Bending strength and microstructure of Al2O3 ceramics densified by spark plasma sintering

Al2O3 ceramics were superfast densified using spark plasma sintering (SPS) by heating to a sintering temperature between 1350 and 1700 degrees C at a heating rate of 600 degrees C/min, without holding time, and then fast cooling to 600 degrees C within 3 min. High-density Al2O3 ceramics could be achieved at lower sintering temperatures by SPS, as compared with that by conventional pressureless sintering (PLS). The bending strength of Al2O3 superfast densified by SPS in the range of sintering temperature between 1400 and 1550 degrees C reached values as high as 800 MPa, almost twice that obtained by the PLS. SEM observations indicated that intragranular fracture was the preponderant fracture mode in these samples, resulting in these excellent bending strength values. (C) 2000 Elsevier Science Ltd. All rights reserved.