Syntheses, structures, physical properties, and theoretical study of LaCu{sub 0.40}Te{sub 2}, NdCu{sub 0.37}Te{sub 2}, SmCu{sub 0.34}Te{sub 2}, GdCu{sub 0.33}Te{sub 2}, and DyCu{sub 0.32}Te{sub 2}
Five rare-earth copper tellurides have been synthesized by the reactions of the elements at 1073 K. The isostructural compounds LaCu{sub 0.40}Te{sub 2} (a = 7.7063(13){angstrom}, b = 8.5882(14){angstrom}, c = 6.3115(10){angstrom}, T = 153 K), NdCu{sub 0.37}Te{sub 2} (a = 7.6349(7){angstrom}, b = 8.3980(8){angstrom}, c = 6.18388(6){angstrom}, T = 153 K), SmCu{sub 0.34}Te{sub 2} (a = 7.6003(10){angstrom}, b = 8.3085(11){angstrom}, c = 6.1412(8){angstrom}, T = 153 K), GdCu{sub 0.33}Te{sub 2}(a = 7.5670(15){angstrom}, b = 8.2110(16){angstrom}, c = 6.0893(12){angstrom}, T = 107 K, and DyCu{sub 0.32}Te{sub 2} (a = 7.5278*13){angstrom}, b = 8.1269(14){angstrom}, c = 6.0546(11){angstrom}, T = 107 K) crystallize with four formula units in space group D{sub 2h}{sup 11}-Pbcm of the orthorhombic system. In each, the rare-earth (Ln) atom is coordinated by a bicapped trigonal prism of Te atoms and the Cu atom is coordinated by a tetrahedron of Te atoms. Infinite linear Te{sup (l+x){minus}} chains run parallel to c, with Te-Te distances decreasing from 3.1558(5){angstrom} in LaCu{sub 0.40}Te{sub 2} to 3.0273(3){angstrom} in DyCu{sub 0.32}Te{sub 2}. Both the thermopower and conductivity data in the c direction show LaCu{sub 0.40}Te{sub 2} to be a semiconductor at all temperatures, and NdCu{sub 0.37}Te{sub 2}, SmCu{sub 0.34}Te{sub 2}, and GdCu{sub 0.33}Te{sub 2} to be semiconductors above 150--200 K. The thermopower data for these three compounds exhibit very high peaks of approximately 900 {mu}V/K in the vicinity of 150 K, followed by a rapid decrease at lower temperatures. This behavior deviates from the trend expected for semiconductors. Huckel calculations predict that the Te{sup (l+x){minus}} chains in LnCu{sub x}Te{sub 2} should show metallic properties. Possible reasons for this discrepancy between theory and experiment involve distortions of the Te chains or disorder of the Cu atoms. GdCu{sub 0.33}Te{sub 2} is paramagnetic with {mu}{sub eff} = 7.74(3) {mu}{sub {Beta}}, typical for Gd{sup 3+}.
- Research Organization:
- Northwestern Univ., Evanston, IL (US)
- OSTI ID:
- 20017341
- Journal Information:
- Journal of the American Chemical Society, Vol. 122, Issue 1; Other Information: PBD: 12 Jan 2000; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
Similar Records
Copper-indium ordering in RECu{sub 6}In{sub 6} (RE=Y, Ce, Pr, Nd, Gd, Tb, Dy)
Local Distortions and Metal–Semiconductor–Metal Transition in Quasi-One-Dimensional Nanowire Compounds AV3Q3Oδ (A = K, Rb, Cs and Q = Se, Te)