658 nm).
three-phase equilibria, a eutectic at 63 mol.% Tl 2 S (690 K) and a peritectic one at 47 mol.% Tl 2 S (716 K).
2.2. Tl2 Se–TlBr quasibinary system Tl 5 Se 2 Br is formed in the Tl 2 Se–TlBr system and melts congruently at 746 K [7,8]. The curves of the Tl 2 Se and Tl 5 Se 2 Br primary crystallization cross in the eutectic point with the coordinates 90 mol.% Tl 2 Se and 715 K. Tl 2 Se and Tl 5 Se 2 Br form a limited solid solution region (in the 75–100 mol.% Tl 2 Se concentration range), which decomposes peritectically at 718 K. According to [7], Tl 5 Se 2 Br crystallizes with tetragonal symmetry, space group I4 /mcm and lattice parameters of a50.86083, c5 1.29205 nm.
2.3. Tl2 S–Tl2 Se quasibinary system 2. Bibliographic data of the quasibinary systems
2.1. Tl2 S–TlBr quasibinary system The phase diagram of the Tl 2 S–TlBr system, which was investigated by Blachnik and Dreisbach [5,6], is characterized by the formation of Tl 6 SBr 4 which melts incongruently. The peritectic reaction L1TlBr⇔Tl 6 SBr 4 takes place at 716 K. This ternary compound makes a polymorphous transition according to the results of DTA analyses. Tl 2 S, TlBr and Tl 6 SBr 4 liquidus curves are characterized by *Corresponding author.
The character of the Tl 2 S–Tl 2 Se system was investigated by Slobodijan et al. [9]. On the basis of DTA and X-ray results the phase diagram was plotted (Fig. 1). The liquidus of this system consists of two curves of primary crystallization of the Tl 2 S and Tl 2 Se compounds. The solidus part is represented by a field of secondary crystallization of the binary eutectic L⇔Tl 2 S1Tl 2 Se. The coordinates of the eutectic point are 65 mol.% Tl 2 Se and 590 K. X-ray studies revealed that there are limited solid solution regions of Tl 2 S (a-phase) and the Tl 2 Se (bphase), extending to 10 mol.% at the eutectic temperature. The solubility decreases with decreasing temperature and
0925-8388 / 02 / $ – see front matter 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0925-8388(02)01137-4
I.E. Barchij et al. / Journal of Alloys and Compounds 353 (2003) 180–183
Fig. 1. Phase diagram of the Tl 2 S–Tl 2 Se quasibinary system.
extends to 5 mol.% for the a-phase and to 10 mol.% for the b-phase at 423 K.
3. Experimental As educts we used thallium (I) sulfide, selenide, bromide and Tl 5 Se 2 Br. Synthesis of these compounds was carried out with high-purity elements (Tl: 99.997 wt.%, S: 99.9997 wt.%, Se: 99.9998 wt.%, Br: 99.9998 wt.%). Tl 2 S, Tl 2 Se and TlBr were prepared from stoichiometric amounts of the elements in evacuated quartz containers by annealing at 760 K (exposure at maximum temperature 24 h). After slow cooling homogenization took place at 423 K for 82–96 h. The binary compounds were purified by zone crystallization methods. The purity was controlled by chemical–spectral analysis with a quartz spectrograph (ISP-30). The purity of the initial components (containing Si, Fe, Mg, Al, Cd, Sn, Cu, Ag, Bi, Pb) were 2.1310 24 – 3.4310 25 wt.%. Identification of Tl 2 S, Tl 2 Se and TlBr was done by the DTA and X-ray analysis. Tl 5 Se 2 Br was obtained from Tl 2 Se and TlBr. Fifty-four alloys were prepared for the investigation of the Tl 2 S–Tl 5 Se 2 Br–TlBr system. Their compositions and
Fig. 2. Composition of the alloys in the Tl 2 S–Tl 2 Se–TlBr ternary system.
181
distribution on the concentration triangle are shown in Fig. 2. The composition of the alloys is given in mole percent of the initial components of the system. The highest synthesis temperature was 763 K. After thermal treatment at the highest temperature for 10–12 h, slow cooling (25–30 K / h) of the samples to 483 K took place. The alloys were homogenized for 168 h at this temperature and then quenched in cool water. The obtained alloys were investigated by differencethermal (NTR-62), X-ray phase (Dron-3m, CuKa radiation) analyses and mathematics modeling of phase equilibria by the simplex method [10,11].
