Solid-state properties of hot-pressed TiB2 ceramics

Due to the increasing industrial interest in TiB₂ the present work was accomplished to establish various solid-state properties of TiB₂ and to study the influence of sintering aids and different powder conditioning methods on the densification behaviour of TiB₂.

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.