Microstructural development of Si₃N₄–SiC–Y₂O₃ ceramics derived from polymeric precursors

[Si–Y–O–C–N] amorphous powders were synthesized by the pyrolysis at 1000 °C in N₂ of chemically modified perhydropolysilazane using n-decyl alcohol and yttrium tri-methoxide. [Si–Y–O–C–N] amorphous powders yielded a unique fibrous microstructure by heat treatment in N₂ at 1800 °C. The fibrous microstructure was composed of β–Si₃N₄ whiskers of submicron in diameter and more than 10 μm in length. Fully dense Si₃N₄ –SiC–Y₂O₃ ceramics were also fabricated by heat treatment at 1800 °C followed by powder-vehicle hot pressing at 1700 °C. After these two-step processings, [Si–Y–O–C–N] amorphous powders yielded a unique fine-grained microstructure composed of submicron grains with high aspect ratio.