Silicon nitride solid solutions

Sialon is the generic name for the large family of silicon nitride solid solutions containing the basic elements Si, Al, O and N. Over the last three decades, the matrix sialon phases (a-, P-, and 0-) have been developed and various excellent reviews are available (Cao and Metselaar, 1991 Ekstrom and Nygren, 1992 Izhevskiy et al., 2000). In the sialon family, a- and P-sialons offer most interest as engineering ceramics because of their excellent combination of mechanical and high-temperature properties. 

In some instances, subtle changes in the precursor architecture can change the composition and microstructure of the final pyrolysis product. For example, pyrolysis of —[MeHSiNH] — leads to amorphous, silicon carbide nitride (SiCN) solid solutions at >1000°C (see SiCN section). At ca 1500 °C, these material transform to SisN SiC nanocomposites, of interest because they undergo superplastic deformation20. In contrast, chemically identical but isostructural — [F SiNMe] — transforms to Si3N4/carbon nanocomposites on heating, as discussed in more detail below21. 

Silicon nitride ceramics are mostly produced from oc-rich Si3N4 powders which transform during sintering by a solution reprecipitation process to / solid... 

Fig. 5 Experimental data (dotted lines), and the Derjaguin approximation (solid lines on the left diagrams) and its SEI improved prediction (solid lines on the right diagrams) for the interaction force vs. separation distance between a silicon nitride AEM tip and an HOPG surface in 1 mM NaCl solutions (1/k = 9.6 nm. (Erom Ref f)...

Ion-Selective Field Effect Transistors. Ion-selective field effect transistors (ISFETs) are semiconductor devices related to the solid-state detectors used in spectroscopy (discussed in Chapter 5). In this case, the surface of the transistor is covered with silicon nitride, which adsorbs H ions from the sample solution. The degree of adsorption is a function of the pH of the sample solution and the adsorption of H" " ions results in a change in the conductivity of the ISEET channel. The cell requires an external reference electrode. ISEET pH sensors can be made extremely small (about 2 mm ) and are extremely rugged, unlike the fragile glass bulb pH electrode. They have rapid response times and can operate in corrosive samples, slurries, and even wet solids such as food products. The sensor can be scrubbed clean with a toothbrush, stored in a dry condition, and does not require hydrating... 

SiAlONs are ceramics based on the elements of silicon (Si), aluminum (Al), oxygen (O), and nitrogen (N). They are solid solutions based on silicon nitride (Si3N4), with... 

Silicon nitride has two major polymorphs a and P for engineering application, in addition to the amorphous and the cubic polymorph first reported in 1999. Both silicon nitride (Si3N4) and its form in solid solution (SiAlON) have been reviewed in detail " ". 

Since the 1970s, the search for improved materials has led to a better understanding of the role of additives in the densification and microstructural development of silicon nitride-based ceramics and the consequences for final properties [1, 6]. Improvements in powder manufacture and forming techniques and the development of alternative firing processes has led to a complete family of materials including RBSN, HPSN, sintered silicon nitride (SSN), sintered reaction-bonded silicon nitride (SRBSN), gas-pressure sintered silicon nitride (GPSSN), hot isostatically pressed silicon nitride (HIPSN) and silicon nitride alloys or solid solutions termed SiAlONs, based on their elemental components. 

SiAlONs are solid solutions based on the silicon nitride structure [18]. P- SiAlON (P ) is formed when oxygen replaces nitrogen in the P-Si5Ng structure while, at the same time, silicon is replaced by aluminium to maintain charge neutrality [19]. The phase composition is ... 

Sibeon. A solid solution between P-silicon nitride and beryllia, developed as a crucible material for molten silicon. Side Arch. A brick with the two largest faces symmetrically inclined towards each other, see Fig. 1, p39. 

---