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The TlSe–TlBr–TlI quasi-ternary system
L
Journal of Alloys and Compounds 358 (2003) 93–97
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The TlSe–TlBr–TlI quasi-ternary system I.E. Barchij, E.Yu. Peresh, N.J. Haborets*, V.V. Tzigika Department of Chemistry, Uzhgorod National University, Pidgirna Av. 46, 88000 Uzhgorod, Ukraine Received 5 November 2002; received in revised form 23 January 2003; accepted 23 January 2003
Abstract An investigation of phase equilibria in the TlSe–TlBr–TlI quasi-ternary system was investigated by DTA and X-ray diffraction in combination with mathematical modeling. The projection of liquidus surface, the vertical section and the isothermal section at 473 K, and the perspective representation of the phase diagram were constructed. New complex compounds did not form. The system is of the monovariant eutectic type. The three-dimensional one-, two- and three-phase regions present in the TlSe–TlBr–TlI ternary system are described. 2003 Elsevier B.V. All rights reserved. Keywords: Semiconductors; Phase diagram; Thermal analysis; X-ray diffraction
1. Introduction The TlSe–TlBr–TlI quasi-ternary system is interesting for investigation because of the presence of binary compounds, which reveal optical and semiconductor properties and have practical application. Moreover, the phase equilibria in this system are known. TlSe, TlBr and TlI melt congruently at 611 [1,2], 733 [3] and 713 K [4], respectively. Tl 1 and Tl 13 ions are present in the structure of thallium(II) selenide. According to this fact, the TlSe binary compound is a mixture of thallium(I) and thallium(III) selenides (Tl 2 Se3Tl 2 Se 3 ) [2,5]. It is characterized by a chain structure and a 3D net of tetrahedrons. The tetragonal structure provides two different positions for the thallium atoms. TlBr crystallizes in a cubic structure [7]. TlI is known to exist in two
modifications—orthorhombic low temperature and cubic high temperature (the temperature of polymorphous transformation is 438 K) [8,9]. The crystal structure parameters of these compounds are shown in Table 1.
2. Quasi-binary systems The phase diagram of the TlSe–TlBr system was investigated by Peresh et al. [10]. It is of the eutectic type. The eutectic occurs at 90 mol.% TlSe (594 K). The extent of the TlSe and TlBr homogeneity range is 5 mol.% at the eutectic temperature and decreases substantially with decreasing temperature. A eutectic reaction also characterizes the phase diagram of the TlSe–TlI system. The results were obtained by
Table 1 Crystallographic parameters of the binary compounds of the TlSe–TlBr–TlI quasi-ternary system Compound
Syngony
Space group
a (nm)
b (nm)
c (nm)
Refs.
TlSe TlBr Low-TlI High-TlI
Tetragonal Cubic Orthorhombic Cubic
I4 /mcm Pm3 m Cmcm Pm3 m
0.802 0.384 0.524 0.4198
– – 0.475 –
0.700 – 1.292 –
[5,6] [7] [8] [9]
*Corresponding author. E-mail address: [email protected] (N.J. Haborets). 0925-8388 / 03 / $ – see front matter 2003 Elsevier B.V. All rights reserved. doi:10.1016 / S0925-8388(03)00195-6
94
I.E. Barchij et al. / Journal of Alloys and Compounds 358 (2003) 93–97
Peresh et al. [10]. The lines of primary crystallizations cross at the eutectic point with coordinates 50 mol.% TlSe (538 K). The solid solubility ranges of the initial components of the TlSe–TlI system are 10 mol.% at the eutectic temperature and 5 mol.% at 293 K, respectively. The binary systems, which are based on the thallium halogenides, were investigated by Iljasov [11] and Palkin and Polivanova [12]. The TlBr–TlI system is characterized by unlimited solid solution formation (III type of the phase diagrams by Rozeboom). The minimum in the liquidus and solidus curves is at 42 mol.% TlBr and 693 K.
system. Synthesis of the alloys was carried out with highpurity elements (Tl, 99.997 wt.%; Br, 99.9998 wt.%; I, 99.9998 wt.%) in evacuated quartz containers. The highest synthesis temperature was 783–803 K. After exposure to thermal treatment at the highest temperature for 14–16 h, slow cooling (25–30 K / h) of the samples to 423 K took place. The alloys were annealed for 600 h at this temperature and then quenched in cold water.
