ZrB ₂ Powders Synthesis by Borothermal Reduction

Abstract

High‐purity zirconium diboride (ZrB 2 ) powders with submicrometer particle size were synthesized by borothermal reduction of nanometric ZrO 2 powders in vacuum. The reaction process was experimentally and thermodynamically assessed. B 2 O 3 was identified as a possible intermediate reaction product. ZrO 2 completely converted to ZrB 2 when thermally treated at 1000°C for 2 h in a vacuum, but the removal of residual boron‐related species required a temperature above 1500°C. ZrB 2 powders obtained at 1000°–1200°C showed a faceted morphology, whereas those prepared above 1500°C had a nearly spherical morphology. The particle size that was calculated from the measured surface area increased with the increasing synthesis temperature from 0.15 μm at 1000°C to 0.66 μm at 1650°C. The oxygen content of the ZrB 2 powders synthesized at 1650°C was as low as 0.43 wt%.