Single-crystal X-ray diffraction was used to investigate the structure
of the ternary oxide of approximate formula Bi-14(Sr,Ca)(12)O-33. The
crystal examined was found to have a composition Bi2Sr0.68Ca1.07O4.75
or Bi16Sr5.44Ca8.56O38 as a result of refinement. It crystallizes in
the monoclinic space group (C2/m), with fell parameters a = 21.764 (4)
Angstrom, b = 4.3850 (13) Angstrom, c = 12.905 (3) Angstrom, beta = 1
02.72 (2)degrees, and V 1201.2 (5) Angstrom(3), Strontium and calcium
ions were found to substitute for each other, The structure consists o
f a network of alkaline-earth oxide polyhedra with broad channels para
llel to the b axis, in which the bismuth ions reside. Two out of four
crystallographically distinct Bi ions form infinite Bi-O zigzag ribbon
s of edge-linked Bi-O units, while each of the other two form oxygen c
orner-shared Bi-O chains along b. The lone pair electrons of the Bi io
ns point toward each other in the channels.