Phase of block-type structure and formula FeVWO has been synthesized by a solution method using Fe(NO)·9HO, NHVO and (NH)WO·xHO as a metal precursors. Brown solid obtained after evaporation of water at 60 °C has been heated in air at temperatures selected based on results of measurements with the aid of differential thermal analysis and thermogravimetric analysis up to 1000 °C. Products obtained after selected stages of heating have been investigated with the help of X-ray diffraction, infrared spectroscopy and diffusion reflectance spectroscopy in the near-infrared range. Results of investigations have revealed several stages of thermal decomposition of precursor with the FeVO, monoclinic WO and unknown phase as intermediate products. Single-phase sample of FeVWO has been obtained after heating stage at 800 °C. Tungsten precursor (NH)WO·xHO has been subjected to thermoanalytical and spectroscopic study as well. Process of thermal decomposition of tungsten precursor runs with formation of hexagonal WO and ammonium bronze (NH)WO, with monoclinic WO as a final product of decomposition.