4. Results
4.1. TlBr–e2 section 3. Experimental procedure In the course of this study, the classical methods of physicochemical analysis, such as differential thermal (DTA) and X-ray powder diffraction analyses were used in combination with the simplex method of mathematical modeling of phase equilibria in multicomponent systems. The samples were heated and cooled in a furnace using an RIF-101 programmer, which provided a linear temperature variation. The heating rate was 250–320 K / h. The temperature was measured using a Chromel–Alumel thermocouple with an accuracy of 65 K. X-ray powder diffraction was carried out on a DRON-3 diffractometer (Cu Ka radiation, Ni filter). Peak intensities were estimated from the peak area and normalized to the 10-point scale. The simplex method of computer simulation of phase equilibria was described by Barchij [13]. This method provided good results and allows a shortening of the number of alloys in the ternary system. Twenty-five alloys were prepared for the investigation of the TlSe–TlBr–TlI quasi-ternary system. Their compositions and distribution over the concentration triangle are shown in Fig. 1. The composition of the investigated alloys in this section is given in mole percent of one of the components of the section or one of the components of the
Fig. 1. Composition of the investigated alloys in the TlSe–TlBr–TlI quasi-ternary system.
The preliminary experiments carried out by us enabled us to verify the eutectic point coordinates in the TlSe–TlI binary system, which correspond to 590 K and 47 mol.% TlSe (e2, the eutectic point in the TlSe–TlBr–TlI ternary system). The TlBr–e2 system is a vertical section of the TlSe–TlBr–TlI quasi-ternary system (Fig. 2). It intersects the field of primary crystallization of the a-phase (the solid solution of TlBr and the high temperature phase of TlI). The field of the secondary crystallization of the binary eutectic L⇔a1b (b-phase formed on the basis of TlSe) takes place below the liquidus. According to the results of X-ray analyses the solid alloys contain two binary phases a1b, b1g (g-phase formed on the basis of TlBr and the TlI low temperature modification), one a- and a1b1g ternary phases. Thallium bromide concentration increases results in a decrease of the polymorphous transformation of TlI.
4.2. TlSe–TlBr–TlI liquidus surface According to the results of the investigation by the DTA and simplex methods the TlSe–TlBr–TlI liquidus surface projection at the concentration triangle was constructed (Fig. 3). Two fields of primary crystallization characterize this projection: a-phase (bordered by TlBr–e1–e2–TlI– TlBr) and b-phase (bordered by TlSe–e1–e2–TlSe). The
Fig. 2. Phase diagram of the TlBr–e2 vertical section.
I.E. Barchij et al. / Journal of Alloys and Compounds 358 (2003) 93–97
Fig. 3. Projection of the liquidus surface of the TlSe–TlBr–TlI ternary system.
fields of primary crystallization are divided by the e1–e2 monovariant line, which occurs in the temperature range 595–590 K, and two binary nonvariant points. The curve of the monovariant equilibria was described using the polynomial analyses of three vertical sections (10, 20 and
95
Fig. 5. Perspective representation of the TlSe–TlBr–TlI quasi-ternary system.
30 mol.% TlI isoconcentration sections). For example, the results of the polynomial analysis of a–a9 sections (isoconcentration of 10 mol.% TlI) are shown in Fig. 4 and Table 2. The primary crystallization curves of the a- and b-phases are described by the polynomial Y 5 a 0 1 a 1 X 1 a 2 X 2 (Y represents the temperature of crystallization in K, X is the concentration in mol.% and a 0 , a 1 , a 2 are polynomial coefficients). The polynomial curves meet at the point, which is situated on the e1–e2 monovariant line of the TlSe–TlBr–TlI quasi-ternary system. It should be noted, that the calculation results provided a good agreement with the experimental data (correlation parameter is 0.9999; root mean square deviation is 0.0136–0.8542).
