Microstructure and mechanical properties of rare-earth doped Si3N4 and Si3N4/SiC ceramics

0353412 - ÚFM 2011 RIV CH eng J - Journal Article
Tatarko, P. - Lojanová, Š. - Chlup, Zdeněk - Dusza, J. - Šajgalík, P.
Microstructure and mechanical properties of rare-earth doped Si3N4 and Si3N4/SiC ceramics.
Advances in Science and Technology. Roč. 65, - (2010), s. 78-85. ISSN 1662-0356
Institutional research plan: CEZ:AV0Z20410507
Keywords : silicon nitride * composite * rare-earth element * microstructure * mechanical properties
Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

Microstructure and mechanical properties of Si3N4 and Si3N4 + SiC nanocomposites sintered with rare-earth oxide additives (La2O3, Y2O3, Yb2O3 and Lu2O3) have been investigated. The composites exhibited smaller grain diameter compared to that of monolithic materials. The aspect ratio of β-Si3N4 grains increased with a decreasing ionic radius of rare-earth elements in the Si3N4 monoliths as well as in the Si3N4-SiC nanocomposites. The hardness of both systems increased with a decreasing ionic radius of rare-earth element. The fracture toughness of the materials with coarser microstructure and higher aspect ratio was higher due to the more frequent toughening mechanisms. No significant difference between strength values of monoliths and composites was observed and the strength in the composites was determined mainly by the present processing flaws. Significantly improved creep resistance was observed in the case of composites and for materials with smaller ionic radius of RE3+ .
Permanent Link: http://hdl.handle.net/11104/0192667