Effects of Y2O3 Additive on Mechanical and Thermal Properties of Cordierite-Mullite Ceramics

Abstract

Cordierite is an alumina-magnesia-silica compound widely used as a thermal shock resistant material due to its high thermal shock resistance, low coefficient of thermal expansion (CTE), low dielectric constant, and good electrical insulation. However, its narrow sintering temperature range and low mechanical strength hinder its application in ceramic heaters. Although mullite shows excellent thermal and chemical stability, heat resistance, and mechanical strength, it has the disadvantages of high sintering temperatures (1600-1700 degrees C) and poor thermal shock resistance. In this study, a composite phase was prepared by mixing cordierite and mullite to expand the narrow sintering temperature range of cordierite and adjust its CTE to be similar to that of Si. Furthermore, Y2O3 was added to reduce the sintering temperature and to increase the mechanical strength. Therefore, the composite showed the highest density of 2.5 g/cm(3) at 1380 degrees C when the ratio of mullite to cordierite was 20 wt%. When 11 wt% Y2O3 was added to this composition, the highest density was 2.8 g/cm3 for a sintering temperature of 1320 degrees C, and the mechanical strength was relatively good as 180 MPa of 3-points bending strength was comparatively good. The CTE was 2x6x10(-6) center dot K (-1), which was similar to that of Si.