Elastic Moduli and Hardness of Cubic Silicon Nitride

Abstract

The bulk modulus B 0 ‫؍‬ 290(5) GPa and its first pressure derivative B 0 ‫؍‬ 4.9(6) were obtained for c-Si 3 N 4 from volume versus pressure dependence. Measurements were performed under quasi-hydrostatic conditions in a diamond anvil cell to 53 GPa using synchrotron radiation and energy dispersive X-ray powder diffraction. This combined with nanoindentation measurements determined the shear modulus G 0 of c-Si 3 N 4 to be 148(16) GPa. The Vickers microhardness H V (0.5) for dense, oxygen-free c-Si 3 N 4 was estimated to be between 30 and 43 GPa. Both the elastic moduli and microhardness of c-Si 3 N 4 exceed those of the hexagonal counterparts, ␣-and ␤-phases.

Origin of the low compressibility in hard nitride spinels

“…26͒ is too high. In fact, it is even higher than the B 0 ϭ290 GPa value obtained by Zerr et al 25 in ␥-Si 3 N 4 . If the B -V correlations hold for these materials, a much greater compressibility than in ␥-Si 3 N 4 should be expected given the larger unit cell parameter of ␥-Ge 3 N 4 .…”

Phonon spectrum and thermal properties of cubic Si3N4 from first-principles calculations

“…Second, ␥-Si 3 N 4 is a semiconductor with an energy gap of about 3.5 eV 4 -7 and has potential applications in electronics. 8,9 Furthermore, both first-principles calculations and experiments indicate that ␥-Si 3 N 4 has a hardness comparable to the hardest known oxide ͑Stishovite, a high-pressure phase of SiO 2 ), 1,[10][11][12][13] and significantly greater than the hardness of the two well-known hexagonal polymorphs. 14 The ␥-Si 3 N 4 has also a very high resistance in air to oxidation ͑up to 1600 K͒.…”

Novel binary and ternary phases in the Si-C-N system

“…The X-ray powder diffractogram of the room temperature phase displays very broad peaks, which can be attributed to the small particle size of 10-20 nm. The presence of carbodiimide units at T > 150°C is proven by 13 C MAS-NMR and FT-IR spectroscopy. From X-ray powder diffraction data the high-temperature Si(NCN)2 phase was found to have a cubic structure, space group Pn -3m (No.…”

“…11) This material was found to have high elastic moduli and very high hardness (about 40 GPa) as well as to possess exceptional thermal stability, when compared to traditional α -and β -Si3N4. 12), 13) Surprisingly, no experimental attempts to investigate the formation of intermediate compounds in the Si3N4-C3N4 system at high pressures and high temperatures were reported so far.…”