Mechanical Properties and Microstructure of Al_2O_3 Ceramics Superfast Densified by SPS

Al2O3 ceramics were successfully superfast densified by spark plasma sintering (SPS) underthe conditions of heating rate as high as 600℃/min, no holding time at the sintering temperaturefrom 1350 to 1700 ℃ and then fast cooling to 600℃ within 3 minutes. It showed that Al2O3ceramics could reach to a higher density at a lower sintering temperature by SPS, as comparedwith by normal pressureless sintering. The bending strength of pure Al2O3 ceramics super fastdensified by SPS at the temperature range of 1400~1550 ℃ was as high as about 800 MPa, whichis an excellent datum being of more than a double of the bending strength for normal pure Al2O3ceramics. SEM micrographs showed that the intragranular fracture was a preponderant fracturemode in these Al2O3 ceramics being of very high bending strength.