Synthesis of Ca<Subscript>x</Subscript>Sr<Subscript>1-x</Subscript>WO<Subscript>4</Subscript> by the polymeric precursor method
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In the recent years, the interest concerning to the synthesis of complex oxides, to be applied as electronic ceramics is continuously increasing. One good example is strontium titanate, displaying a perovskite structure, which favors the occurrence of important electronic properties. In the present study, Sr<Subscript>x</Subscript>Co<Subscript>1-x</Subscript>TiO<Subscript>3</Subscript> powders, in which 0≤;x≤;0.3, were synthesized by the polymeric precursor method, achieving good a stoichiometric control and presented a crystalline structure at temperatures as low as 600°C. These systems were thermally and structurally characterized using thermogravimetric analysis (TG/DTA), X-ray diffraction (XRD) and infrared spectroscopy (IR). The TG results of the powder precursors show that the mass loss process observed for the undoped and Co-doped SrTiO<Subscript>3</Subscript> takes place in four well-defined stages. These stages are related to the evaporation of water and to the combustion of the organic matter present in the powder precursors (pyrolysis process). The addition of cobalt to the SrTiO<Subscript>3</Subscript> promotes a decrease in the mass loss and also decreases the final decomposition temperature of the organic matter. The XRD analysis showed a single phase when 10% of Sr<Superscript>2+</Superscript> was replaced by Co<Superscript>2+</Superscript>. When the extent of cobalt substitution was higher than 10 mol% and the substance was heat treated over 900°C, a CoTiO<Subscript>3</Subscript> secondary phase appeared. By means of IR, it was possible to observe the vibration bands related to the Ti-O bonds and to carbonates.
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