Crystal growth crucible has thin lining esp of iridium - with surrounding shell of cheaper heat resistant matl

摘要

A crucible for melts, esp. for use in crystal growth around a seed crystal, is of a metal having a high melting point and high resistance to oxidising substances, e.g. iridium. The crucible comprises a thin-walled inset of this metal, removably mounted in a supporting, surrounding shell of heat-resistant or high temp. - resistant material. This shell pref. consists of an annular wall and bottom plate. The annular wall is pref. of a material which is oxidn.-resistant at extremely high temps. and which contains metal reinforcement; more specif. it is of plasma-sprayed oxide ceramic, esp. zirconium oxide or aluminium oxide and contains concentric reinforcing cylinders of iridium foil, or rings or iridium, or helical iridium wires. The outside is pref. faced with a protective coating. The prefd. thickness of this coating and of the iridium insert is 0.3 mm. There may be a liquid lubricating layer between the insert and the shell. There is considerable reduction in the quality of iridium required and the cost of processing it. The weight of material in the insert is only 1/5 - 1/10 of the weight of a conventional iridium crucible.