Abstract
Polyphosphosilazane (POPHPS), a silicon phosphorus oxynitride precursor, was synthesized by the chemical modification of perhydropolysilazane (PHPS) with dimethyl phosphonate [H(O)P(OCH3)2] in p-xylene and pyridine. The IR, NMR and GC indicated that the SiHx groups in PHPS mainly reacted with the PH groups in dimethyl phosphonate with H2 evolution to generate the (MeO)2POSi environment in POPHPS. An assumed mechanism could therefore involve the reaction between the nucleophilic three-coordinated pyridinium salt [OP(OCH3)2]-[C5H5NH]+, which was formed by the isomerization of dimethyl phosphonate in the presence of pyridine, and the SiH3 groups in PHPS. Thermogravimetry analysis up to 900°C under argon atmosphere revealed that POPHPS showed a ceramic yield of 89 mass%. X-ray diffraction analysis showed that an amorphous material was obtained after pyrolysis under nitrogen atmosphere at 1000°C. Solid-state 29Si and 31P MAS NMR revealed that the product pyrolyzed at 1000°C was composed of SiN4-x(O,C)x (x=0-2) and PN4-xOx (x=1, 2) units.
