Synthesis and structural and physical properties of new semiconducting quaternary tellurides: Ba4Ag3.95Ge2Te9 and Ba4Cu3.71Ge2Te9.
Two quaternary tellurides, Ba(4)Ag(3.95)Ge(2)Te(9) and Ba(4)Cu(3.71)Ge(2)Te(9), were prepared in evacuated silica tubes at 750 degrees C. Both tellurides crystallize in space group Pbam, with lattice parameters of a = 8.6835(3) A, b = 13.6421(4) A, c = 10.2612(3) A, and V = 1215.55(7) A(3) (Z = 2) for Ba(4)Ag(3.95)Ge(2)Te(9) and a = 8.6464(2) A, b = 13.5305(4) A, c = 10.0810(3) A, and V = 1179.38(6) A(3) (Z = 2) for Ba(4)Cu(3.71)Ge(2)Te(9). These structures are comprised of planar Ag(4)/Cu(4) clusters and dimeric Ge(2)Te(6) units, which are interconnected through Te atoms into a three-dimensional structure. Several split sites in the case of Ba(4)Cu(3.71)Ge(2)Te(9) are reflected in additional, different clusters, including a linear Cu(3) unit. The covalent Ag-Te/Ge-Te network surrounds a one-dimensional linear channel running along the c direction, encompassing the Ba atoms. Electronic structure calculations and transport property measurements show that these two compounds are p-type semiconductors with calculated band gaps of 0.24 eV for the Ag compound and 1.0 eV for the Cu compound.
Cui
Yanjie
Y
Department of Chemistry, University of Waterloo, Waterloo, ON, Canada N2L 3G1.
Assoud
Abdeljalil
A
Kleinke
Holger
H