4.3. TlSe–TlBr–TlI system
Fig. 4. The polynomial curves of a- and b-phases primary crystallization.
Based on the results obtained, we described the character of physicochemical interaction in the TlSe–TlBr–TlI quasi-ternary system. A perspective view of this ternary system is shown in Fig. 5. The points A9, B9 and C9, which are at the edges of a triangular prism, represent the melting
Table 2 The polynomial calculation results of a–a9 sections (isoconcentration by 10 mol.% TlI) Fields of primary crystallization a (TlBr and HTmod.TlI)
Meeting coordinate 90.75
b (TlSe)
a9 (mol.%)
0
11.1
31.1
51.4
71.4
89.3
93.4
95.9
98.6
100
T (K) a0 a1 a2 r SD
720 708 719.2109 20.8542 5.5952310 23 0.9999 0.8542
687
661
630
598
597 599 437.9682 2.5856 29.4523310 23 0.9999 0.0136
601
602
594.2
96
I.E. Barchij et al. / Journal of Alloys and Compounds 358 (2003) 93–97
temperature of corresponding components (TlBr–735 K, TlSe–605 K, TlI–705 K, respectively). The faces of the ternary prism belong to the two TlSe–TlBr and TlSe–TlI binary eutectic type systems and one belongs to the TlBr– TlI system with unlimited solid solution. Three limited solid solutions are formed in the TlSe–TlBr–TlI system: the a-phase (based on TlBr and the HT-modification of TlI), the b-phase (based on TlSe) and the g-phase (based on TlBr and the LT-modification of TlI). Two fields of primary crystallization characterize the liquidus of the ternary system. These are the fields of the a-phase (bordered by A9–e1–e2–C9–A9) and the b-phase (bordered by B9–e1–e2–B9). The monovariant eutectic line e1–e2 divides the liquidus surface of the system and is characterized by the reaction L⇔a1b, which takes place in the temperature range 595–590 K. The solidus of the ternary system consists of three fields: A9–a1–c1–C9–A9 (end of a-phase crystallization), B9–b1–b2–B9 (end of b-phase crystallization) and a1–b1–b2–c1–a1 (end of crystallization of both phases). The subliquidus and supersolidus part consists of two 3D regions of a and b primary crystallization and one volume of secondary crystallization (L1a1b). All complex alloys in the subsolidus part of the TlSe–TlBr–TlI quasi-ternary system below 590 K are in the solid state. The polymorphous interaction between high and low temperature modification, which takes place in the temperature interval, characterizes this region of the
Fig. 6. Isothermal section of the TlSe–TlBr–TlI quasi-ternary system.
solid state. The 3D one-, two- and three-phase regions of the ternary system are shown in Table 3. The X-ray powder diffraction analysis of TlSe–TlBr– TlI alloys of the isothermal section at 423 K demonstrated that the extent of the homogeneity region of the b-phase is about 7 mol.%, for the a- and g-phases it is about 10 mol.% (Fig. 6). New complex compounds were not observed in the ternary system.
