A process for producing silica shell structures is disclosed in U.S. Pat.  No.  5,024,826, which issued on Jun. 18, 1991, the disclosure of which is hereby incorporated by reference. 
A process for coating silica shell structures with a layer of antimony-containing tin oxide, which can be employed for producing electroconductive powders, is described in European Patent Application Publication No.  0359569, which published on Mar. 21, 1990; the disclosure of which also is hereby incorporated by reference.  Such electroconductive powders are useful in electrically conducting coatings but normally not as primary conductors of electricity.