Bending Strength and Microstructure of Al₂O₃-Y₂O₃-MgO and Al₂O₃-Y₂O₃-ZrO₂-MgO Composite Ceramics

Abstract

Alumina ceramics containing Y2O3 and a small amount of MgO were sintered and their physical properties, such as bulk density, bending strength, and shrinkage, and microstructure were investigated comparing with alumina ceramics containing 3Y-ZrO2 and a small amount of MgO. The results are as follows: (1) The bending strength of the Al2O3-Y2O3-MgO sintered composite showed a relatively high value of 330MPa when it contained 10wt% Y2O3. (2) In the Al2O3-Y2O3-MgO sintered composite containing 30 to 60wt% Y2O3, a great number of pores were generated. (3) Identification of the Al2O3-Y2O3-MgO sintered composite by XRD revealed that the composites containing 10 to 30wt% Y2O3 were composed of α-Al2O3 and 3Y2O3⋅5Al2O3. It was also clarified that the composite containing 60wt% Y2O3 consisted of 3Y2O3⋅5Al2O3 and 2Y2O3⋅Al2O3. (4) Comparison of the Al2O3-Y2O3-MgO sintered composites with the Al2O3-Y2O3-ZrO2-MgO ones showed that the latter were more advantageous in high physical properties and fine grained structure than the former.