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

Abstract

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.