Grain Growth During Gas‐Pressure Sintering of β‐Silicon Nitride

Abstract

The microstructures of gas-pressure-sintered materials from &Si3N4 powder were characterized in terms of the diameter and aspect ratio of the grains. The size distributions of diameters in materials fabricated by heating for 1 h at 1850" to 2000°C were nearly constant when they were normalized by average diameters because of normal grain growth. The ratedetermining step in the densification and grain growth was expected to be the diffusion of materials through the liquid phase. The activation energy for grain growth was 372 kJ/mol. The average aspect ratio of the grains was 3 to 4, whereas that of large grains was smaller because of shape accommodation. The fracture toughness was about the same as that of material from mSi3N4 powder despite the smaller aspect ratio of the grains. [

Processing, Characterization and Mechanical Properties of SiAlONs Produced from Low Cost <i>β</i>-Si₃N₄ Powder

“…Otherwise, coarse grains, even around 1 µm, do not have enough driving force for grain growth. Similar observations were made on -Si 3 N 4 ceramics [25][26][27][28] . After 21 hrs milling, particle size was down to 0.5 µm and B0.5 specimen after sintering have fine elongated microstructure with grain size was around 0.2 µm and aspect ratio was about 7.…”

Comparison of fracture resistance as measured by the indentation fracture method and fracture toughness determined by the single-edge-precracked beam technique using silicon nitrides with different microstructures

“…Aspect ratios of the grains in the 5 and 10k magnification images were estimated from the mean value of the 10% highest observed aspect ratios. 15 Aspect ratios of the coarse grains selected from the micrographs at a magnification of 1k were calculated by the same procedure as mentioned above.…”

Microstructure Control in Silicon Nitride Ceramics-A Review

“…3. 8 The size distribution is nearly the same for all sintering temperatures. It suggests that b grains covered by liquid phase are fairly stable even in fine grains and have a very low growth rate.…”