1186
JAFAROV et al.
Table 1. Invariant equilibria in system A
mol %
Point in
Equilibrium
Fig. 3
T, K
2Tl2S
2Tl2Te
TlBiS2
e1
e2
L
α + δ1
α + C
γ + δ2
C
42
88
58
–
–
12
608
713
L
e3
p1
p2
P1
P2
P3
–
–
33
62
3
770
815
715
730
650
610
L
38
–
–
L + γ
L + δ2
L + γ
L + C
L + δ2
97
22
31
56
δ1
C + δ2
α + δ2
δ1 + α
53
64
41
25
5
3
L + δ1 + δ2, respectively. Crystallization reaches com- ate. Away from this binary system, the δ1 + δ2 region
broadens, up to 5–6 mol % (Fig. 2).
pletion through univariant reactions (2ê3, ê2ê3, ê1ê2,
and Â3ê1) in the composition ranges 5–9, 12–26, 52–59,
and 98–99 mol % TlBiS2 and through invariant reac-
tions (ê3, ê2, and ê1) in the ranges 9–12, 26–52, and
59–98 mol % TlBiS2 (Tables 1, 2).
The liquidus diagram (Fig. 3) comprises five primary
crystallization fields, bounded by curves and points repre-
senting uni- and invariant equilibria (Tables 1, 2).
REFERENCES
The Tl2S–[TlBi0.333S0.5Te0.5] join (Fig. 1d) is also
not pseudobinary, with a variety of heterogeneous equi-
libria, which can easily be understood by comparing
Fig. 1d with Figs. 2 and 3.
1. Kanatzidis, M.G., Role of Solid State Chemistry in the
Discovery of New Thermoelectric Materials, Semicond.
Semimet., 2001, vol. 69, pp. 51–98.
2. Ioffe, A.F., Poluprovodnikovye termoelementy (Semi-
conductor Thermoelements), Moscow: Akad. Nauk
SSSR, 1960.
3. Shelimova, L.E., Konstantinov, P.P., Karpinskii, O.G.,
et al., Thermoelectric Properties of PbBi4Te7-Based
Anion-Substituted Layered Solid Solutions, Neorg.
Mater., 2004, vol. 40, no. 11, pp. 1307–1313 [Inorg.
Mater. (Engl. Transl.), vol. 40, no. 11, pp. 1146–1152].
Figure 2 shows the 500-K section of the phase dia-
gram of system A, which clearly illustrates the subsoli-
dus phase relations in this system. The α-phase field
extends along the Tl2S–Tl2Te pseudobinary join and is
ꢀ2 mol % in width and 5 mol % in length. The fields of
the δ1- and δ2-phases (Tl2Te- and Tl9BiTe6-based solid
solutions, respectively) extend up to ꢀ12 mol %.
Tl4Bi2S5 dissolves insignificant amounts of other com-
ponents. The homogeneity range of the γ-phase is
ꢀ2 mol % in width. The system contains six two-phase
regions (α + δ1, δ1 + δ2, α + δ2, C + α, C + δ2, γ + δ2)
and three three-phase regions (α + δ1 + δ2, C + α + δ2,
γ + C + δ2). Note that the Tl2Te–Tl9BiTe6 constituent
4. Jafarov, Ya.I., Mirzoeva, A.M., and Babanly, M.B.,
Reciprocal System 3Tl2S + Bi2Se3
3Tl2Te + Bi2S3,
Zh. Neorg. Khim., 2006, vol. 51, no. 5, pp. 871–875.
5. Jafarov, Ya.I., Mirzoeva, A.M., Shikhiev, Yu.M., and
Babanly, M.B., Reciprocal System 3TlSbS2 + 2Sb2Se3
3TlSbSe2 + 2Sb2S3, Az. Khim. Zh., 2006, no. 2,
pp. 161−165.
6. Ashraf, I.M., Elshaiken, H.A., and Badr, A.M., Charac-
teristics of Photoconductivity in Tl2S Layered Single
Crystals, Phys. Status Solidi B, 2004, vol. 241, no. 4,
pp. 885–894.
binary has a morphotropic phase transition, δ1
δ2,
and the δ1 + δ2 two-phase region is essentially degener-
7. Yamanaka Shinsuke, Kosuga Atsuko, and Kurosaki,
K.J., Thermoelectric Properties of Tl9BiTe6, J. Alloys
Compd., 2003, vol. 352, no. 4. pp. 885–894.
8. Asadov, M.M., Babanly, M.B., and Kuliev, A.A., Phase
Equilibria in the Systems Tl2S–Tl2Se and Tl2S–Tl2Te,
Izv. Akad. Nauk SSSR, Neorg. Mater., 1977, vol. 13,
no. 8, pp. 1520–1521.
9. Babanly, M.B., Kesamanly, M.F., and Kuliev, A.A., Sys-
tem Tl–Tl2S–Bi2S3–Bi, Zh. Neorg. Khim., 1988, vol. 33,
no. 9, pp. 2371–2375.
10. Babanly, M.B., Akhmad’yar, A., and Kuliev, A.A., Sys-
tem Tl2Te–Bi2Te3–Te, Zh. Neorg. Khim., 1985, vol. 30,
no. 9, pp. 2356–2361.
Table 2. Univariant equilibria in system A
Curve
in Fig. 3
Temperature range,
K
Equilibrium
e2 P2
p1 P1
L
α + C
C
713–650
815–730
L + γ
L
e3 P1
p2 P3
770–730
715–610
γ + δ2
δ1
C + δ2
α + δ2
α + δ1
L + δ2
L
P1 P2
P2 P3
730–650
650–610
L
L
P3 e1
610–608
INORGANIC MATERIALS Vol. 44 No. 11 2008