Abstract: A crucible comprising Al2O3 and at least one selected from rare earth oxides inclusive of Y2O3 as main components and characterized by firing at 500–1,800° C., the distribution of the rare earth oxide at a higher proportion in a fine particle portion having a particle size of up to 0.5 mm than in a coarse particle portion having a particle size in excess of 0.5 mm, and the substantial absence of the reaction product of the rare earth oxide with Al2O3 is suitable for the melting of a rare earth alloy.

Abstract: A crucible comprising Al2O3 and at least one selected from rare earth oxides inclusive of Y2O3 as main components and characterized by firing at 500-1,800° C., the distribution of the rare earth oxide at a higher proportion in a fine particle portion having a particle size of up to 0.5 mm than in a coarse particle portion having a particle size in excess of 0.5 mm, and the substantial absence of the reaction product of the rare earth oxide with Al2O3 is suitable for the melting of a rare earth alloy.

Abstract: A crucible comprising Al2O3 and at least one selected from rare earth oxides inclusive of Y2O3 as main components and characterized by firing at 500-1,800° C., the distribution of the rare earth oxide at a higher proportion in a fine particle portion having a particle size of-up to 0.5 mm than in a coarse particle portion having a particle size in excess of 0.5 mm, and the substantial absence of the reaction product of the rare earth oxide with Al2O3 is suitable for the melting of a rare earth alloy.

Abstract: A silicon carbide member is manufactured by depositing a silicon carbide coating on a substrate of silicon carbide containing free silicon by chemical vapor deposition. By gradually reducing the content of free silicon of the coating such that the coating is made of silicon carbide containing free silicon at the interface with the substrate, but of silicon carbide containing no free silicon at the outer surface, the coating is firmly bonded to the substrate, undergoes little thermal stress and is resistant against cracking and separation upon thermal cycling. The member is suitable for use in the heat treatment of semiconductor elements.

Abstract: An inner tube for use in a semiconductor diffusion furnace is provided comprising a liner or diffusion tube and an insulating layer formed on the entire outer surface of the tube by spraying, typically plasma spraying. The sprayed insulating layer is resistant to deterioration and peeling, ensuring an extended period of service for the tube.

Abstract: Disclosed is a silicon carbide type diffusion tube comprising a diffusion tube base made of reaction-sintered silicon carbide having an iron concentration of 20 ppm or below and a density of 3.0 g/cm.sup.3 or over, and a silicon carbide layer consisting of a high-purity silicon carbide film having an iron concentration of 5 ppm or below deposited on the inner surface of the tube base and a silicon carbide type diffusion tube comprising a diffusion tube base made of reaction-sintered silicon carbide, and a silicon carbide layer consisting of a Si-depleted layer formed in the inner wall of the reaction-sintered silicon carbide tube base and a high-purity silicon carbide film deposited on the Si-depleted layer, said silicon carbide film having a thickness of more than 0.5 mm.