4. Triangulation The Tl 2 S–Tl 2 Se–TlBr system (Fig. 3) can be divided into the separate subsystems Tl 2 S–Tl 5 Se 2 Br–TlBr (I) and Tl 2 S–Tl 2 Se–Tl 5 Se 2 Br (II) by the only quasibinary section Tl 2 S–Tl 5 Se 2 Br. The sides of the triangle are formed by the Tl 2 S–Tl 2 Se quasibinary system of eutectic type and two Tl 2 S–TlBr, Tl 2 Se–TlBr quasibinary systems, which are characterized by the formation of Tl 5 Se 2 Br (melts congruently) and of Tl 6 SBr 4 (melts incongruently). It is necessary to study the phase equilibria in both ternary subsystems for the profound investigation of the physicochemical interaction in the Tl 2 S–Tl 2 Se–TlBr system.
5. Tl 2 S–Tl 5 Se 2 Br–TlBr system
5.1. Tl2 S–Tl5 Se2 Br quasibinary system As shown in Fig. 4, the Tl 2 S–Tl 5 Se 2 Br system is of the eutectic type and is characterized by the primary crystallization curves of Tl 2 S and Tl 5 Se 2 Br which cross at the eutectic point with the coordinates: 16 mol.% Tl 5 Se 2 Br and 658 K. Phase relations are described by six phase regions: liquid, L, a, solid solution based on Tl 2 S, d, solid
Fig. 3. Triangulation of Tl 2 S–Tl 2 Se–TlBr ternary system.
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Fig. 4. Phase diagram of the Tl 2 S–Tl 5 Se 2 Br quasibinary system.
solution based on Tl 5 Se 2 Br, and the two-phase regions L1a, L1d and a1d. The results of X-ray studies show that the solubility at the eutectic temperature extends to 10 mol.% at the Tl 2 S side and 38 mol.% at the Tl 5 Se 2 Br side. The solubility decreases with decreasing temperature and extends to 5 mol.% for Tl 2 S and to |15 mol.% for Tl 5 Se 2 Br at 423 K.
Fig. 6. Perspective representation of the Tl 2 S–Tl 5 Se 2 Br–Tl 6 SBr 4 secondary ternary system.
tem. Below 656 K all alloys are a mixture of solid Tl 6 SBr 4 and solid Tl 5 Se 2 Br.
5.3. Liquidus surface projection and perspective representation of the Tl2 S–Tl5 Se2 Br–TlBr ternary system 5.2. Tl6 SBr4 -Tl5 Se2 Br vertical section The Tl 6 SBr 4 –Tl 5 Se 2 Br vertical section (Fig. 5) crosses the primary crystallization fields of TlBr and Tl 5 Se 2 Br, which melt congruently. A decrease of the peritectic temperature from 716 to 656 K of Tl 6 SBr 4 is observed in the concentration region 0–35 mol.% Tl 5 Se 2 Br. The line b 1 –b 3 –k 2 –c 2 in the vertical section is special. It is characterised by the peritectic process L1g⇔d which passes with complete exhausting of the liquid (L) and solid phase (g) with formation of a new phase (s). The given peritectic process passes in an interval of temperatures, begins on a line b 1 –k 2 and comes to an end on a line b 1 –b 3 –k 2 –c 3 . Thermal effects at 656 K represent the peritectic P in the Tl 2 S–TlBr–Tl 5 Se 2 Br quasiternary sys-
Fig. 5. Phase diagram of the Tl 6 SBr 4 –Tl 5 Se 2 Br section.
The perspective view of the Tl 2 S–Tl 5 Se 2 Br–Tl 6 SBr 4 and Tl 6 SBr 4 –Tl 5 Se 2 Br–TlBr subsystems (Figs. 6 and 7) are plotted on the basis of the DTA and X-ray investigation of the samples of the Tl 2 S–TlBr–Tl 5 Se 2 Br systems and the data of Refs. [5–9] with a mathematical modeling of the liquidus surface by the simplex method. The liquidus of the Tl 2 S–Tl 5 Se 2 Br–Tl 6 SBr 4 ternary subsystem consists of four primary crystallization areas: A9e 2 Ee 4 A9–Tl 2 S (a-solid solution); B9p 1 Pk 1 B9–TlBr (gsolid solution); C9k 1 Pee 4 C9–Tl 5 Se 2 Br (d-solid solution) and p 1 e 2 EPp 1 –Tl 6 SBr 4 (s-solid solution) (Fig. 6). The liquidus of the Tl 6 SBr 4 –Tl 5 Se 2 Br–TlBr ternary subsystem
Fig. 7. Perspective representation of the Tl 6 SBr 4 –Tl 5 Se 2 Br–TlBr secondary ternary system.
