Síntese e caracterizações do BaTiO3 obtido pelo processo hidrotérmico assistido por microondas

Abstract

The present work aims the synthesis of micro or nanoparticles of BaTiO3 (barium titanate) through the microwave-assisted hydrothermal method. The BaTiO3 is a ABO3 perovskite, tetragonal structure at room temperature and is also known for its excellent dielectric, ferroelectric and piezoelectric properties, being used in dielectric capacitors, sensors, actuators and sound detectors. Aqueous solutions prepared with tetraisopropyl orthotitanate (titanium(lV) isopropoxide) (C12H28TiO4), barium acetate (C4H6BaO4) or barium chloride (BaCl2.2H2O), and potassium hydroxide (KOH) or sodium hydroxide (NaOH) were heated in a microwave oven, adapted to a temperature controller. The ceramic material was characterized from measurements of X-ray diffraction. The phase identification was carried from the indexation of the diffraction peaks with tokens international database JCPDS and indicated the formation of crystal structure of perovskite, symmetry cubic, Pm-3m space group with secondary barium carbonate phase. Network parameter values were estimated "a" from the relationship between the Bragg’s law and Müller indexes. The values of the network parameters "a" were close to those of the literature for all the samples, but without any linear relation with respect to the synthesis temperature (140 °C and 160 °C), bases (KOH and NaOH) or barium sources (C4H6BaO4 and BaCl2.2H2O). By the Scherrer’s equation it was possible to observe the formation of crystallites in a non-linear way with respect to the synthesis temperature (140 °C and 160 °C) or base used (KOH and NaOH). The only relation that can be observed is the range of crystallite size relative to the bases (KOH and NaOH). The highest yield sample among the others (BT_2.2) was synthesized with barium chloride (BaCl2.2H2O) in basic potassium hydroxide (KOH) medium at 160 °C.