Controlling the conditions for synthesis of strontium titanate nanopowders from celestite ore

Abstract

Strontium titanate SrTiO₃ nanopowders have been successfully prepared through oxalate precursor route using Egyptian celestite ore. Celestite ore was reduced with the carbon at the annealed temperature of 1100°C for 3 h to obtain water soluble strontium sulphide that treated with a dilute hydrochloric acid to produce strontium chloride. The formed strontium chloride and titanium dioxide were mixed with a certain amount of oxalic acid to form strontium titanium oxalate complexing precursors. The effect of oxalic acid molar ratio, annealing temperature, time and hydrogen peroxide additive on the crystal structure, crystallite size and microstructure was systematically studied. The results revealed that a well crystallite single phase of SrTiO₃ nanopowders was achieved in the presence of hydrogen peroxide using 1·5 molar ratio of oxalic acid at the annealing temperature of 1000°C for 1 h. The crystallite size of the formed powders increased with increasing annealing temperature and time. The crystallite size was in the range between 50 and 80 nm. The SEM images of the formed SrTiO₃ particles appeared as cube-like structure. The band gap energy and the direct current resistivity of the produced powders were ∼3·6 eV and 4·403×10⁴ Ω m respectively for the sample in the presence of 10% hydrogen peroxide annealed at 1000°C for 2 h.