Abstract: A process for preparing molded bodies of granular material of silicon, germanium or mixed crystals of these elements. The granular material is introduced into a defined three dimensional mold and a chemical transport reaction is started which proceeds with the transport of silicon or germanium. As a result, the particles of the granular material intergrow with each other and eventually form a solid, porous molded body. By varying the starting material, the transport agent, and by adding dopants, the electrical properties of the product can be varied.