Sintering Mechanisms and Kinetics for Reaction Hot‐Pressed ZrB 2

Sintering mechanisms and kinetics were investigated for ZrB 2 ceramics produced using reaction hot pressing. Specimens were sintered at temperatures ranging from 1800°C to 2100°C for times up to 120 min. ZrB 2 was the primary phase, although trace amounts of ZrO 2 and C were also detected. Below 2000°C, the densification mechanism was grain‐boundary diffusion with an activation energy of 241 ± 41 kJ/mol. At higher temperatures, the densification mechanism was lattice diffusion with an activation energy of 695 ± 62 kJ/mol. Grain growth exponents were determined to be ~4.5, which indicated that a grain pinning mechanism was active in both temperature regimes. The diffusion coefficients for grain growth were 1.5 × 10 −16 cm 4 /s at 1900°C and 2.1 × 10 −15 cm 4 /s at 2100°C. This study revealed that dense ZrB 2 ceramics can be produced by reactive hot pressing in shorter times and at lower temperatures than conventional hot pressing of commercial powders.