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Perovskite-type barium strontium titanate (BST) thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol-gel route at room temperature. The prepared sol had a narrow particle size distribution of about 20 nm. X-ray diffraction (XRD) revealed that phase composition and preferable orientation growth of BST depended upon the annealing temperature.Transmission electron microscope (TEM) images showed that the crystallite size of the powders decreased with increasing annealing temperature from 8 nm at 25 ℃ down to 5 nm at 800 ℃. Field emission scanning electron microscope (FE-SEM) analysis and atomic force microscope (AFM) images revealed that BST thin films had mesoporous and nanocrystalline structure with average grain size of 30 nm at 600 ℃. Based on Brunauer-Emmett-Teller (BET) analysis, the synthesized BST showed mesoporous structure containing pores with needle and plate shapes and BET surface area in the range of 49-32 m2/g at 500-800 ℃.