Different clusters within the Ba(4)M(4-x)A(2)Te(9) (M = Cu, Ag, Au; A = Si, Ge) series: Crystal structures and transport properties

作者：Cui Yanjie; Mayasree Oottil; Assoud Abdeljalil; Kleinke Holger^*

来源：Journal of Alloys and Compounds, 2010, 493(1-2): 70-76.

DOI：10.1016/j.jallcom.2009.12.141

• Telluride
• Crystal structure
• Electronic structure
• Semiconductor
• Physical properties

Three new quaternary tellurides Ba(4)M(4-x)A(2)Te(9), namely Ba4Cu3.75Si2Te9, Ba4Au3.69Ge2Te9, and Ba4Ag3.97Si2Te9, were prepared in evacuated silica tubes at 1023 K. Single crystal X-ray diffraction analysis reveals that these tellurides crystallize in two different structure types: space group Pbam, with lattice parameters of a = 8.6389(3)angstrom, b = 13.5883(4)angstrom, c = 10.2252(3)angstrom, V = 1200.32(7)angstrom(3) (Z = 2) for Ba4Ag3.97Si2Te9, and space group Pnma, with lattice parameters of a = 13.4294(4)angstrom, b = 20.0980(7)angstrom, c = 8.5699(3)angstrom, V = 2313.0(1)angstrom(3) (Z = 4) for Ba4Cu3.75Si2Te9, and a = 13.5808(6)angstrom, b = 20.7033(9)angstrom, c = 8.6418(4)angstrom, V = 2429.8(2)angstrom(3) (Z = 4) for Ba4Au3.69Ge2Te9. The Ag-Si telluride is isostructural with Ba4Cu3.71Ge2Te9 and Ba4Ag3.95Ge2Te9, whereas the two latter ones are isostructural members of a new structure type. Both structure types contain M-4 Clusters and dimeric A(2)Te(6) units; however, the M-Te polyhedra are different, resulting in different structure types. The Pnma variants may be viewed as super structures to the Pbam structures, caused by different orientation of the M-4 Clusters and different M-Te coordination spheres. According to electronic structure calculations and transport property measurements, these three compounds are p-type semiconductors with calculated band gaps of 0.35 eV for the Ag compound, 0.89 eV for the Cu compound and 0.19 eV for the Au compound.

• 出版日期2010-3-18