Improving high temperature properties of hot pressed ZrB2–20 vol% SiC ceramic using high purity powders

Fully dense ZrB2–20vol% SiC (ZS) ceramics were fabricated by self-made high purity ZrB2 and SiC powders hot-pressing at 1900 °C/30 MPa. Their properties were compared with other ZS ceramics with the same nominal composition, but prepared by pressureless sintering, using low purity commercially available powders. The hot-pressed composites show superior hardness (17.82 GPa), elastic modulus (504 GPa), flexure strength (462 MPa at 25 °C and 463 MPa at 1300 °C in air), electrical conductivity (7.68×10−6 Ω−1 m−1 at 25 °C), thermal conductivity (93.7 W/(m K) at 25 °C, 77.2 W/(m K) at 1200 °C) and a lower average thermal expansion coefficient (6.66×10−6 K−1 from 25 to 2000 °C) compared to the pressureless sintered materials. The improvement in these properties could be primarily explained by the decrease of impurities and second phase levels in hot pressed samples.