High temperature strength of hot pressed ZrB2–20 vol% SiC ceramics based on ZrB2 starting powders prepared by different carbo/boro-thermal reduction routes

ZrB2–20 vol% SiC (ZS) ceramics based on ZrB2 starting powders obtained by different boro/carbo-thermal reductions involving ZrO2 + B4C, ZrO2 + B4C + C, and ZrO2 + B, were fully densified by hot pressing at 1900–2000 °C. The flexural strength of these ZS ceramics was measured from room temperature up to 1600 °C. At 1600 °C, the flexural strength of the ceramics is 460 ± 31, 471 ± 32 and 345 ± 11 MPa, respectively. The evolution of the strength as function of temperature is explained in terms of the differences in oxygen content, nature of fracture, grain sizes, grain boundary phases and microstructural defects.