Síntese e caracterizações de BaTi(1-x)Fe(x)O3 obtido pelo método hidrotérmico assistido por micro-ondas

Abstract

The present work aims at the synthesis of BaTi(1-x)Fe(x)O3 (x = 0.00; 0.01; 0.05 and 0.15), through the microwave-assisted hydrothermal method. BaTiO3 is an ABX3 type perovskite, with 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. The addition of Fe in the lattice leads to the replacement of Ti4+ ions by Fe3+, leading to a decrease in Curie temperature, reduction in the dielectric constant, reduction in the gap energy and favors ferromagnetic properties. Aqueous solutions were inserted into microwave- assisted hydrothermal synthesis equipment. Samples were characterized by X-ray diffractometry, micro-Raman spectroscopy and UV-Vis spectroscopy. The diffractograms and micro-Raman spectra reveal a coexistence of phases with (1) cubic and tetragonal symmetry, with space group Pm-3m and P4mm at x = 0.00 and 0.01; and (2) cubic symmetry and Pm-3m space group at x = 0.05 and 0.15, all of them without a formation of secondary phases. Values of the lattice parameter "a" were estimated and an increase in the lattice parameter between the pure sample and 1% Fe is observed. The average crystallite size presented estimated values of 46 nm for at 0.00 ≥ x ≥ 0.05 and of 56 nm at x = 0.15; representing a 20% increase over the pure sample. The band gap values also a reduction due to the addition of Fe, which is related to the replacement of Ti4+ ions by Fe3+ ions, which caused the creation of oxygen vacancies for stoichiometric compensation due to the breaking of Ti-O bonds. Paramagnetism was observed in BaTi(1-x)Fe(x)O3 at 0.00 ≥ x ≥ 0.05 while at x = 0.15 exhibits weak ferromagnetism with low coercivity and small remanence, showing maximum values of saturation magnetization Ms ~ 1.29 emu/g, remanence Mr ~ 0.14 emu/g and coercivity Hc~ 0.13 kOe.