Table 3 One-, two- and three-phase 3D regions of the TlSe–TlBr–TlI quasi-ternary system Region
Volume
Region
Volume
a (TlBr1HTmod.TlI)
A9–a1–a2–A–A9 C9–c1–c2–c3–C0–C9 A9–a1–c1–C9–A9 A9–C9–C0–d1–A–A9 d1–d3–c2–C0–d19
b1g
c3–d4–c4–c3 c3–d4–b6–b3–c2–c3 b3–b6–b5–b3 c3–c4–b5–b3–c2–c3
b (TlSe)
B9–b1–b2–B9 B9–b1–b4–B–B9 B9–b2–b3–b5–B–B9 b1–b2–b3–b5–b6–b4–b1
L1a
A9–e1–e2–C9–A9 (liq) A9–a1c1–C9–A9 A9–e1–a1–A9 C9–e2–c1–C9 a1–e1–e2–c1–a1
g (LTmod.TlI)
C0–c3–c4–C–C0 C0–d2–C–C9 d2–d4–c3–C9–d2 c3–c4–d4–c3
L1b
B9–e1–e2–B9 (liq) B9–b1–b2–B9 B9–e1–b1–B9 B9–e2–b2–B9 b1–e1–e2–b2–b1
a1b
a1–b1–b2–c1–a1 a1–b1–b4–a2–a1 a1–c1–c2–d3–a2–a1 b1–b2–b3–b6–b4–b1 c2–d3–b6–b3–c2
L1a1b
a1–e1–e2–c1–a1 b1–e1–e2–b2–b1 a1–b1–b2–c1–a1
a1g
C0–d1–d3–c2–C0 C0–d2–d4–c3–C0 C0–d2–d1–C0 c2–c3–d4–d3–c2 d1–d2–d4–d3–d1 C0–c2–c3–C0
a1b1g
d3–c2–b3–b6–d3 d3–c2–c3–d4–d3 d4–c3–b3–b6–d4 d3–d4–b6–d3
I.E. Barchij et al. / Journal of Alloys and Compounds 358 (2003) 93–97
References [1] A. Tausend, D. Wobig, Z. Phys. Chem. 96 (1975) 199. [2] E.Yu. Turkina, G.M.A. Popova, T.J. Darvojd, M.A. Gurevich, M. Orlova, Zh. Neorg. Khim. 28 (1989) 1351. [3] P.N. Fedorov, M.V. Mahosoev, F.P. Alekseev, in: Chemistry of Gallium, Indium and Thallium, Nauka, Novosibirsk, 1977, in Russian. [4] R. Ripan, I. Chetjanu, Inorganic Chemistry, Mir, Moscow, 1971, in Russian. [5] G.V. Vinogradova, in: Glass formation and Phase Equilibria in the Halcogenides Systems, Nauka, Moscow, 1984, in Russian.
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[6] J. Ketelaar, W. Hart, M. Moerel, D. Polder, Z. Kristallogr. 101 (1939) 396. [7] K. Genchi, F. Kazuo, M. Takoshi, Chem. Lett. 9 (1972) 831. [8] K. Tebbe, U. Georgy, Acta Crystallogr. 42 (1986) 1675. [9] L.M. Shamovskii, A.D. Shushkanov, DAN USSR 181 (1968) 862. [10] E.Y.u. Peresh, V.B. Lazarev, V.V. Tzigika, O.I. Korneychuk, E.A. Iantzo, Izv. Akad. Nauk SSSR. Neorg. Mater. 27 (1991) 2079. [11] I.I. Iljasov, Ukr. Khim. Zh. 39 (1973) 31. [12] A.P. Palkin, T.A. Polivanova, Zh. Neorg. Khim. 9 (1964) 2446. [13] I.E. Barchij, Ukr. Khim. Zh. 67 (2001) 18.
Journal of Alloys and Compounds 358 (2003) 93–97
www.elsevier.com / locate / jallcom
The TlSe–TlBr–TlI quasi-ternary system I.E. Barchij, E.Yu. Peresh, N.J. Haborets*, V.V. Tzigika Department of Chemistry, Uzhgorod National University, Pidgirna Av. 46, 88000 Uzhgorod, Ukraine Received 5 November 2002; received in revised form 23 January 2003; accepted 23 January 2003
Abstract An investigation of phase equilibria in the TlSe–TlBr–TlI quasi-ternary system was investigated by DTA and X-ray diffraction in combination with mathematical modeling. The projection of liquidus surface, the vertical section and the isothermal section at 473 K, and the perspective representation of the phase diagram were constructed. New complex compounds did not form. The system is of the monovariant eutectic type. The three-dimensional one-, two- and three-phase regions present in the TlSe–TlBr–TlI ternary system are described. 2003 Elsevier B.V. All rights reserved. Keywords: Semiconductors; Phase diagram; Thermal analysis; X-ray diffraction
1. Introduction The TlSe–TlBr–TlI quasi-ternary system is interesting for investigation because of the presence of binary compounds, which reveal optical and semiconductor properties and have practical application. Moreover, the phase equilibria in this system are known. TlSe, TlBr and TlI melt congruently at 611 [1,2], 733 [3] and 713 K [4], respectively. Tl 1 and Tl 13 ions are present in the structure of thallium(II) selenide. According to this fact, the TlSe binary compound is a mixture of thallium(I) and thallium(III) selenides (Tl 2 Se3Tl 2 Se 3 ) [2,5]. It is characterized by a chain structure and a 3D net of tetrahedrons. The tetragonal structure provides two different positions for the thallium atoms. TlBr crystallizes in a cubic structure [7]. TlI is known to exist in two
modifications—orthorhombic low temperature and cubic high temperature (the temperature of polymorphous transformation is 438 K) [8,9]. The crystal structure parameters of these compounds are shown in Table 1.
