Synthesis, crystal and electronic structures of new narrow-band-gap semiconducting antimonide oxides RE(3)SbO(3) and RE(8)Sb(3-delta)O(8), with RE = La, Sm, Gd, and Ho.
In the search for high-temperature thermoelectric materials, two families of novel, narrow-band-gap semiconducting antimonide oxides with the compositions RE(3)SbO(3) and RE(8)Sb(3-delta)O(8) (RE = La, Sm, Gd, Ho) have been discovered. Their synthesis was motivated by attempts to open a band gap in the semimetallic RESb binaries through a chemical fusion of RESb and corresponding insulating RE(2)O(3). Temperatures of 1350 degrees C or higher are required to obtain these phases. Both RE(3)SbO(3) and RE(8)Sb(3-delta)O(8) adopt new monoclinic structures with the C2/m space group and feature similar REO frameworks composed of "RE(4)O" tetrahedral units. In both structures, the Sb atoms occupy the empty channels within the REO sublattice. High-purity bulk Sm and Ho samples were prepared and subjected to electrical resistivity measurements. Both the RE(3)SbO(3) and RE(8)Sb(3-delta)O(8) (RE = Sm, Ho) phases exhibit a semiconductor-type electrical behavior. While a small band gap in RE(3)SbO(3) results from the separation of the valence and conduction bands, a band gap in RE(8)Sb(3-delta)O(8) appears to result from the Anderson localization of electrons. The relationship among the composition, crystal structures, and electrical resistivity is analyzed using electronic structure calculations.
Department of Chemistry, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada.
Peng
P
Wang
Scott
S
Forbes
Taras
T
Kolodiazhnyi
Kosuke
K
Kosuda
Yurij
Y
Mozharivskyj