Magnetoelectric effect in piezoelectric-magnetostrictive composites

Magnetoelectric materials are potentially useful in many applications which require conversion between electrical and magnetic forms of energy. The product property of magnetoelectricity, observed in the composites of piezoelectric and magnetostrictive ceramics, was studied in composites of BaTiO{dollar}sb3{dollar} or PZT and {dollar}rm CoFesb2Osb4{dollar}. The composites with 3-0 connectivity were prepared by ball mill mixing and heterocoagulation. Multilayer composites were prepared by tape casting and cofiring the two phases. Macrocomposites were also prepared by bonding presintered samples of the two phases together with an epoxy. An experimental setup was constructed to measure the magnetically induced magnetoelectric effect.; Magnetostrictive properties of {dollar}rm CoFesb2Osb4{dollar} were observed. The hysteresis in magnetostriction was very small, which increases the useful range of the magnetic field in applications. The piezoelectric properties were much better and hence the magnetoelectric effect in multilayer samples was much larger than in ball mill mixed composites because of better poling. The magnetoelectric effect was also measured as a function of the dc magnetic bias.; The magnetoelectric voltage coefficient {dollar}alphasb{lcub}rm E{rcub}{dollar}, which is the ratio of the open circuit electric field and the applied magnetic field, in the multilayer composites, was larger than those in the composites prepared by ball mill mixing. The maximum values of {dollar}alphasb{lcub}rm E{rcub}{dollar} were 92.8 (V/m)/(kA/m) for the tape cast cofired {dollar}rm CoFesb2Osb4{dollar}-PZT4 composites and 9.55 (V/m)/(kA/m) for {dollar}rm CoFesb2Osb4{dollar}-BaTiO{dollar}sb3{dollar} (20:80 mole % ratio) ball mill mixed composites.; Theoretical models were developed to calculate the magnetoelectric voltage coefficient of 2-2 composites with different boundary conditions. Composites with 3-0 and 0-3 connectivities were modelled using a cubes model. Computer programs were developed for calculating these coefficients of BaTiO{dollar}sb3{dollar} or PZT and {dollar}rm CoFesb2Osb4{dollar} composites. The results show that 3-0 and 0-3 connectivities have a great effect on the magnetoelectric properties. If both phases have comparable dielectric constants, compliance coefficients and resistivities, then a composite with 50:50% volume fractions of the phases shows a maximum magnetoelectric effect.