An extended inversion boundary which separated 2 large 180º domains in flux-grown crystals was studied by means of nematic liquid-crystal surface-decoration and X-ray projection and sectional topography. Although a non-polar (100) cleavage plate was chosen for the nematic liquid-crystal decoration, the domains appeared under bright optical contrast. The boundary maintained a mainly irregular zig-zag course, and was clearly visualized using both methods. It appeared in strong contrast in 004 X-ray reflections (normal to the polar axis), and was completely invisible in 040 reflections. A large planar boundary segment which was parallel to the polar axis and was inclined at about 40º to the normal to the specimen surface, exhibited a dynamic fringe contrast of stacking-fault type in 004 reflections. A sectional topograph of this segment yielded an ideal hourglass contrast pattern, this proving the absence of any long-range strain and of any tilt of the reflecting (001) planes across the inversion boundary.

Imaging of Inversion Twin Boundaries in Potassium Titanyl Phosphate by Liquid-Crystal Surface Decoration and X-Ray Diffraction Topography. C.Scherf, T.Hahn, G.Heger, N.R.Ivanov, H.Klapper: Philosophical Transactions of the Royal Society, 1999, 357[1761], 2651-8