Study of Bi_0.5Na_0.5TiO₃ (BNT) system doped with lanthanum (La³⁺) obtained by acetic acid route in sol-gel process

This work studies the Bi0.5Na0.5TiO3 (BNT) system doped with lanthanum (La3+) at molar concentrations 0.0, 0.3, 0.6, 0.8, 1.0, 3.0 and 6.0 . The samples were synthesized by the Sol-gel method using the acetic acid route. The bulk samples were calcined at 700 ºC/1hr seeking to obtain the perovskite phase, and finally the samples were sintered at 1050 ºC/1hr, with density values between 90 and 92% with respect to the theoretical density. The La doping effect in the BNT system was analyzed using X-ray diffraction (DRX), Scanning electron microscopy (SEM), Ferroelectric hysteresis curves and Raman spectroscopy. The samples show a crystalline rhombohedral structure and a decreasing behavior of the grain size for La concentrations greater than 0.3%. After the incorporation of 0.6% of lanthanum concentration the presence of the pyrochlore phase of Bi2Ti2O7 is appreciated. The best ferroelectric properties were obtained for BNT doped with lanthanum (La3 +) at 6% in which a rhombohedral structure and traces of pyrochlore phases were obtained. This sample presented a maximum polarization (Pm) of 22.55 µC/cm2, remnant polarization (Pr) of 22.06 µC/cm2 and a coercive field (Ec) of 25 kV/cm.

Keywords: Ferroelectric ceramics, piezoelectrics, multifunctional materials.