Sialon Compounds

Silicon nitride, oxynitride and silicon aluminium oxynitride (SiAlON) compounds are of considerable technical interest as advanced ceramics because of their stability and chemical inertness at elevated temperatures, and their excellent mechanical properties. Si MAS NMR has proved to be useful in studying various aspects of these compounds, including their formation and structure, the processes by which they are... 

Silicon-containing ceramics include the oxide materials, silica and the silicates the binary compounds of silicon with non-metals, principally silicon carbide and silicon nitride silicon oxynitride and the sialons main group and transition metal silicides, and, finally, elemental silicon itself. There is a vigorous research activity throughout the world on the preparation of all of these classes of solid silicon compounds by the newer preparative techniques. In this report, we will focus on silicon carbide and silicon nitride. 

Five aspects of the preparation of solids can be distinguished (i) preparation of a series of compounds in order to investigate a specific property, as exemplified by a series of perovskite oxides to examine their electrical properties or by a series of spinel ferrites to screen their magnetic properties (ii) preparation of unknown members of a structurally related class of solids to extend (or extrapolate) structure-property relations, as exemplified by the synthesis of layered chalcogenides and their intercalates or derivatives of TTF-TCNQ to study their superconductivity (iii) synthesis of a new class of compounds (e.g. sialons, (Si, Al)3(0, N)4, or doped polyacetylenes), with novel structural properties (iv) preparation of known solids of prescribed specifications (crystallinity, shape, purity, etc.) as in the case of crystals of Si, III-V compounds and... 

The sialons are a group of ceramic compounds of increasing technological importance for their thermal, chemical and mechanical properties. These are similar to Si3N4 but can be more readily tailored to specific requirements because of the wide range of possible sialon compositions. 

Of the various known structures for the extensive series of compounds of Si, Al, O and N (the sialons), those most closely related to AIN are the polytypoid sialons (Si,Al)m(0,N)m+i. The non-metal atoms in excess of the 1 1 ratio required by the... 

A new compound formed during a novel silicothermal synthesis of O-sialon from clay, silica and elemental Si was found to have similar Al and Si NMR spectra to O-sialon. This NMR observation led to its subsequent identification as a low-temperature form which was previously unknown because other synthesis methods require higher temperatures, at which the low-temperature form is unstable, and conversion to the more usual high-temperature form has occurred (Barris et al. 1997). 

An Y NMR study has also been made of the effect of Y2O3 on the sintering of the silicon aluminium oxynitride 3-sialon, a compound structurally related to (3-Si3N4 but... 

Figure 8.14. MAS NMR spectra of nitride-based ceramic bodies sintered with 10 wt % MgO and related magnesium silicon nitride compounds. A. Si3N4, from MacKenzie and Meinhold (1994), B. (J-sialon, from MacKenzie and Meinhold (1996), C. X-sialon, from MacKenzie et al. (2000), D. Crystalline MgSiNi (upper) and MgAlSiNj (lower), from MacKenzie and Meinhold (1994). All spectra used by permission of the copyright owner.

Corrosion by Metals Reactions of Si3N4 with metals and alloys are a complex issue, because the atmosphere both for oxygen and nitrogen partial pressures plays a role and silicides, nitrides, or ternary compounds can form. A good compilation of the partly conflicting observations has been provided [116], For the interaction of the related SiAlONs and Fe-based alloys see published work [124]. 

Investigation of structure formation mechanism of SiAlONs (solid solutions of Si3N4-AlN-Al203) under the SHS mode with cooling of the reactive mass (quenching of intermediate products) shows that not only individual compounds... 

In the present book, the material s spectrum concentrates on new or advanced synthesis methods for metallic nitrides and nitrogen compounds - TiN, VN, NbN, TaN, and CrN, as well as on the nonmetallic species - AIN, BN, and SiAlONs. 

Both, Hirosaki et al. [292, 295] and Zhou et al. [296] reported a green oxynitride phosphor based on Eu -doped P-sialon. Other suitable host lattices for phosphors include MSi202N2 compounds (M = Ca, Sr, and Ba) for example, SrSi202N2 Eu " emits a green color, BaSi202N2 Eu + yields blue-green emission, while CaSi202N2 ... 

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