Abstract :
Under the influence of heat and in contact with a reactive transition metal, silicon nitride can be transformed from an electrical insulator to the conductive metal nitride (TiN). In particular, the transformation from Si3N4 to TiN is thermodynamically favored, and its otherwise sluggish kinetics can be enhanced by the substitution of titanium alloys with low melting points. To explore this concept, metal and silicon nitride powders were homogenized, pressed into disks and annealed at temperatures ranging from 700ºC to 900ºC before being analyzed with x-ray diffraction (XRD). Compositions, temperature ranges, and phase equilibria were varied systematically to create three unambiguous experiments. The first experiment identified the temperature at which a Ti-Sn alloy with the 6:5 ratio reacts with SiNx, in this case, 750ºC. The second experiment explored if eutectic liquids with even lower melting points could further enhance kinetics. To do so, eutectic Bi-Sn powder was added to a set of titanium-tin mixtures spanning 25% to 75% Ti. Bi did not reduce the onset temperature of N-gettering at any composition. The final experiment explored a companion set of reactions between SiNx and hafnium to determine the extent to which thermodynamic driving (i.e., DGHfN < DGTiN) regulates the practical minimum temperature for reaction. The extreme sensitivity of Hf precludes powder experiments where oxygen contamination cannot be avoided. As such, thin film reactions are being pursued currently and will be presented.
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