Amorphous silicon oxynitride powder was synthesized by nitridation of high-purity silica in ammonia at 1120°C. The resulting material was X-ray amorphous, and its chemical characteristics were determined by X-ray photoelectron spectroscopy (XPS) and "Si nuclear magnetic resonance (NMR). The XPS analysis showed a shift to lower binding energies for the Si2p peak with increasing nitrogen content. Upon initial nitridation, the full width at half maximum (FWHM) of the Si2p peak increased, but decreased again at higher nitrogen contents, thus showing the formation of a silicon oxynitride phase with a single or small range of composition. The "Si NMR analysis showed the formation of (amorphous) Si,N, (Si-N,) and possibly two oxynitride phases (Si-N,O, Si-N,O,). It is concluded that while XPS, FT-IR, and nitrogen analysis may show the formation of an homogeneous, amorphous silicon oxynitride (Si,N,O) phase, the formation of phase-pure, amorphous Si,N,O is extremely difficult via this route.

Two high‐purity Si3N4 materials were fabricated by hot isostatic pressing without the presence of sintering additives, using an amorphous laser‐derived Si3N4 powder with different oxygen contents. High‐resolution transmission electron microscopy and electron energy‐loss spectroscopy (EELS) analysis of the Si3N4 materials showed the presence of an amorphous SiO2 grain‐boundary phase in the three‐grain junctions. Spatially resolved EELS analysis indicated the presence of a chemistry similar to silicon oxynitride at the two‐grain junctions, which may be due to partial dissolution of nitrogen in the grain‐boundary film. The chemical composition of the grain‐boundary film was SiNxOy, (x ∼ 0.53 and y ∼ 1.23), and the triple pocket corresponded to the amorphous SiO2 containing ∼2 wt% nitrogen. The equilibrium grain‐boundary‐film thickness was measured and found to be smaller for the material with the lower oxygen content. This difference in thickness has been explained by the presence of the relatively larger calcium concentration in the material with the lower amount of SiO2 grain‐boundary phase, because the concentration of foreign ions has been shown to affect the grain‐boundary thickness.

Solid‐state 29Si NMR techniques were used to characterize laser‐synthesized silicon nitride powder prepared from the reaction of silane with ammonia. When the powder is exposed to water vapor, a hydrated layer rapidly forms at the surface. A comparison of 29Si cross polarization (CP) and Bloch decay (BD)‐MAS‐NMR spectra revealed differences between surface and bulk compositions. CP‐NMR identified Si‐NHx (x = 1, 2) species with a chemical shift of −45 ppm in the as‐synthesized (unexposed) powder. In BD‐NMR spectra, the nitride resonance is observed at −48 ppm. For the hydrated powder, CP‐NMR identified additional =Si‐OH (Q3), =Si‐(OH)2 (Q2), and SiO2 (Q4) species present at the surface. The CP‐NMR spectra were corrected for TlpH relaxation effects and deconvoluted into individual components in order to extract quantitative measurements of the various species present.

The Fused Deposition technique was used to form piezoelectric ceramic-polymer composites with various architectures. The Fused Deposition technique is a solid freeform fabrication (SFF) process where a 3-D object is built from a 1.75 mm diameter filament fed into a heated extruder head capable of moving in the X-Y direction. The head extrudes fine beads (roads) of material onto a furtureless platform capable of moving in the Z-direction. In this work, two different manufacturing routes, fused deposition modeling (FDMTM) and fused deposition of ceramics (FDC), were use to process lead-zirconate-titanate (PZT) ceramidpolymer composites. In the FDMTM method, polymer molds with various connectivities were fabricated. Molds were infdtrated with a PZT slurry and dried. For the FDC method, PZT-binder fdaments with 50-55 volume % solids loading were extruded and then used as a feed material to fabricate green ceramic structures. The structures were subjected to a binder burn out cycle and sintered. The composite fabrication was completed by embedding the sintered structures in an epoxy polymer. Composites were cut, polished, electroded and poled for electromechanical characterization. Composites with features as fine as 50 pm were fabricated using these methods. Several novel composites with structures which can not be formed by standard methods will be shown and the electromechanical properties will be presented.