X-ray powder diffraction characterization of the large-volume unit cell of the M8 murataite polytype

Abstract

We have used conventional X-ray powder diffraction to study one of the largest volume inorganic mixed oxide unit-supercell structures done so far. This necessitated some small-angle X-ray scattering-like observations at low angles from <2° 2θto concord with electron diffraction, which had indicated an 8 × 8 × 8 huge volume supercell of a fluorite-type basic sub-cell. Emphasis is on the detection of, possibly very weak, fingerprint, low-angle/long lines/peaks which will indicate the (often unsuspected) presence of complex polytypic arrangements of simple very strong basic sub-cells and so facilitate future synthetic studies.