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852
PERESH et al.
Properties of Rb2TeBr6, Cs2TeBr6, and Tl2TeBr6 crystals
Compound
Tm, K
ρ, g/cm3
H, MPa
∆mH, kJ/mol
∆mS, J/(mol K)
∆E0, eV
Rb2TeBr6
Cs2TeBr6
Tl2TeBr6
960
1040
810
4.18
4.49
5.61
32
42
15
15
15.7
13.5
26.2
2.14
2.12
2.06
14
21.2
ture of Tl5Se2I, J. Solid. State Chem., 1984, vol. 52,
no. 1, pp. 53–60.
All of the crystals were found to be stable in air.
They actively react with concentrated HNO3 and
H2SO4 and show little or no reaction with toluene, eth-
anol, acetone, and concentrated HCl. Tl2TeBr6 slowly
hydrolyzes in water.
4. Peresh, E.Yu., Lazarev, V.B., Tsigika, V.V., et al., Syn-
thesis, Stoichiometry Range, and Properties of Tl6SI6,
Tl5Se2Br, and Tl5Se2I Single Crystals, Izv. Akad. Nauk
SSSR, Neorg. Mater., 1991, vol. 27, no. 10, pp. 2079–2083.
5. Peresh, E.Yu., Lazarev, V.B., Korniichuk, O.I., et al.,
Phase Equilibria in the Tl2S(Se,Te)–TlI and TlSe–
TlCl(Br,I) Systems, Neorg. Mater., 1993, vol. 29, no. 3,
pp. 406–409 [Inorg. Mater. (Engl. Transl.), vol. 29,
no. 3, pp. 334–337].
6. Peresh, E.Yu., Lazarev, V.B., Barchii, I.E., et al., Disso-
ciation of Molten Tl6S(Se)I4 and Tl5Se2Br(I) and Phase
Equilibria in the Tl6SI4–Tl6SeI4 and Tl5Se2Br–Tl5Se2I
Systems, Neorg. Mater., 1997, vol. 33, no. 4,
pp. 428−430 [Inorg. Mater. (Engl. Transl.), vol. 33,
no. 4, pp. 359–361].
7. Sabov, M.Yu., Trachuk, L.G., Peresh, E.Yu., et al., Prep-
aration and Properties of Tl6XI4 (X = S, Se) Single Crys-
tals, Nauk. Visn. Uzhgorod. Univ., Ser. Khim., 1998,
no. 3, pp. 15–17.
The physicochemical and optical properties of the
crystals are summarized in the table.
From the position of the fundamental absorption
edge, we determined the band gap ∆E0 of the crystals
(table). The optical transmittance of the crystals was
found to be fairly high (60–75% for 2- to 3-mm-thick
samples). The resistivity of the Tl2TeBr6 crystals was
~106 Ω cm.
According to XRD data, Tl2TeBr6 has a tetragonal
structure with lattice parameters a = 10.63(2) Å and c =
10.72(4) Å. The measured density of Tl2TeBr6 (table) is
close to its x-ray density (5.56 g/cm3).
CONCLUSION
8. Grin’ko, V.A., Safonov, V.V., Ksenzenko, V.I., et al.,
Phase Relations in the TeBr4–ABr (A = Alkali Metal)
Systems, Zh. Neorg. Khim., 1972, vol. 17, no. 6,
pp. 1755–1758.
9. Serebrennikova, G.M., Safonov,V.V.,Allakhverdov, G.R.,
et al., Phase Relations in the Rb2Br6Te–Cs2Br6Te Sys-
tem, Zh. Neorg. Khim., 1973, vol. 18, no. 1, pp. 155–158.
The phase relations in the MBr–TeBr4 (M = Tl, Cs,
Rb) systems were studied in detail in the regions of
Tl2TeBr6, Cs2TeBr6, and Rb2TeBr6. Single crystals of
these compounds were grown, and their properties
were investigated.
10. Safonov, V.V., Kuzina, T.V., Titov, L.G., et al., Reactions
between Molten K2Br6Te, Cs2Br6Te, and Tl2Br6Te, Zh.
Neorg. Khim., 1976, vol. 21, no. 2, pp. 585–586.
11. Karanin, Yu.V. and Angelov, I.I., Chistye khimicheskie
veshchestva (Pure Chemical Substances), Moscow:
Khimiya, 1974.
12. Fedorov, P.I., Mokhosoev, M.V., and Alekseev, F.P.,
Khimiya indiya i talliya (The Chemistry of Indium and
Thallium), Novosibirsk: Nauka, 1977.
13. Handbuch der präparativen anorganischen Chemie in
drei Bänden, von Brauer, G., Ed., Stuttgart: Ferdinand
Enke, 1978. Translated under the title Rukovodstvo po
neorganicheskomu suntezu, Moscow: Mir, 1985, vol. 2.
REFERENCES
1. Blachnik, R. and Dreisbach, H.A., Tl6X4S—ein Neuer
Chalkogenhalogentyp in Thalliumsulfid–Thalliumhalo-
genid Systemen, Z. Naturforsch., 1981, vol. 36, no. 12,
pp. 1500–1503.
2. Blachnik, R., Dreisbach, H.A., and Engelen, B., Das
Zustandsdiagramm Thallium(I)iodid–Thallium(I)selenid
und die Kristallstruktur der Verbindungsklasse Tl6X4I,
Z. Naturforsch., 1983, vol. 38, no. 2, pp. 139–142.
3. Blachnik, R. and Dreisbach, H.A., Phase Relations in the
TlX–Tl2Se System (X = Cl, Br, I) and the Crystal Struc-
INORGANIC MATERIALS Vol. 37 No. 8 2001