Low-Temperature Aqueous Synthesis (LTAS) of doped (Ba,Sr)TiO3 solid solutions and related electrical properties

Among wet chemical routes, LTAS (Low Temperature Aqueous Synthesis) has been proved to be a reliable method for the preparation of nanosized powders of several Ba or Sr compounds with perovskite structure such as Titanates, Zirconates, Hafniates and Stannates. LTAS is basically grounded on the reaction solution between the chloride of the relevant Transition Metal and the Ba or Sr Hydroxide at 80 °C in a strong basic solution, under atmospheric pressure of inert gas. LTAS was applied here to the preparation of (Ba,Sr)TiO3 solid solutions doped with aliovalent elements such as La and Nb. Dopants were introduced at the very beginning of the reaction, leading to a homogeneous dispersion within the powders. Particles structure were characterised by x-ray Diffraction, morphology was observed by Electron Microscopy (TEM) and specific surface areas were measured with the BET method. All powders, crystalline, single phase, with particles size in the nanometer range, were compacted by isostatic pressing (wet bag) and sintered under various conditions. PTCR effect and Curie Temperature shift were detected. Doped samples presented a considerable increase in the room temperature dielectric constant value.