The influence of the growth conditions and process parameters on the formation of blocks during growth of basal-plane-faceted single crystalline sapphire ribbons by the Stepanov/EFG technique was investigated. A number of modifications of the crystallization unit were used to vary systematically the crystal growth conditions. The results gave clearly the growth conditions which are favorable to get blocks-free single crystalline basal-plane-faceted sapphire ribbons. (C) 2012 Elsevier B.V. All rights reserved.