Patent ID: 8449811

Claim:
A method for manufacture of a calcinated or sintered hollow body, comprising: coating an organic spherical carrier with a powder, which forms a shell of the hollow body, and a binding agent, the hollow body having a spherically curved surface; performing one of the following two steps: (A) forming or arranging at least one elevated portion on a surface of the carrier; and (B) embedding at least one placeholder into the shell, a vertical projection of the at least one elevated portion or the at least one placeholder corresponds to at least a thickness of the shell of the fully sintered hollow body while taking account of a degree of shrinkage of the powder during sintering; and heat treating the carrier to remove organic components and sinter, wherein at least one of the at least one elevated portion and the at least one placeholder is removed by at least one of (a) the heat treatment by conversion into a gas phase of the respective material from which they are made and (b) mechanical removal.