Phase diagram for the Tl2Te-Bi2Te3 system

Abstract

The phase equilibria in the TI2Te-Bi2Te3 system were studied by means of cooling curve determination, differential thermal analysis and X-ray diffraction methods; the results obtained with the former two methods were compared, The phase diagram established for the system differed considerably from three others published previously.The T12Te-Bi2Te3 system is one of the possible sections of the ternary TI-Bi-Te system, the phase diagram of which is unknown, although different alloys containing thallium, bismuth and tellurium have already been studied many times. The considerable interest in these alloys is caused by the fact that their components form ternary compounds with semiconductive properties. From among them, the compound TIBiTe 2 is of some importance in studies on semiconductivity [1], yet it is still unknown whether the compound melts congru6ntly or incongruently.The following sections of the TI-Bi-Te system have been investigated so far: Bi2Te3-TIzTe3 [2-5], Bi2Te3-TI [6,7], (50% T1 + 50% Bi/Te [8], BiTe-T1Te [9], BizTe3-T19BiTe6 [10], T12Te-Bi2Te 3 [11,12] and TI2Te-Bi2Te3-Te [13]. The phase equilibria in systems of the type TlzXW-BVX w have been discussed in [14]; it has been found that with increase in atomic weight of an element in Group V or VI of the periodic table, the number of compounds decreases in the succeeding system. For example, if four compounds are formed in the TI2S As2S 3 system, then only one congruently melting compound, of formula T1BiTe2, should be expected in the TI2Te-BizTe 3 system.The investigation results published to date on the TI2Te-Bi2T % system [10-12] differ considerably from one another (the Bi2Te3-TigBiTe 6 system [10] constitutes 90% of the TlzTe-Bi2Te 3 system). In two of these papers [11,12], it has been reported that the alloys rich in Bi2Te 3 form a limited solid solution. According to [10]

Phase diagram for the Tl2Te-SnTe system

“…Results obtained by the method are unreliable especially when the phase transformations occur in succession at temperatures not too distant from one another [2]. In the preliminary examination of the T12Te-SnTe system by differential thermal analysis, we observed within the range 0-55 mole % SnTe a considerable scatter of experimental points, that permitted their at-T/mnua Anat, 3e~ ]ooo rangement to be interpreted in different ways.…”

“…Up to now, systems have been investigated, the second component of which were the tellurides of following metals (M): Ag [1], Bi [2] and Sb [3].…”

Thermoelectric Properties of Tl2Te-Sb2Te3 Pseudo-Binary System

“…On the other hand, some researchers have reported the phase equilibria for the Tl 2 Te-Sb 2 Te 3 pseudo binary system [9]. In this study, we examine the thermoelectric properties of Tl 2 Te-Sb 2 Te 3 pseudo binary system, in which Sb 2 Te 3 content is up to 10 mol.…”