SILICON PHOSPHORUS NITRIDE, THE 1ST TERNARY COMPOUND IN THE SILICON PHOSPHORUS-NITROGEN SYSTEM

The novel compound SiPN3 has been prepared by reacting hexachloro-N-silylphosphinimine Cl3Si-N=PCl3 with liquid ammonia at -78-degrees-C followed by subsequent removal of the ammonium chloride byproduct and annealing of the resulting polymeric imide at 800-degrees-C for 12 h. The compound has been characterized by elemental analysis and Si-29 and P-31 MAS-NMR, as well as X-ray powder diffraction methods. The powder data suggest a defect Wurtzite type structure which is closely related to the structures of Si2N2O and Si2N2NH. (Rietveld analysis data: space group Cmc2(1), Z = 4, a = 902.4(4) pm, b = 527.5(2) pm, c = 469.8(2) pm; 44 reflections observed; scan range 10-degrees < 2theta < 81-degrees; germanium monochromator, Cu Kalpha1, R(wp) = 0.047, R(I,h,k,l) = 0.071.) At 920-degrees-C SiPN3 decomposes into Si3N4, P4, and N2. The Si3N4 obtained on pyrolysis of SiPN3 consists of a pure alpha-phase and has an extremely low oxygen content.