Formation mechanisms of α-Si3N4 crystals from amorphous Si3N4 powder synthesized by a low-temperature liquid-phase method

A facile procedure was provided to obtain amorphous Si3N4 powder via a liquid-phase method, followed by a heat treatment process to realize tailorable shapes for α-Si3N4 crystal, while Si3N4 granules were synthesized and whiskers were inhibited. The influence of the temperature on the particle morphology and growth mechanisms were investigated. Characterizations indicated that the crystallization temperature played an important role in controlling the morphology of α-Si3N4 powder, while the relatively lowly temperature (below 1519 °C) was beneficial to forming whiskers. The growth of Si3N4 whiskers, derive from the reaction between SiO(g) and N2, follows the vapor–solid (VS) mechanism, which is inhibited by the increase in temperature. Instead, higher temperatures were conducive to forming granular structures. Highly crystalline α-Si3N4 granules were prepared at 1550 °C due to Si*(g) and N*(g) recombining to Si3N4 nuclei via the vapor–solid-solid (VSS) mechanism providing a theoretical basis for inhibiting the production of the whiskers.