Preparation of BaTiO3 and other perovskite-like compounds via low-temperature aqueous synthesis (LTAS)

Powders of perovskite-like compounds can be obtained, often in the crystalline form, by an aqueous synthesis performed at low temperature (80 degrees C) under atmospheric pressure (LTAS). The reaction between Ba(OH)(2) and TiCl4 to form BaTiO3 was carried out at pH>13 in a batch reactor under a N-2 stream. This procedure was extended to other systems and, accordingly, compounds with general form MXO3, where M = Ba or Sr and X = Ti, Zr, Hf. For X = Sn the reaction gives rise to MSn(OH)(6) which turns into the perovskite compounds after thermal treatment at T>300 degrees C. The synthesis of BaTiO3 starting from TiCl4 aqueous solutions was also studied, as an easier manipulation and the possibility of introducing dopants (La3+, Nb5+...) directly during the reaction can be achieved. Influence of TiCl4 concentration on the final product has been observed. Raman spectroscopy gives account for different species in solution responsible of possible different reactions leading to polytitanates formation. Particle size was mainly affected by [Ba2+] concentration and aging time after precipitation. After sintering, measurements of electrical permittivity, loss factor and resistivity were carried out