EFFECT OF AL2O3 ON HIGH-TEMPERATURE MECHANICAL-PROPERTIES OF SILICON-NITRIDE WITH YB4SI2O7N2

Effect of Al2O3 on high temperature strength of silicon nitride with Y b4Si2O7N2 was investigated. A silicon nitride was fabricated by hot-pr essing powder mixture including 87.4 mass% Si3N4, 12.1 mass% Yb2O3 and 0.5 mass% Al2O3. For reference, silicon nitride without Al2O3 additio n was fabricated from powder mixture including 0.5 mass% SiO2 instead of Al2O3. Sinterability of silicon nitride with Al2O3 was higher than that of silicon nitride without Al2O3. Room temperature strength of th e materials with Al2O3 was higher than that of the materials without A l2O3. Average strength at 1200 and 1350 degrees C of both materials we re almost same. The strength at 1500 degrees C of the material with Al 2O3 was slightly lower than that of the material without Al2O3. Creep resistance of the material with Al2O3 was lower than that of the mater ials without Al2O3.