Synthesis and characterization of magnetoelectric/multiferroic ceramics
authors Marco Sílvio Assamo Medeiros
supervisors Rob Pullar; Andrei Kholkin
thesis type Mestrado
abstract Magnetoelectric and multiferroic materials that exhibit both ferroelectric and ferromagnetic properties, have raised great interest in the scientific community for the development of multifunctional materials. In this work we intended to fabricate multiferroic ceramics and to study the coupling between magnetic properties and piezoeletric/ferroelectric properties of composite materials. Synthesis of hexaferrites (BaFe12O19, SrFe12O19, Ba3Co2Fe24O41 and Sr3Co2Fe24O41), was undertaken with different reacting temperatures and different preparation methods: solid state reaction, coprecipitation, sol-gel and citrate. Also we performed analysis by XRD and determined the phases of each material. We prepared composites of hexaferrites and piezoelectric phases (BaTiO3, KNN) with uniaxial pressing and cold isotactic pressing. BaTiO3 composites have shown a relative density of 85% compared with the theoretical density and the KNN composites had a maximum density of 81%. We performed magnetic (MFM and VSM), and piezoelectric (PFM) measurements, and it was verified that in some composites we observed diffusion of atoms between barium and strontium sources producing new phases lowering the piezoelectric effect. In the magnetic analysis it also was verified that the hard ferrites formed hysteresis loops with greater area than the soft ferrites. It was found that some composites demonstrate capable magnetoelectric coupling.
year published 2013