Synthesis of ZrB2 powders by carbothermal and borothermal reduction

► Three different reductions were completed at low temperature (1250°C). ► Using ZrO2+B2O3+C and ZrO2+B4C+C, there were rod shape growth and impurities. ► Using ZrO2+B4C, there was little rod shape growth. ► Using ZrO2+B4C, there was impurity B2O3 which was easily removed by washing. ► Prepared ZrB2 has D50=1.1μm and a hexagonal shape, and oxygen content (0.725wt.%). Zirconium diboride (ZrB2) powders were synthesized using ZrO2+B2O3+C (carbothermal reduction), ZrO2+B4C (boron carbide reduction), and ZrO2+B4C+C (combined reduction) with various compositions at 1250°C for 1–3h under flowing argon. ZrB2 powders synthesized using ZrO2+B2O3+C displayed rod shape growth. There was much residual impurity carbon in ZrB2 powders synthesized using ZrO2+B4C+C. When synthesized using ZrO2+B4C, there were the residual impurity B2O3 and little rod shape growth. Residual B2O3 impurities were easily removed by washing with methanol. We concluded that the ZrB2 powder synthesis method using boron carbide reduction is the most desirable way to produce ZrB2 powders among the three synthesis routes. ZrB2 powders synthesized using ZrO2+B4C have a particle size of 1.1μm and a hexagonal shape, and low oxygen content (0.725wt.%).