Structure et proprietes physiques des phases Cu2TlX2, Cu3 YTl2X4 (AVEC X = Se, Te et Y = Fe, Ga, Al)

Thermoelectric Properties of TlCu3Te2 and TlCu2Te2

“…2, together with the peak positions calculated from the reported crystal structures. [11][12][13] The XRD patterns of our samples are well consistent with the literature data, so it can be said that we were able to obtain pure compounds with no impurities.…”

“…4. The j of TlCu 2 Te 2 is considerably high (about 8 W m À1 K À1 ), [11][12][13] while that of TlCu 3 Te 2 is extremely low (around 0.5 W m À1 K À1 ). It is well known that the total thermal conductivity (j total ) of solids is mainly composed of two components: lattice thermal conductivity (j lat ) and electronic thermal conductivity (j el ).…”

Electrical properties of low-dimensional chalcogenides TlCu2−X2 (X = Se, Te) and (Tl1−Ba )Cu2Se2

“…Folmer and Jellinek found that the formal oxidation state of copper in most of the copper chalcogenides is Cu + , and that the sulfur is in the closed shell oxidation state of S 2− [1]. In this context, it is easily understood that ternary copper chalcogenides such as KCu 3 S 2 [2], KCuS [3], and BaCu 2 S 2 [4,5] have a semiconductive nature because of the filled bands of 3d 10 state of Cu + , and TlCu 2 X 2 (X = S, Se) [6][7][8][9] and TlCu 4 Se 3 [10], in which the total formal charge of positive ions is smaller than that of negative ions, exhibit a metallic nature with hole conduction. We found that copper-deficient ternary copper chalcogenides, such as ACu 7−x S 4 (A = Tl, K, Rb) [11,12], ␣-and ␤-BaCu 4−x S 3 [13,14], TlCu 3−x S 2 [15], and BaCu 2−x S 2 [15], which are semiconductors in a stoichiometric composition, show p-type metallic conduction, where holes are produced by compensation for the lack of positive charge.…”

“…TlCu 2 X 2 (X = S, Se, Te) adopts a ThCr 2 Si 2 -type structure (I/4 mmm; Z = 2) with Cu 2 X 2 layers separated by Tl sheets [7,8]. Each Cu 2 X 2 layer is made of edge-sharing CuX 4 tetrahedra to form an anti-PbO-type structure.…”

Electrochemical Deposition of the Single Phase TlxCu3 – xSe2 Thin Films

“…3,5 To account for this behavior, Brun et al 5 believed the conductivity was caused by the mixed-valence state of Tl + and Tl 3+ in the lattice. However, it was demonstrated by Hall effect that this compound shows hole conductivity.…”