A polysilazane containing iron (PSZI) was synthesized by the polycondensation of silazane lithium salts with FeCl3, and the structure of PSZI was characterized by IR, NMR, and elemental analyses. PSZI was used as an antioxidation additive for methylsilicone oil and rubber. The gelling time of silicone oil was increased from 3 to 1000 h at 300degreesC in air when 5 wt % of PSZI was added. The elongation at break of heat-vulcanized silicone rubber after ageing at 300degreesC for 312 h remained at 130% when 3 wt % of PSZI was added, whereas for the widely used antioxidative stabilizer Fe2O3, the elongation after ageing for 240 h was only 65%. (C) 2003 Wiley Periodicals, Inc.