Silicon oxynitride is a

ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...

material with the chemical formula SiO_xN_y. While in amorphous forms its composition can continuously vary between SiO₂ (

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

) and Si₃N₄ (

silicon nitride Silicon nitride is a chemical compound of the elements silicon and nitrogen. is the most thermodynamically stable and commercially important of the silicon nitrides, and the term "silicon nitride" commonly refers to this specific composition. It ...

), the only known intermediate crystalline phase is Si₂N₂O. It is found in nature as the rare mineral sinoite in some meteorites and can be synthesized in the laboratory.

Properties

The crystalline structure of silicon oxynitride is built by SiN₃O tetrahedra connected through oxygen atoms along the ''c'' axis and through nitrogen atoms perpendicular to it. The strong covalent bonding of this structure results in high

flexural strength Flexural strength, also known as modulus of rupture, or bend strength, or transverse rupture strength is a material property, defined as the stress in a material just before it yields in a flexure test. The transverse bending test is most freque ...

and resistance to heating and oxidation up to temperatures of about 1600 °C.

Synthesis

Polycrystalline silicon oxynitride ceramics are primarily produced by nitridation of a mixture of Si and silicon dioxide at a temperature above melting point of silicon (1414 °C), in the range 1420–1500 °C: :3 Si + SiO₂ + 2 N₂ → 2 Si₂N₂O Silicon oxynitride materials with various stoichiometries may also arise as the products of pyrolysis of preceramic polymers, namely polysilanes and polyethoxysilsesquiazane. SiON materials thus obtained are referred to as

polymer derived ceramics Polymer derived ceramics (PDCs) are ceramic materials formed by the pyrolysis of preceramic polymers, usually under inert atmosphere. The compositions of PDCs most commonly include silicon carbide (SiC), silicon oxycarbide (SiOxCy), silicon nitrid ...

or PDCs. By using

preceramic polymers The term preceramic polymer refers to one of various polymeric compounds, which through pyrolysis under appropriate conditions (generally in the absence of oxygen) are converted to ceramic compounds, having high thermal and chemical stability. Cer ...

, dense or porous Si oxynitride ceramics in complex forms can be obtained using shaping techniques more typically applied for polymers.

Applications

Thin films of silicon oxynitride can be grown on silicon using a variety of plasma deposition techniques and used in microelectronics as a dielectric layer alternative to

silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

and

with the advantages of low leakage currents and high thermal stability. These films have an amorphous structure and therefore their chemical composition can widely deviate from Si₂N₂O. By changing the nitrogen/oxygen ratio in these films, their refractive index can be continuously tuned between the value of ~1.45 for silicon dioxide and ~2.0 for silicon nitride. This property is useful for

gradient-index optics Gradient-index (GRIN) optics is the branch of optics covering optical effects produced by a gradient of the refractive index of a material. Such gradual variation can be used to produce lens (optics), lenses with flat surfaces, or lenses that do n ...

components such as

graded-index fiber A graded-index or gradient-index fiber is an optical fiber whose core has a refractive index that decreases with increasing radial distance from the optical axis of the fiber. Because parts of the core closer to the fiber axis have a higher ref ...

s. Silicon oxynitrides can be doped with metal atoms. The most common example is

sialon SiAlON ceramics are a specialist class of high-temperature refractory materials, with high strength at ambient and high temperatures, good thermal shock resistance and exceptional resistance to wetting or corrosion by molten non-ferrous metals, co ...

, a family of quaternary SiAlON compound. Quaternary silicon oxynitrides containing a

lanthanide The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and yttr ...

element, such as La, Eu or/and Ce are used as

phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or vi ...

References

{{reflist, refs= {{cite book, author=Ralf Riedel, title=Ceramics science and technology: Structures, url=https://books.google.com/books?id=I-WFvgkBiEMC&pg=PA97, access-date=8 October 2011, date=18 April 2008, publisher=Wiley-VCH, isbn=978-3-527-31155-2, pages=97– {{cite book, author1=Albert R. Landgrebe, author2=Electrochemical Society. Dielectric Science and Technology Division, author3=Electrochemical Society. High Temperature Materials Division, title=Silicon nitride and silicon dioxide thin insulating films: proceedings of the sixth international symposium, url=https://books.google.com/books?id=aZ4brOPBhXoC&pg=PA191, access-date=8 October 2011, year=2001, publisher=The Electrochemical Society, isbn=978-1-56677-313-3, pages=191– {{cite book, author=E. S. Machlin, title=Materials Science in Microelectronics: The effects of structure on properties in thin films, url=https://books.google.com/books?id=uZNZEgzJltoC&pg=PA36, access-date=8 October 2011, date=9 December 2005, publisher=Elsevier, isbn=978-0-08-044639-4, pages=36– {{cite journal, url=http://www.minsocam.org/msa/ammin/toc/Articles_Free/1997/Rubin_p1001-1006_97.pdf, journal=American Mineralogist, author=A. E. Rubin, title=Sinoite (Si₂N₂O): Crystallization from EL chondrite impact melts, volume=82, page=1001, year=1997, issue=9–10, doi=10.2138/am-1997-9-1016, bibcode=1997AmMin..82.1001R, s2cid=128629202 Ceramic materials Nitrides Oxides Silicon compounds