Five X-ray methods (Lang topography, one-crystal rocking curves with s
can-step registration, two-crystal diffractometry, Bond measurements,
detection of double reflections caused by Umweganregung) are used for
real structure examination of SiC bulk crystals. The most important re
sult is that Bond measurements show only relatively weak changes of th
e lattice constants between measuring points of a given sample (deviat
ions lower than 10 ppm for the lattice constant c). However, the other
diagnostic techniques show greater lattice distortions. The differenc
es in the lattice constants between different samples of the same poly
type may reach up to 100 ppm.