Improvement in High-Temperature Properties of Al2O3 Ceramics by Microstructure and Grain Boundary Control

• Published in: Key Engineering Materials 2003-01, Vol.247, p.349-354, Article 349
• Main Authors: Iio, Satoshi, Yamamoto, Hiroshi, Mitsuoka, Takeshi
• Format: Article
• Language: English
• ISSN: 1013-9826; 1662-9795; 1662-9795
• DOI: 10.4028/www.scientific.net/KEM.247.349

Microstructure and grain boundary control of alumina ceramics were studied with emphasis on improving the mechanical properties at elevated temperature. Fully densified alumina ceramics with a grain size < 1 micron were fabricated by pre-sintering and hot isostatic pressing. The fine microstructure in the ceramics contributed to the high room temperature strength and hardness, which were 860 MPa and 21.3 GPa respectively. The alumina had superior mechanical properties at room temperature but the properties degraded rapidly above 1000 C. The addition of a small amount of rare earth oxide from 0.02 to 2 mol% and a reduction in the impurities greatly improved the high-temperature properties. The three-point bending strength at 1200 C for ceramics with 0.05 mol% Yb2O3 without impurities was 560 MPa, which was twice that of high-purity alumina and similar to that of silicon nitride ceramics for high-temperature applications.