Solid-state properties of hot-pressed TiB2 ceramics

The powders were hot-pressed in graphite dies with various loads up to 45 MPa and the vertex temperature of 1800 °C was held for 1 h. For the pure, non-activated powders theoretical densities between 97.4% and 99.5% were obtained at a pressure of 45 MPa. Hot-pressed activated powders at this pressure led to densities of up to 99.9%. The addition of 0.5 wt.% of various sintering aids also increased the densities. It is shown that pre-alloying TiB2 with CrB2 is to favour over mixing the powders. If TiB2 and the sintering aid were mixed the best result was obtained with Cr2N. Ceramics with high Young's moduli and hardnesses were obtained. The Poisson's ratios of two samples were 0.08 and 0.09, respectively, which are the lowest known values for a ceramic hard material. The heat conductivity of pure TiB2 is approximately 1/4 of that of copper and the electrical resistivity is only 6 times higher than that of copper.