Enhanced nitridation of silicon powders using in-situ formed La₂O₃ nanoparticles as catalysts

Abstract

Catalytic effect of in-situ formed La₂O₃ nanoparticles (NPs) on the nitridation of Si powders was studied by X-ray diffraction, field emission-scanning electron microscopy and transmission electron microscope. Thermodynamic analysis and the effects of various processing parameters such as addition of catalyst and firing temperature on the nitridation of Si powders were respectively investigated. The results showed that: 1) The La₂O₃ NPs significantly promoted the nitridation rate of Si powders, and complete nitridation was achieved at 1623 K by using 1 wt % La₂O₃ NPs as catalyst; 2) Numerous Si₃N₄ whiskers of 20–300 nm in diameter and tens of microns in length were fabricated in the final product. The Si₃N₄ whiskers which was believed to be governed by vapor-vapor–solid mechanism were verified to have single-crystal nature, growing along [101] direction.