In a first and completely new approach, a vacuum plasma-spray coating technique was used to deposit selective emitting rare-earth oxide films of ytterbia (Yb(2)O(3)) on porous silicon-infiltrated silicon carbide foams (Si-SiC). The plasma-spray coating technique offers a new and promising way to produce selective emitting coatings on different refractory substrates with complex geometries. The adhesion and thermal shock stability were tested until a film thickness of 130 mu m was achieved; the selective emittance of the oxide coating has been found to be dependent on the film thickness. The material combination Si-SiC and Yb(2)O(3), however needs some major improvement regarding high-temperature stability and high thermal cycling loads. In a different approach, the advantage of low emitting Al(2)O(3) fibers and good thermal matching was combined with Yb(2)O(3) slurry coating of flexible alumina (Al(2)O(3)) fiber bundles, formed into a cylindrical shape. The thin fiber structure tried to imitate the famous incandescent mantle emitters of Auer von Welsbach, but with a more rugged structure. Even though the fibers of the woven emitter were thin, the low thermal conductivity of Al(2)O(3) led to a distinct reduction of the surface temperature and emittance, and a shielding effect of the radiation emanating from the hot inner walls by the cooler outer grid structure was inevitable. Optical filters consisting of a water film and of transparent conducting oxides (TCO) have been developed and tested to protect the photocells against overheating and to reflect nonconvertible off-band radiation back to the emitter The water film led to a significant reduction of the cell temperature and increased cell performance, whereas with the TCO filters only a reduction of the cell temperature was observed.