Precise Thermodynamics‐Guided Boro/Carbothermal Synthesis of ZrB ₂ Powders

ABSTRACT A quantitative thermodynamic model based on the extreme assumption method and multicomponent multiphase equilibrium thermodynamics were established to control boron excess and carbon deficiency during vacuum boro/carbothermal reduction synthesis of ZrB 2 powders, addressing volatilization of gaseous phases mainly includes BO (g), (BO) 2 (g), and B 2 O 3 (g). Using three systems (ZrO 2 ‐B 4 C, ZrO 2 ‐B, and ZrO 2 ‐B 4 C‐C) at 1600°C as exemplars, all calculated proportions yielded single‐phase ZrB 2 powders with oxygen and carbon contents below 1 wt%. The ZrO 2 ‐B 4 C system gave the lowest oxygen and some rod‐like particles; ZrO 2 ‐B route produced powders with very low carbon but higher oxygen content and coarser particles; ZrO 2 ‐B 4 C‐C system achieved the finest particle size ( D 50 = 0.85 µm) with narrow distribution but slightly higher residual carbon. As‐synthesized powders outperformed most commercial counterparts in oxygen content and particle size. Their impurities mainly originated from raw materials and varied with boron source, which were also briefly discussed.