Process and device for growing crystal

A device for growing single crystals from a melt in a heated iridium crucible using the Czochralski technique which melt is kept at a temperature substantially above the solidification temperature of said melt in a heated crucible, wherein iridium from said crucible contaminates said melt, which comprises means for cooling at least the bottom of said crucible contacting said melt and the lowest part of the melt resting on the bottom to a temperature above the solidification temperature of said melt but low enough to precipitate said iridium, means for providing an annular space between substantially all of the side walls of said crucible and container for coolant flow in said space, flow distribution means positioned and dimensioned beneath the crucible bottom to provide a greater cooling effect on the bottom of said crucible, said greater cooling effect being sufficient to precipitate said iridium, wherein said cooled region beneath the crucible bottom acts as a nucleation center for precipitation of dissolved iridium and wherein the iridium is precipitated from said region and remains there so that said iridium can no longer enter the crystal, and wherein the service life of the crucible is increased.