PROTECTIVE SHEET FOR CRUCIBLE AND CRUCIBLE DEVICE USING THE SAME

摘要

This invention provides a protective sheet for a crucible, which can prevent damage to an inner crucible, can suppress SiC formation on an outer crucible, and can transfer heat uniformly from the outer crucible to the inner crucible. The protective sheet is a protective sheet for a crucible formed of an expanded graphite, which sheet is disposed between an inner crucible (2) and an outer crucible (3) which constitute a crucible. In this protective sheet, the thermal conductivity in the surface direction is not less than 120 W/(m K), and the gas permeability is less than 1.0 x 10^-4 cm²/s. When the protective sheet is pressed and compressed by applying a pressure of 34.3 MPa in the thickness-wise direction, the compressibility is not less than 20%. The high compressibility offers advantages including that the effect of preventing damage to the inner crucible is high when the inner crucible is inserted, the workability can be improved, and the inclination of the inner crucible within the outer crucible can also be prevented. Furthermore, despite the high compressibility, the thermal conductivity can be maintained at a value high enough to heat the inner crucible uniformly. Furthermore, the gas shielding property can also be maintained. Accordingly, unfavorable phenomena such as the occurrence of SiC formation in the outer crucible and thickness reduction can be prevented.