Effect of added TiO2 on the mechanical properties of sintered Al2O3 insulator

The effect of TiO2 additive concentration and sintering temperatures on the densification of alumina (Al2O3) ceramics were investigated. Densified alumina specimens were prepared by uniaxial pressing at a pressure of 60 MPa followed by isothermal heating at either 1400, 1500, or 1600 degrees C for 2 h. The relative density, microstructure, crystallinity, and hardness were investigated, and the correlation between properties and structure was discussed in relation to TiO2 addition and sintering temperature. The densities of the 0.05wt%-TiO2 specimens sintered at 1500 and 1600 degrees C had higher values than the pure alumina specimens. Adding more than 5.0wt% TiO2 lowered the relative density. The maximum achieved density was 99.7% at 0.05wt% TiO2 addition. Shrinkage and hardness analyses confirmed that the sintering temperature for the Al2O3 insulator could be lowered by adding TiO2. The optimal concentration to obtain a dense alumina with high hardness for insulator use was determined to be in the range of 0.05 to 1.0 wt% of TiO2. These results provide fundamental composition and process optimization data for the development of high-dielectric alumina insulators.