Synthesis of β-Si3N4 powders via sol-gel process combined with carbothermal reduction and nitridation

Abstract

Polymeric materials are frequently employed as substrate materials due to their high strength and flexibility. The incorporation of ceramic fillers into polymers can further elevate their thermal conductivity, thereby enhancing their suitability as substrate materials for high-power electronics. Among various ceramics, β-Si₃N₄ powder stands out as an ideal filler due to its superior mechanical properties and high thermal conductivity. However, the high reaction temperatures and low production efficiency of the preparation of β-Si₃N₄ powder hinder its widespread adoption. To achieve low-temperature and efficient synthesis of β-Si₃N₄ powder, this study employed tetraethyl orthosilicate as the silicon source and glucose as the carbon source, utilizing a sol-gel process combined with a carbothermal reduction and nitridation. Under optimized conditions of 1520°C for 3 h, β-Si₃N₄ powder with a β phase content approximating 100 wt% was successfully synthesized, exhibiting an approximately isometric particle morphology with a particle size of about 1 μm. The influence of halogen compound additives and Si₃N₄ seeds on the phase transformation of α-Si₃N₄ was investigated. Notably, the introduction of CaCl₂ as an additive and β-Si₃N₄ as a seed, which obviously accelerated the phase transformation of α-Si₃N₄. This research presents an efficient, low-energy method for the preparation of β-Si₃N₄ powder. The β-Si₃N₄ powder holds promising potential as a thermal conductive filler for polymer composites.