second, the isotropic thermal parameters of the two in-The structures of the two oxides Bi 3 (MSb 2 )O 11 (M β«Ψβ¬ Al, Ga) dependent Bi sites were unusually large. If the latter obhave been refined by Rietveld-type analysis of combined powder servation is confirmed then it is feasible that unusual neutron and X-ray synchrotron diffraction data. The two oxides surface properties would also be observed in the two are isostructural, space group Pn3 ΰ·
, a β«Ψβ¬ 9.43323( 4) A Λfor M β«Ψβ¬ Bi 3 (MSb 2 )O 11 oxides. Al and a β«Ψβ¬ 9.48980(3) A Λfor M β«Ψβ¬ Ga, in which the M and As part of an ongoing study of the structural properties Sb atoms are statistically distributed in a 12g site. The strucof catalysts, we have determined the structures of the two tures can be described as two interpenetrating networks: a nonmetallic oxides Bi 3 (MSb 2 )O 11 (M Ο Al, Ga) using com-M 2/3 Sb 4/3 O 9 array of edge-sharing octahedra and a Bi 2 O 3 array bined powder neutron and X-ray synchrotron diffraction of corner-sharing Bi 8 O 4 stellae quadrangulae. There are two and examined their surface properties. The results of these independent Bi sites, both having distorted coordination geomestudies are described in this paper.
tries. The surface composition of both oxides is essentially identical to that of the bulk. Comparison with previous studies suggests that there may be some coupling between the mobility EXPERIMENTAL of the Bi ions in these oxides and their electronic Bi 3 (GaSb 2 )O 11 and Bi 3 (AlSb 2 )O 11 were prepared by the properties. Β© 1996 Academic Press solid-state reaction of stoichiometric amounts of Bi 2 O 3 (Aldrich, 99.999%), Al 2 O 3 (BDH, 99.9%), Ga 2 O 3 (Aldrich, 99.99%), and Sb 2 O 3 (Aldrich, 99.999%