Synthesis, physical and magnetic properties of BaFe12O19/P(VDF-TrFE) multifunctional composites

Composite films with filler microparticles of Barium ferrite dispersed within P(VDF-TrFE) as polymeric matrix have been prepared by solvent evaporation. The lowest BaFO content of 1% wt acts as a small defect within the polymeric matrix, reducing the values of the dielectric and mechanical properties of the pure P(VDF-TrFE). For filler contents up to a 20%, the BaFO filler reinforces the matrix and measured properties increase their values. This trend is not followed by the electrical conductivity. We extended the study to fibers composed by BaFe12O19 microparticles in a PVDF matrix. Due to the big size of BaFO particles (1 micron in diameter), proper fabrication of the fiber shaped composites has not been achieved. We found that true BaFO content are always lower than nominal ones. Results are discussed in terms of the influence of size and morphology of the BaFO particles on the initial properties of the polymeric matrix.

Induced magnetoelectric effect driven by magnetization in BaFe12O19 -/P(VDF-TrFE) composites

Films of BaFe12O19/P(VDF-TrFE) composites with 5, 10 and 20 %wt Barium ferrite content have been fabricated. BaFe12O19 microparticles have the shape of thin hexagonal platelets, the easy direction of magnetization remaining along the c axis, which is perpendicular to the plates. This fact allows for ferrite particles orientation in-plane and out-of-plane within the composite films, as confirmed by measured hysteresis loops. While the in-plane induced magnetoelectric effect (ME) is practically zero, these composite films show a good out-of-plane magnetoelectric effect. with maximum ME coupling coefficient changes of 3, 17 and 2 mV/cm.Oe for the 5, 10 and 20%wt Barium ferrite content films, respectively. We infer that this ME behavior appears as driven by the magnetization process arising when we applied the external magnetic field. We have also measured linear and reversible magnetoelectric effect for low applied bias field, when magnetization process is still reversible.

A high order model for piezoelectric rods: an asymptotic approach

Preprint submitted to International Journal of Solids and Structures. ISSN 0020-7683