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 5 MPa m1/2 for the TaSi2-doped ceramic.