[en] We have investigated the impact of morphological changes of the source material during physical vapor transport growth of silicon carbide on the crystal growth process, i.e. global temperature field and vapor transport between source material and crystal, has been studied. Digital X-ray imaging was performed for monitoring of the ongoing processes inside the SiC source material. Numerical modeling was carried out to study the effect on the crystal growth process. Three different SiC sources with varying grain size were investigated. While the SiC source material undergoes fundamental transitions during growth (i.e. evolution from powder to compressed SiC block) it is found that the global growth process is more stable than one would expect. A key role is played by a condensed disk like structure on top of the source material which is present for all SiC sources. (orig.)