The structure and thermal decomposition process of Ba0.8Sr0.2TiO3 (BST) powders and thin films, which were prepared from a precursor of Sr-doped barium titanate alkoxides, were investigated by means of differential thermal/thermogravimetric analyses (DTA/TGA), X-ray diffractometer (XRD), AFM, and Fourier transform infrared spectroscopy (FTIR) measurements. From the FTIR spectra, it has been possible to observe that gel powders pyrolyzed and crystallized by analyzing the bands of organic functional groups and inorganic oxides. For further determination of the temperature of decomposition and crystallization, DTA/TGA technique was used. The thin films of Ba0.8Sr0.2TiO3 were prepared by spin-on sol-gel process on Si (1 0 0) substrates, the films were crystallized above 600 degrees C, and formed complete perovskite structure around 700 degrees C. The morphology was investigated by atomic force microscope.