The availability of continuous ceramic fibers has had a major impact on the development of new high performance materials. Ceramic fibers can be used in metal matrix as well as in ceramic matrix composites, as high temperature insulation materials or as components in microstructural applications. Although many research activities have recently been focused on non-oxide fibers of the Si-C-N-O type([1-4]) or the Si-Ti-C-O type([2-5]) and on single-crystal oxide fibers([3]) for temperatures above 1400 degrees C, the potential of polycrystalline oxide fibers has not yet been sufficiently examined. There is a demand for different types of fibers in order to check their properties for the applications mentioned above. Currently there are only a few continuous polycrystalline oxide fibers on the market, and these are all based on Al2O3.([2-4])