The structure and key functional properties of a promising lead-free solid solution, BiFeO3–BaTiO3, have been optimised by controlling chemical homogeneity via La-substitution strategies and thermal treatment.

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Polymer-based magnetoelectric composite materials have attracted a lot of attention due to their high potential in various types of applications as magnetic field sensors, energy harvesting, and biomedical devices. Current researches are focused on the increase in the efficiency of magnetoelectric transformation. In this work, a new strategy of arrangement of clusters of magnetic nanoparticles by an external magnetic field in PVDF and PFVD-TrFE matrixes is proposed to increase the voltage coefficient (αME) of the magnetoelectric effect. Another strategy is the use of 3-component composites through the inclusion of piezoelectric BaTiO3 particles. Developed strategies allow us to increase the αME value from ~5 mV/cm·Oe for the composite of randomly distributed CoFe2O4 nanoparticles in PVDF matrix to ~18.5 mV/cm·Oe for a composite of magnetic particles in PVDF-TrFE matrix with 5%wt of piezoelectric particles. The applicability of such materials as bioactive surface is demonstrated on neural crest stem cell cultures.

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The coupling between electric, magnetic and elastic features in multiferroic materials is an emerging field in materials science, with important applications on alternative solid-state cooling technologies, energy harvesting and sensors/actuators. In this direction, we developed a thorough investigation of a multiferroic composite, comprising magnetocaloric/magnetostrictive GdSiGe microparticles blended into a piezo- and pyroelectric poly(vinylidene) fluoride (PVDF) matrix. Using a simple solvent casting technique, the formation and stabilization of PVDF electroactive phases are improved when the filler content increases from 2 to 12 weight fraction (wt.%). This effect greatly contributes to the magnetoelectric (ME) coupling, with the ME coefficient increasing from 0.3 V/cm.Oe to 2.2 V/cm.Oe, by increasing the amount of magnetic material. In addition, magnetic measurements revealed that the ME-coupling has influenced the magnetocaloric effect via a contribution from the electroactive polymer and hence leading to a multicaloric effect. These results contribute to the development of multifunctional systems for novel technologies.

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A three-layer magnetoelectric composite PZT / FeRh / PZT consisting of a layer of a magnetic alloy Fe 49 Rh 51 and two layers of a piezoelectric lead zirconate PbZr 0.53 Ti 0.47 O 3 was fabricated and its magnetic properties were studied. The magnetic alloy Fe 49 Rh 51 from which the magnetic layer was made was obtained by induction melting from pure rhodium Rh (99.9 %) and iron Fe (99.98 %). An X-ray diffraction analysis of the alloy showed the predominance of a B2 type phase with a bcc structure with an impurity phase of type α' with a fcc structure. Elemental analysis confirmed the composition corresponding to Fe 49 Rh 51. Temperature dependences of magnetic susceptibility were measured in two regimes: with piezoelectric layers under voltage ("switch on") and without voltage ("switch off "). In the "switch off " regime a phase transition at 324 K in heating and at 315 K in cooling is observed that is different from the results for pure Fe 49 Rh 51. Application of a voltage to the opposite faces of the composite induces a mechanical stress on the magnetic layer that leads to a decrease in the magnetic susceptibility and shift of the transition temperatures to 320 K in heating and 316 K in cooling. Moreover, this mechanical stress changes the shape and area of the hysteresis, which can be used for control of magnetic properties of materials. The magnetic properties and temperature hysteresis with applied electric field have been theoretically considered and explained on the basis of the Landau-Khalatnikov equations.

The possibility of the formation of high entropy single-phase perovskites using solid-state sintering was investigated. The BaO–SrO–CaO–MgO–PbO–TiO2, BaO–SrO–CaO–MgO–PbO–Fe2O3 and Na2O–K2O–CaO–La2O3–Ce2O3–TiO2 oxide systems were investigated. The optimal synthesis temperature is found between 1150 and 1400 °C, at which the microcrystalline single phase with perovskite structure was produced. The morphology, chemical composition, crystal parameters and dielectric properties were studied and compared with that of pure BaTiO3. According to the EDX data, the single-phase product has a formula of Na0.30K0.07Ca0.24La0.18Ce0.21TiO3 and a cubic structure.