Fine SrTiO₃ and Sr(Mg_0.4Ti_0.6)O_3–δperovskite ceramic powders prepared by a sol-precipitation process

Abstract

Fine $SrTiO_3$ and Sr(Mg_0.4Ti_0.6)O_3–δ powders were prepared by a sol-precipitation method. Tetraisopropyl titanate was used as a starting material, which firstly chelated with the acetic acid to form a water-soluble titanyl precursor. This precursor was then precipitated in a strong NaOH solution, to which, a nitrate solution of the required ratio of $Mg^{2 + } /Sr^{2 + }$ was also added. By properly controlling reaction conditions, high crystalline undoped and Mg-doped strontium titanates with the dominating perovskite structures could be obtained directly at 80 °C. Owing to the chelating reaction of tetraisopropyl titanate with the acetic acid, the problem of the premature hydrolysis of titanium precursor was circumvented. The rates of the hydrolysis and condensation of titanyl acylate were also diminished. The final powder obtained had a uniform particle size of 40–60 nm. The formation mechanisms of $SrTiO_3$ and Sr(Mg_0.4Ti_0.6)O_3–δ were also discussed. This study indicated that in the entire sol-precipitation process, the mixing of cations was homogeneous and the diffusion of alkaline earth cations into titanium particles occurred all at atomic level, which allowed the realization of the optimized solid-solubility in the complex oxide system. This method could be exploited for the preparation of other doped titanates.