The thermal evolution process of a Ta2O5 thin film from a TaCl5 precursor was followed by thermogravimetry combined with mass spectrometry. The TaCl5 coating was prepared by the deposition of dissolved TaCl5 (in 2-propanol) onto a titanium metal support. After evaporation of the solvent, the gellike film was heated in an atmosphere containing 20% O-2 and 80% Ar to 600 degreesC. Mass spectrometric ion intensity curves show the liberation of chlorinated species in a uniform, slow process between 200 and 500 degreesC and in a fast reaction in the 500-600 degreesC range. Bonded solvent is decomposed in an oxidative cracking process between 120 and 220 degreesC, resulting in the formation of elemental carbon trapped in the film. Combustion of trapped carbon takes place in the 500-600 degreesC range resulting in the formation of CO2 gas inclusions in the quickly solidifying surface layer as evidenced by diffuse reflectance Fourier transform infrared spectrometry.