Síntese e estudo de propriedades ferroicas do sistema (Bi1-x Ndx)(Fe1-yCoy)O3

Abstract

The study of crystalline multiferroic materials have great technological and academic interest due the relationship between ferroelectric and ferromagnetic properties. Among these materials, are highlighted the compounds with perovskite structures such as those BiFeO3 based. In this work ceramics with the nominal compositions (Bi1-xNdx)(Fe1-yCoy)O3 x = 0, x = 0.10, x = 0.20, y = 0, y = 0.02 e y = 0.04 were obtained by high-energy ball-milling, followed by the isostatic pressing shaping of ceramics and sintering in air atmosphere. Rapid sintering technique followed by fast cooling was also used. Through the X-ray diffraction was found that the compositions had a rhombohedral symmetry with R3c space group. Due to traces of undesired phases and relative densities around 92%, it was not possible to obtain good results in ferroelectric measurements. This was because these factors have contributed to increase the electrical conductivity of ceramics. Measurements of dielectric permittivity and loss tangent as a function of frequency and temperature showed that both factors decrease with decreasing temperature and increasing frequency. This is also related to the high conductivity of the samples. The resistivity as a function of time proved to be highly dependent on the samples' composition. Those cobalt only doped samples showed the higher resistivities. The magnetic hysteresis measurements showed that most of the samples holds an antiferromagnetic behavior.