We report a novel strategy to improve the dielectric properties of the biferroic YCrO3 ceramic compound through interface conduction control by means of an insulating Al2O3 using a core‐shell design. The YCrO3 particles were covered with several layers of insulating Al2O3 using the atomic layer deposition technique to produce the core‐shell structure. TEM images reveal homogeneous and well‐defined Al2O3 coatings of ~8, ~60, and ~130 nm thickness. XRD shows the Al2O3‐shell to be amorphous. The dielectric characteristics of the sintered nano‐composite were investigated in the 100 Hz–1 MHz frequency range and temperature between 300 and 580 K. As the Al2O3‐shell thickness covering the YCrO3 particles is increased, a decrease of the dielectric permittivity, loss tangent and AC conductivity values was found in the whole range of temperatures and frequencies. Furthermore, the rounded hysteresis loop, typical of conductive ceramic is restored as the insulating Al2O3 layer becomes thicker. This behavior is explained because the insulating Al2O3‐shell acts as internal barrier layer localizing the surface charges on the sintered grain boundaries. This fact was confirmed by Electron Beam Induced Current technique where a clear contrast at the grain boundaries confirms the charge localization at the YCrO3/Al2O3 interface. These results also reveal that the Al2O3‐shell induces another conductive mechanism when the insulating Al2O3 layer becomes thicker. Nonetheless, this new strategy is an effective approach to suppress the parasitic conductivity in polycrystalline multiferroic ceramics and increasing thus the multifuncionality.

Core-shell YFeO 3 @Al 2 O 3 structure was obtained using advanced synthesis process. YFeO 3 @Al 2 O 3 assemble was achieved by coating individual YFeO 3 particles with several nanometers thickness of alumina-shell. After that, the particles characterization and the thickness control of the magnetic core/alumina interface were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Finally, the magnetic properties of the resulting system were investigated. We found that the alumina-shell thickness diminishes the magnetization values and enhance the exchange bias effect at low magnetic field. This fact is explained by the pinning the weak ferromagnetic and antiferromagnetic domains wall motion at the interface of the core/shell during the descending and ascending magnetization in the hysteresis curves. The results prove that the weak-ferromagnetic and the antiferromagnetic ordering not only coexist but also they are weakly coupled in YFeO 3 .