2. Quasi-binary systems The phase diagram of the TlSe–TlBr system was investigated by Peresh et al. [10]. It is of the eutectic type. The eutectic occurs at 90 mol.% TlSe (594 K). The extent of the TlSe and TlBr homogeneity range is 5 mol.% at the eutectic temperature and decreases substantially with decreasing temperature. A eutectic reaction also characterizes the phase diagram of the TlSe–TlI system. The results were obtained by
Table 1 Crystallographic parameters of the binary compounds of the TlSe–TlBr–TlI quasi-ternary system Compound
Syngony
Space group
a (nm)
b (nm)
c (nm)
Refs.
TlSe TlBr Low-TlI High-TlI
Tetragonal Cubic Orthorhombic Cubic
I4 /mcm Pm3 m Cmcm Pm3 m
0.802 0.384 0.524 0.4198
– – 0.475 –
0.700 – 1.292 –
[5,6] [7] [8] [9]
*Corresponding author. E-mail address: [email protected] (N.J. Haborets). 0925-8388 / 03 / $ – see front matter 2003 Elsevier B.V. All rights reserved. doi:10.1016 / S0925-8388(03)00195-6
94
I.E. Barchij et al. / Journal of Alloys and Compounds 358 (2003) 93–97
Peresh et al. [10]. The lines of primary crystallizations cross at the eutectic point with coordinates 50 mol.% TlSe (538 K). The solid solubility ranges of the initial components of the TlSe–TlI system are 10 mol.% at the eutectic temperature and 5 mol.% at 293 K, respectively. The binary systems, which are based on the thallium halogenides, were investigated by Iljasov [11] and Palkin and Polivanova [12]. The TlBr–TlI system is characterized by unlimited solid solution formation (III type of the phase diagrams by Rozeboom). The minimum in the liquidus and solidus curves is at 42 mol.% TlBr and 693 K.
system. Synthesis of the alloys was carried out with highpurity elements (Tl, 99.997 wt.%; Br, 99.9998 wt.%; I, 99.9998 wt.%) in evacuated quartz containers. The highest synthesis temperature was 783–803 K. After exposure to thermal treatment at the highest temperature for 14–16 h, slow cooling (25–30 K / h) of the samples to 423 K took place. The alloys were annealed for 600 h at this temperature and then quenched in cold water.
4. Results
4.1. TlBr–e2 section 3. Experimental procedure In the course of this study, the classical methods of physicochemical analysis, such as differential thermal (DTA) and X-ray powder diffraction analyses were used in combination with the simplex method of mathematical modeling of phase equilibria in multicomponent systems. The samples were heated and cooled in a furnace using an RIF-101 programmer, which provided a linear temperature variation. The heating rate was 250–320 K / h. The temperature was measured using a Chromel–Alumel thermocouple with an accuracy of 65 K. X-ray powder diffraction was carried out on a DRON-3 diffractometer (Cu Ka radiation, Ni filter). Peak intensities were estimated from the peak area and normalized to the 10-point scale. The simplex method of computer simulation of phase equilibria was described by Barchij [13]. This method provided good results and allows a shortening of the number of alloys in the ternary system. Twenty-five alloys were prepared for the investigation of the TlSe–TlBr–TlI quasi-ternary system. Their compositions and distribution over the concentration triangle are shown in Fig. 1. The composition of the investigated alloys in this section is given in mole percent of one of the components of the section or one of the components of the
Fig. 1. Composition of the investigated alloys in the TlSe–TlBr–TlI quasi-ternary system.
