A high purity SixGe1-x alloy (x(0)=0.89) 48 mm in length with a maximum diameter of 25 mm was grown by the Czochralski method. Development of the cellular structures was evaluated by observing growth striations in the crystal by means of X-ray topography and optical microscopy. Temporary and fatal cellular structures were detected. Two possible factors were distinguished as being responsible for the origin of the cell formations: an enhancement of the effective growth velocity and a gradual reduction of Si composition. Both factors lead to the occurrence of constitutional supercooling beyond the critical relation between growth velocity and alloy composition. (C) 2009 Elsevier B.V. All rights reserved.