A novel alternating current-assisted sintering method for rapid densification of Al2O3 ceramics with ultrahigh flexural strength

A novel alternating current-assisted sintering (ACS) technology was applied to prepare Al2O3 ceramics. The results show that, compared to conventional pressureless sintering (PS), the ACS method has remarkable advantages in reducing the sintering temperature and shortening sintering time. Specifically, submicron dense Al2O3 ceramics could be obtained by ACS with a soaking time of 5 min and a sintering temperature of 1400 degrees C. A higher sintering temperature (1500 'C) and longer soaking time (1 h) were necessary for PS to reach a similar density. The maximum flexural strength and hardness of alternating current-assisted sintered (ACSed) samples were 864 MPa and 19.24 GPa, respectively. For the ACSed and pressureless sintered (PSed) samples whose densities and grain sizes were similar, the flexural strength of the ACSed ones was more than 50% higher than that of the PSed ones. The results suggest that the key to achieving rapid densification is the fast heating rate and mechanical load. In conclusion, the ACS technology, whose cost is lower than spark plasma sintering (SPS), is a viable alternative for preparing high performance Al2O3 ceramics.