Study On Characteristic Of Si₃N₄ Nanopowder Prepared By ICPECVD

This paper mainly study on the technics of preparing nano- Si3N4 and ICPECVD.seeking for the proper parameter and technics, crystallization of nano-Si3N4 powder with Muffle furnace, probe the new effective way of improving the properties of nano- Si3N4 powder The ion density in the reaction chamber was diagnosed by a Langmuir probe. The rules were obtained under different air pressure, different radio frequency power and different position which the ion density changes about from 1010cm-3 to 1010cm -3 decreasing as the pressure increases and increasing as the power decreases .Because of the ion sheath, the area emerged where the ion density is symmetrical.A set of ICPCVD system has been designed and manufactured through the analysis of the probe diagnosed results. When the output power of the RF is within 200W and the reflection power is within 0.6W, a good matching effect can be gained.The SisN4 nanopowder was prepared by means of ICPECVD by decomposing of SiH4 and N2. Analysis by FT-IR, TEM and XRD reveals the characteristic of Si3N4. The results indicated that Si3N4 nanopowder synthesized by ICPECVD is hexagonal cell β -Si3N4 and the particles is spherical with diameter about 20nm, the distribution of those particles is symmetrical when power is 200W and pressure is 53Pa. However, the Si3N4 is non-crystalline when power is 100W or 150W.The agglomeration and the distribution were important parameter of nanopowder , which were analyzed by the laser light scattering particle-size test instrument. But the result appeared great error because of this instrument itself and high requirement to sample.The result of annealing of silicon nitride showed the β crystal nuclear existing in the origin silicon nitride powder led on the grow of hexagonal 3 -Si3N4 and formed the 3 -Si3N4.