Study of Mullite-IIIa Oxides Ceramics

Abstract

Effect of IIIa oxide additives on bending strength and micro-structure of mullite ceramics produced using two different kinds of powders were investigated. For the mullite powder produced by the arc-melting method, the maximum bending strength of 250MPa at room temperature was obtained with addition of 5.5mol% Y₂O₃, and no degradation of strength was observed at 1200°C. Y₂SiO₅ was detected at grain boundaries by TEM observation, and this seemed to be the cause for the high strength at high temperatures. For the mullite powder produced by the sol-gel method, on the other hand, no effect of Y₂O₃ addition on the bending strength was observed.