Spark plasma sintering of Hfb2 with low additions of silicides of molybdenum and tantalum

HfB2-based composites containing 3 vol% silicides of molybdenum or tantalum as sintering additives are densified by spark plasma sintering at 1900-2000°C. Mechanical properties are measured up to 1500 ◦C in air. 4-pt Flexural strength values at 1500°C are 480 MPa (64% of the RT value) for the MoSi2 -doped composite and 290 MPa (49% of the RT value) for the TaSi2 -doped composite. The fracture toughness is insensitive to the temperature change and reaches 5MPa m1/2 for the TaSi2-doped ceramic.