A novel method to synthesize pure-phase Si2N2O powders in a fluidized bed reactor

Si2N2O ceramic, an emerging functional and structural material, has a wide range of applications. However, the preparation of pure-phase Si2N2O powder remains challenging due to the mass transfer resistance and undesirable side reactions in the conventional methods. Herein, a novel molecular approach combined with the decomposition process has been developed to synthesize pure-phase Si2N2O powders. The hydrated Si(NH)2 precursors were synthesized through the chemical vapor deposition (CVD) of SiCl4, NH3, and humidified N2 in a fluidized bed reactor (FBR) in two steps. Then, the hydrated Si(NH)2 precursors were decomposed into amorphous and subsequently transformed into crystalline powders under different temperatures and time. It was found that the molar ratio of N/O of the hydrolyzed Si(NH)2 can be controlled by N2 ventilation time and played an important role in synthesizing high pure Si2N2O powder. When it varied from 2.5:1 to 2:1, pure-phase Si2N2O powder was obtained after heat treatment at 1300–1500 °C, which features a big tolerance for N/O ratios. This newly developed method offered a chance for the preparation of high-quality Si2N2O powder with high efficiency and low cost.