Preparation and Growth Mechanism of Hexagonal Boron Nitride in the Presence of Lithium Oxide

Abstract The synthesis of hexagonal boron nitride (h‐BN) by the reaction of boron oxide (B 2 O 3 ) and NH 3 represents an environmentally friendly and economical preparation process. Employing a catalyst to improve the issues including low conversion and reaction rate is important to facilitate the implementation of this method. In this study, we studied the effect of adding lithium oxide (Li 2 O) with a mass fraction of 14%–25% on the reaction process between B 2 O 3 and NH 3 at 1000–1200 °C. During the reaction process, Li 2 O reacts with B 2 O 3 to form a lithium borate melt. The lithium borate melt facilitates the diffusion of NH 3 , and benefits to the dissolution and precipitation of BN, thus promoting the growth of h‐BN. A nearly complete conversion to h‐BN was observed by adding Li 2 O with a mass fraction of 17% when heating at 1200 °C for 240 min. The products exhibit good crystallinity (graphitization index of 3.4) and a sheet structure, with a thickness of 32 nm and a diameter of 400–500 nm. These results provide a reference for optimizing the preparation process of h‐BN.