Si₃N₄–SiC–Y₂O₃ ceramics derived from yttrium-modified block copolymer of perhydropolysilazane and hydroxy-polycarbosilane

A polymeric precursor for the Si₃N₄–SiC–Y₂O₃ ceramic system was synthesized by block copolymerization of perhydropolysilazane (PHPS) with hydroxy-polycarbosilane (PCS-OH), followed by chemical modification with yttrium methoxide. Fully dense Si₃N₄–SiC–Y₂O₃ ceramics were successfully synthesized by pyrolysis of the polymeric precursor at 1000 °C, followed by hot pressing at 1800 °C in N₂. The resulting ceramics revealed that β–SiC particles were dispersed in a size range of about 10–600 nm, and a large amount of β–SiC submicron particles were segregated at the β–Si₃N₄ matrix grain boundaries. It was found that the yttrium-modified block copolymer of PHPS and PCS-OH yielded unique binary ceramics composed of β–SiC–Y₂O₃ and β–SiC nanoparticle-dispersed Si₃N₄–Y₂O₃.