I.E. Barchij et al. / Journal of Alloys and Compounds 353 (2003) 180–183
Fig. 8. Liquidus surface projection of the Tl 2 S–Tl 5 Se 2 Br–TlBr ternary system.
consists of two primary crystallization areas. The primary crystallization areas of TlBr (g-solid solution) and Tl 5 Se 2 Br (d-solid solution) are limited by the surfaces D9B9k 1 e 1 D9. The primary crystallization of the ternary is limited by the surface C9k 1 e 1 C9. The subsolidus parts of both systems consist of the mono- and multiphase areas of the components. The projection of the liquidus surface of the Tl 2 S– Tl 5 Se 2 Br–TlBr quasiternary system (Fig. 8) on the concentration triangle was first constructed according to the results of the present investigation. It consists of four fields of primary crystallization: Tl 2 S (a-solid solution), TlBr (g-solid solution), Tl 5 Se 2 Br (dsolid solution) and Tl 6 SBr 4 (s-solid solution). The a-solid solution is limited by the lines Tl 2 S–e 2 –E–e 3 , the g-solid solution by TlBr–p 1 –P–e 1 , the d-solid solution by Tl 5 Se 2 Br–e 1 –P–E–e 3 and the s-solid solution by p 1 –P– E–e 2 . The fields of primary crystallization are divided by five monovariant lines p 1 –P (the peritectic process L1
183
TlBr⇔Tl 6 SBr 4 ), e 2 –E (eutectic process L⇔Tl 6 SBr 4 1 Tl 2 S), e 1 –E (eutectic process L⇔Tl 5 Se 2 Br1TlBr), e 3 –E (eutectic process L⇔Tl 5 Se 2 Br1Tl 2 S) and by six invariant points, four corresponding to binary invariant processes and two corresponding to ternary ones: L1 TlBr⇔Tl 6 SBr 4 1Tl 5 Se 2 Br (peritectic reaction in P point at 656 K) and L⇔Tl 5 Se 2 Br1Tl 2 S1Tl 6 SBr 4 (eutectic reaction in E point at 632 K). The types, temperatures and coordinates of the invariant processes in the Tl 2 S– Tl 5 Se 2 Br–TlBr ternary system are shown in Table 1. Points A9, B9, C9 and D9 which are on the edges of the triangles represent the melting temperatures of the corresponding components.
References [1] G.Z. Vinogradova, Glass-formation and Phase Equilibria in the Chalcogenides Systems, Nauka, Moscow, 1984, in Russian. [2] E.Yu. Turkina, G.M. Orlova, Izv. Akad. Nauk SSSR. Neorg. Mater. 28 (1983) 2113. [3] D.M. Chizikov, V.P. Schastliviy, Selenium and Selenides, Nauka, Moscow, 1964, in Russian. [4] K. Genchi, F. Kazuo, M. Takoshi, Chem. Lett. 9 (1972) 831. [5] R. Blachnik, H. Dreisbach, Z. Naturforsch. 36 (1981) 1500. [6] R. Blachnik, H. Dreisbach, J. Relzl, Mat. Res. Bull. 19 (1984) 599. [7] R. Blachnik, H. Dreisbach, J. Solid State Chem. 52 (1984) 53. [8] E.Yu.V.B. Peresh, V.V. Lazarev, O.I. Tzigika, E.A. Korneychuk, Izv. Akad. Nauk SSSR Neorg. Mater 27 (1991) 2079. [9] L.A. Slobodijan, I.E. Barchij, E.Yu. Peresh, M.Yu. Sabov, Visn. Uzhgorod Derzh. Univ. Ser. Khim. 3 (1998) 69. [10] V.B. Ufimtzev, A.A. Lobanov, Heterohenium Equilibria in the Technology of the Semiconductors Materials, Metallurgija, Moscow, 1981, in Russian. [11] I.E. Barchij, Ukr. Khim. Zh., in press.
Table 1 Types, temperatures and coordinates of the invariant processes in the Tl 2 S–Tl 5 Se 2 Br–TlBr ternary system Type
Binary Binary Binary Binary
Process
invariant invariant invariant invariant
eutectic eutectic eutectic peritectic
Ternary invariant eutectic Ternary invariant peritectic
e1 e2 e4 p1
(L⇔Tl 5 Se 2 Br1TlBr) (L⇔Tl 6 SeBr 4 1Tl 2 S) (L⇔Tl 5 Se 2 Br1Tl 2 S) (L1TlBr⇔Tl 6 SeBr 4 )
E 1 (L⇔Tl 5 Se 2 Br1Tl 2 S1Tl 6 SeBr 4 ) P (L1TlBr⇔Tl 6 SeBr 4 1Tl 5 Se 2 Br)
T (K)
Coordinates (mol.%) Tl 2 S
Tl 5 Se 2 Br
TlBr
705 690 658 716
– 63 84 47
15 – 16 –
85 37 – 53
632 656
53 41
17 16
30 43