The structure of a new calcium intergrowth tungsten bronze, CaxWO3, prepare
d at P = 80 kbar and T = 1670 K, has been studied by high-resolution transm
ission electron microscopy and supplementary techniques. The unit-cell dime
nsions, determined from X-ray powder data, are: a = 10.1500(9), b = 7.4232(
7) and c = 3.7915(4) Angstrom. The crystal structure is of (n)-ITB type wit
h n = 2. It is isotypic with those recently reported for the RE WO bronzes
(RE = Pr and Nd) prepared at P = 50 kbar. Combined electron diffraction and
energy-dispersive X-ray spectroscopy (EDX) studies of thin crystallites sh
owed that the hexagonal tunnels were less than half-filled with Ca atoms (x
= 0.07+/-0.01). Electron diffraction patterns revealed ordered superstruct
ures of (2)-ITB as well as an order-disorder transformation under the inten
se electron beam. A calcium bronze (Ca approximate to(0.12)WO(3)) with an h
exagonal tungsten bronze structure (HTB) was also observed in the sample.