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 degrees C. The flexural strength of these ZS ceramics was measured from room temperature up to 1600 degrees C. At 1600 degrees 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. (C) 2013 Elsevier Ltd. All rights reserved.