The preliminary experiments carried out by us enabled us to verify the eutectic point coordinates in the TlSe–TlI binary system, which correspond to 590 K and 47 mol.% TlSe (e2, the eutectic point in the TlSe–TlBr–TlI ternary system). The TlBr–e2 system is a vertical section of the TlSe–TlBr–TlI quasi-ternary system (Fig. 2). It intersects the field of primary crystallization of the a-phase (the solid solution of TlBr and the high temperature phase of TlI). The field of the secondary crystallization of the binary eutectic L⇔a1b (b-phase formed on the basis of TlSe) takes place below the liquidus. According to the results of X-ray analyses the solid alloys contain two binary phases a1b, b1g (g-phase formed on the basis of TlBr and the TlI low temperature modification), one a- and a1b1g ternary phases. Thallium bromide concentration increases results in a decrease of the polymorphous transformation of TlI.
4.2. TlSe–TlBr–TlI liquidus surface According to the results of the investigation by the DTA and simplex methods the TlSe–TlBr–TlI liquidus surface projection at the concentration triangle was constructed (Fig. 3). Two fields of primary crystallization characterize this projection: a-phase (bordered by TlBr–e1–e2–TlI– TlBr) and b-phase (bordered by TlSe–e1–e2–TlSe). The
Fig. 2. Phase diagram of the TlBr–e2 vertical section.
I.E. Barchij et al. / Journal of Alloys and Compounds 358 (2003) 93–97
Fig. 3. Projection of the liquidus surface of the TlSe–TlBr–TlI ternary system.
fields of primary crystallization are divided by the e1–e2 monovariant line, which occurs in the temperature range 595–590 K, and two binary nonvariant points. The curve of the monovariant equilibria was described using the polynomial analyses of three vertical sections (10, 20 and
95
Fig. 5. Perspective representation of the TlSe–TlBr–TlI quasi-ternary system.
30 mol.% TlI isoconcentration sections). For example, the results of the polynomial analysis of a–a9 sections (isoconcentration of 10 mol.% TlI) are shown in Fig. 4 and Table 2. The primary crystallization curves of the a- and b-phases are described by the polynomial Y 5 a 0 1 a 1 X 1 a 2 X 2 (Y represents the temperature of crystallization in K, X is the concentration in mol.% and a 0 , a 1 , a 2 are polynomial coefficients). The polynomial curves meet at the point, which is situated on the e1–e2 monovariant line of the TlSe–TlBr–TlI quasi-ternary system. It should be noted, that the calculation results provided a good agreement with the experimental data (correlation parameter is 0.9999; root mean square deviation is 0.0136–0.8542).
4.3. TlSe–TlBr–TlI system
Fig. 4. The polynomial curves of a- and b-phases primary crystallization.
