Silicon nitride

Silicon nitride

Names
Preferred IUPAC name Silicon nitride
Other names Nierite
Identifiers
CAS Number	12033-89-5 Y
3D model (Jmol)	Interactive image
ChemSpider	2341213 Y
ECHA InfoCard	100.031.620
EC Number	234-796-8
MeSH	Silicon+nitride
PubChem	3084099
InChI InChI=1S/N4Si3/c1-5-2-6(1)3(5)7(1,2)4(5)6 Y Key: HQVNEWCFYHHQES-UHFFFAOYSA-N Y InChI=1S/N4Si3/c1-5-2-6(1)3(5)7(1,2)4(5)6 Key: HQVNEWCFYHHQES-UHFFFAOYSA-N InChI=1/N4Si3/c1-5-2-6(1)3(5)7(1,2)4(5)6 Key: HQVNEWCFYHHQES-UHFFFAOYAJ
SMILES N13[Si]25N4[Si]16N2[Si]34N56
Properties
Chemical formula	Si3N4
Molar mass	140.28 g·mol−1
Appearance	grey, odorless powder
Density	3.2 g/cm3, solid
Melting point	1,900 °C; 3,452 °F; 2,173 K (decomposes)
Solubility in water	Insoluble
Refractive index (nD)	2.016
Hazards
Main hazards	When heated to decomposition, silicon nitride may emit toxic fumes of ammonia and ozone. Contact with acids may generate flammable hydrogen gas.
EU classification (DSD)	not listed
Related compounds
Other anions	silicon carbide, silicon dioxide
Other cations	boron nitride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Silicon nitride is a chemical compound of the elements silicon and nitrogen, with the formula Si
3N
4. It is a white, high-melting-point solid that is relatively chemically inert, being attacked by dilute HF and hot H
2SO
4. It is very hard (8.5 on the mohs scale). It is the most thermodynamically stable of the silicon nitrides. Hence, Si
3N
4 is the most commercially important of the silicon nitrides and is generally understood as what is being referred to where the term "silicon nitride" is used.

The material is prepared by heating powdered silicon between 1300 °C and 1400 °C in an atmosphere of nitrogen:

The silicon sample weight increases progressively due to the chemical combination of silicon and nitrogen. Without an iron catalyst, the reaction is complete after several hours (~7), when no further weight increase due to nitrogen absorption (per gram of silicon) is detected. In addition to Si
3N
4, several other silicon nitride phases (with chemical formulas corresponding to varying degrees of nitridation/Si oxidation state) have been reported in the literature, for example, the gaseous disilicon mononitride (Si
2N); silicon mononitride (SiN), and silicon sesquinitride (Si
2N
3), each of which are stoichiometric phases. As with other refractories, the products obtained in these high-temperature syntheses depends on the reaction conditions (e.g. time, temperature, and starting materials including the reactants and container materials), as well as the mode of purification. However, the existence of the sesquinitride has since come into question.