Pyrolytic films, in thicknesses up to 30,000Aå, were produced by the reaction at 900°C. These films were characterized by use of transmission electron microscopy, electron microprobe analysis, measurement of dielectric, and optical properties. It was found that the films were orthorhombic with a fine grained structure. The films did not etch appreciably in hydrofluoric acid. Ellipsometric measurements indicated that the films had an index of refraction of 2.20 ± 0.03 at 5461Aå. In addition, certain areas of the films exhibited slight optical absorption. The optical energy gap was found to be 4.20 eV. The dielectric constant and the loss tangent of the pyrolytic films were measured over the temperature range 78°–488°K and the frequency interval 1–100 kHz and exhibited a surprisingly strong temperature dependence. These results and the electron microprobe results indicate the films are not stoichiometric.