Thermoelectric Properties of the Thallium-Tellurium Binary Compounds

Abstract

We are paying attention to extremely low thermal conductivity () materials which have a potential to be next generation thermoelectric materials. Most of the extremely low materials that have been reported so far are ternary thallium tellurides such as Ag-Tl-Te ternary system. However, as for Tl-Te binary system, the thermoelectric properties have been scarcely reported. In the present study, the Tl-Te binary compounds, Tl 2 Te, Tl 5 Te 3 , TlTe, and Tl 2 Te 3 , were prepared and their thermoelectric properties were investigated. The of TlTe was relatively high (approximately 4 Wm À1 K À1 at 300 K), while those of Tl 2 Te and Tl 2 Te 3 were extremely low ($0:5 Wm À1 K À1 at 300 K). These compounds indicated relatively high thermoelectric figure of merit ZT, e.g., Tl 2 Te showed the highest value of 0.2 at 586 K.

Multivalley Band Structure and Phonon-Glass Behavior of TlAgTe

“…Clearly, the crystal structure is key for the lattice dynamics and phonon transport properties. Tl-based materials with ultralow κ l recently have been put forward as promising candidates for room temperature thermoelectric power generation. − For example, TlInTe 2 features κ l = 0.5 W/mK due to rattling of Tl atoms inside Te cages . On the other hand, κ l = 0.3 W/mK of Tl 3 VSe 4 originates from Tl 6s 2 lone pairs, which lead to strong lattice anharmonicity, and loose bonding of the heavy Tl atoms, which reduces the group velocities of the acoustic phonon modes…”

Thermodynamic Description of the Te-Tl Binary System Using the Associate Solution Model

“…Therefore, the associated solution description of the liquid phase is more useful for metallic systems. In previous optimization, 5 the c-Tl 5 Te 3 and Tl 2 Te phases have been described as one phase; however, these two components have different thermoelectric properties, 3 and both are potential candidates for thermoelectric materials and should thus be treated as different phases.…”

“…Ternary thallium-telluride alloys, such as Ag-Te-Tl or Cu-Te-Tl, are materials with extremely low thermal conductivity and have the potential to be the next generation of thermoelectric materials. 3 Furthermore, Te-Tl glass is considered a potential new glass for photonic devices. 4 In this case, knowledge of the phase diagram and possible calculations of higherordered systems are very useful.…”

MODELING THE PHASE DIAGRAM OF THE Tl9TbTe6–Tl4PbTe3–Tl9BiTe6 SYSTEM

“…It is known that telluride Tl 5 Te 3 exhibits thermoelectric properties [16]. Due to the peculiarities of the crystal lattice, it has many ternary analogs of the types Tl 9 AX 6 and Tl 4 BX 3 (A -Sb, Bi, In, Au, rare-earth elements; B -Sn, Pb, Mo, Cu, rare-earth elements; X -Se, Te ) [15,[17][18][19][20][21][22][23], also possessing several functional properties, namely optical [24,25], thermoelectric [26][27][28][29], magnetic [30,31], as well as topological insulators properties [32,33].…”