Based on the results obtained, we described the character of physicochemical interaction in the TlSe–TlBr–TlI quasi-ternary system. A perspective view of this ternary system is shown in Fig. 5. The points A9, B9 and C9, which are at the edges of a triangular prism, represent the melting
Table 2 The polynomial calculation results of a–a9 sections (isoconcentration by 10 mol.% TlI) Fields of primary crystallization a (TlBr and HTmod.TlI)
Meeting coordinate 90.75
b (TlSe)
a9 (mol.%)
0
11.1
31.1
51.4
71.4
89.3
93.4
95.9
98.6
100
T (K) a0 a1 a2 r SD
720 708 719.2109 20.8542 5.5952310 23 0.9999 0.8542
687
661
630
598
597 599 437.9682 2.5856 29.4523310 23 0.9999 0.0136
601
602
594.2
96
I.E. Barchij et al. / Journal of Alloys and Compounds 358 (2003) 93–97
temperature of corresponding components (TlBr–735 K, TlSe–605 K, TlI–705 K, respectively). The faces of the ternary prism belong to the two TlSe–TlBr and TlSe–TlI binary eutectic type systems and one belongs to the TlBr– TlI system with unlimited solid solution. Three limited solid solutions are formed in the TlSe–TlBr–TlI system: the a-phase (based on TlBr and the HT-modification of TlI), the b-phase (based on TlSe) and the g-phase (based on TlBr and the LT-modification of TlI). Two fields of primary crystallization characterize the liquidus of the ternary system. These are the fields of the a-phase (bordered by A9–e1–e2–C9–A9) and the b-phase (bordered by B9–e1–e2–B9). The monovariant eutectic line e1–e2 divides the liquidus surface of the system and is characterized by the reaction L⇔a1b, which takes place in the temperature range 595–590 K. The solidus of the ternary system consists of three fields: A9–a1–c1–C9–A9 (end of a-phase crystallization), B9–b1–b2–B9 (end of b-phase crystallization) and a1–b1–b2–c1–a1 (end of crystallization of both phases). The subliquidus and supersolidus part consists of two 3D regions of a and b primary crystallization and one volume of secondary crystallization (L1a1b). All complex alloys in the subsolidus part of the TlSe–TlBr–TlI quasi-ternary system below 590 K are in the solid state. The polymorphous interaction between high and low temperature modification, which takes place in the temperature interval, characterizes this region of the
Fig. 6. Isothermal section of the TlSe–TlBr–TlI quasi-ternary system.
solid state. The 3D one-, two- and three-phase regions of the ternary system are shown in Table 3. The X-ray powder diffraction analysis of TlSe–TlBr– TlI alloys of the isothermal section at 423 K demonstrated that the extent of the homogeneity region of the b-phase is about 7 mol.%, for the a- and g-phases it is about 10 mol.% (Fig. 6). New complex compounds were not observed in the ternary system.
Table 3 One-, two- and three-phase 3D regions of the TlSe–TlBr–TlI quasi-ternary system Region
Volume
Region
Volume
a (TlBr1HTmod.TlI)
A9–a1–a2–A–A9 C9–c1–c2–c3–C0–C9 A9–a1–c1–C9–A9 A9–C9–C0–d1–A–A9 d1–d3–c2–C0–d19
b1g
c3–d4–c4–c3 c3–d4–b6–b3–c2–c3 b3–b6–b5–b3 c3–c4–b5–b3–c2–c3
b (TlSe)
B9–b1–b2–B9 B9–b1–b4–B–B9 B9–b2–b3–b5–B–B9 b1–b2–b3–b5–b6–b4–b1
L1a
A9–e1–e2–C9–A9 (liq) A9–a1c1–C9–A9 A9–e1–a1–A9 C9–e2–c1–C9 a1–e1–e2–c1–a1
g (LTmod.TlI)
C0–c3–c4–C–C0 C0–d2–C–C9 d2–d4–c3–C9–d2 c3–c4–d4–c3
L1b
B9–e1–e2–B9 (liq) B9–b1–b2–B9 B9–e1–b1–B9 B9–e2–b2–B9 b1–e1–e2–b2–b1
a1b
a1–b1–b2–c1–a1 a1–b1–b4–a2–a1 a1–c1–c2–d3–a2–a1 b1–b2–b3–b6–b4–b1 c2–d3–b6–b3–c2
L1a1b
a1–e1–e2–c1–a1 b1–e1–e2–b2–b1 a1–b1–b2–c1–a1
a1g
C0–d1–d3–c2–C0 C0–d2–d4–c3–C0 C0–d2–d1–C0 c2–c3–d4–d3–c2 d1–d2–d4–d3–d1 C0–c2–c3–C0
a1b1g
d3–c2–b3–b6–d3 d3–c2–c3–d4–d3 d4–c3–b3–b6–d4 d3–d4–b6–d3
I.E. Barchij et al. / Journal of Alloys and Compounds 358 (2003) 93–97
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