Crystal Structure and Physical Properties of the New Chalcogenides Ba₃Cu_17–x(S,Te)₁₁ and Ba₃Cu_17–x(S,Te)_11.5 with Two Different Cu Clusters

Abstract

The sulfide-tellurides Ba(3)Cu(17-x)(S,Te)(11) and Ba(3)Cu(17-x)(S,Te)(11.5) were synthesized from the elements in stoichiometric ratios heated to 1073 K, followed by slow cooling to 873 K over 100 h. Ba(3)Cu(17-x)(S,Te)(11) is isostructural to Ba(3)Cu(17-x)(Se,Te)(11) when [S] > [Te], space group R ̅3m, with lattice dimensions of a = 12.009(1) Å, c = 27.764(2) Å, V = 3467.6(5) Å(3), for Ba(3)Cu(15.7(4))S(7.051(5))Te(3.949) (Z = 6). The structure is composed of Cu atoms forming paired hexagonal antiprisms, capped on the two outer hexagonal faces, where each Cu atom is tetrahedrally coordinated by four Q (= S, Te) atoms. The new variant is formed when [Te] > [S]; then Ba(3)Cu(17-x)(S,Te)(11.5) adopts space group Fm3̅m with a = 17.2095(8) Å, V = 5096.9(4) Å(3), for Ba(3)Cu(15.6(2))S(5.33(4))Te(6.17) (Z = 8). This structure consists of eight Te-centered Cu(16) icosioctahedra per cell interconnected by cubic Cu(8) units centered by Q atoms. Electronic structure calculations and property measurements illustrate that these compounds behave as extrinsic p-type semiconductors-toward metallic behavior for the latter compound. With standard oxidation states Ba(2+), Cu(+), and Q(2-), the electron precise formulas are Ba(3)Cu(16)Q(11) and Ba(3)Cu(17)Q(11.5).

Thermoelectric Properties of the Quaternary Chalcogenides BaCu5.9STe6 and BaCu5.9SeTe6

“…8 We have been investigating new barium−copper chalcogenides for several years, aiming to find materials with localized Cu-ion conductivity, where the sixthperiod Ba ions would impede the Cu paths as well as contribute to low thermal conductivity. This research led to the discovery of several new p-type semiconducting materials, including Ba 3 Cu 14−x Te 12 , 9 Ba 6.76 Cu 2.42 Te 14 , 10 16 respectively. All of these materials exhibit Cu clusters (with Cu−Cu bonds) as well as Cu atom deficiencies (hence, the p-type character).…”

“…This research led to the discovery of several new p-type semiconducting materials, including Ba 3 Cu 14– x Te 12 , Ba 6.76 Cu 2.42 Te 14 , Ba 2 Cu 4– x Te 5 and Ba 2 Cu 4– x Se y Te 5– y , Ba 2 Cu 6– x STe 4 and Ba 2 Cu 6– x Se y Te 5– y , BaCu 6– x STe 6 and BaCu 6– x Se 1– y Te 6+ y , and Ba 3 Cu 17– x Se 11– y Te y . One- and three-dimensional metallic properties were found in Ba 2 Cu 7– x Te 6 and Ba 3 Cu 17– x S 11.5– y Te y , respectively. All of these materials exhibit Cu clusters (with Cu–Cu bonds) as well as Cu atom deficiencies (hence, the p-type character) .…”

Oxygen, sulfur, selenium, tellurium and polonium

“…158 The reagents 4 0 -selenouridine and 4 0 -selenocytidine were prepared and applied in the synthesis of 4 0 -selenoRNA. 159 The macrocycle 1,2,4,5,7,8,10,11octaselenacyclododecane (26) was obtained from the reaction of the P-Se heterocycle Woollins reagent with primary and secondary amines and CH 2 X 2 (X = Cl, Br). 160 In conjunction with PhI(OTf) 2 , diphenyl diselenide catalyses the cyclisation of g,d-unsaturated carboxylic acids to 3,6-dihydro-2H-pyran-2-ones.…”

“…25 The sulfide tellurides Ba 3 Cu 17Àx (S,Te) 11 and Ba 3 Cu 17Àx (S,Te) 11.5 were prepared from the elements, the former is isostructural (R-3m) to Ba 3 Cu 17Àx (Se,Te) 11 when [S]4[Te]. 26 Single crystals of the new a-polymorph of BaTeMo 2 O 9 were grown from a flux of TeO 2 and MoO 3 . 27 Within a series of MCuTe 2 O 7 (M = Sr, Ba, or Pb), all the structures contain [CuTe 2 O 7 ] 2layers separated by M 2+ cations, while the strontium and lead derivatives are centrosymmetric and isostructural, the barium compound is noncentrosymmetric and polar.…”

Thermoelectric properties and stability of Ba3Cu16 − xSe11 − yTey

“…Accordingly, the structures of several quaternary barium copper chalcogenides were uncovered. [13][14][15][16][17][18][19][20] Some of these compounds including isostructural Ba 3 Cu 16 − x S 11 − y Te y 19 and Ba 3 Cu 16 − x Se 11 − y Te y 20 only form when mixed occupied chalcogen sites are present. Recently, we proved the high stability of Ba 3 Cu 16 − x S 11 − y Te y under the measurement conditions applied.…”