“…General Electric Inc. and MSNW Inc. showed very good creep behavior for several orientations of single crystal YAG up to 1700 • C. [17][18][19][20][21] Unfortunately, they also showed that single crystal fibers are limited by a low fracture toughness (K c ) and strength degradation at moderate temperatures caused by flaws that undergo slow crack growth. [22][23][24][25][26][27][28][29][30][31][32] In hopes of overcoming the shortcomings of both polycrystalline and single crystal fibers, two-phase single crystals structures (Directionally Solidified Eutectics [DSE]) have been explored because they should provide better strength, creep resistance, and toughness. The hypothesis here is that the tensile strength and toughness of a eutectic fiber may be increased due to the presence of a large number of interphase boundaries across the fiber cross-section (i.e., a fine transverse phase spacing).…”