Sealed-tube synthesis of BiMn2O5 materials and their physical properties have rationally been reinvestigated depending on the reactants. The aim of the study was to characterize its potential multiferroic properties and to investigate the anomalous magnetic properties in relation to the expected ferroelectric properties. Rietveld refinement of the room temperature X-ray diffraction data shows the stability of the crystallographic structure with a Mn(3+)/Mn(4+) ratio far from 1 because of bismuth and oxygen deficiencies despite the sealed-tube synthesis. Our detailed magnetic susceptibility and specific heat data analysis unambiguously support an intrinsic anomalous magnetic behavior in relation to the establishment of a magnetic short-range ordering far from the Néel temperature. Around room temperature, oxygen vacancies are responsible for supporting the dielectric loss peak measured, and, interestingly, the so-called T*, which was underlined in relation to an anomalous phonon shift (García-Flores, A. F.; et al. Phys. Rev. B 2006, 73, 104411), is not a characteristic temperature in relation to the multiferroic properties because no ferroelectric transition was detected.

Breakthroughs can be expected in multi-component ceramics by adjusting the phase assembly and the micro-nanostructure. Controlling the architecture of multi-materials at different scales is still challenging and provides a great opportunity to broaden the range of functionalities in the field of ferroelectric-based ceramics. We used the potentialities of Spark Plasma Sintering (SPS) to control a number of key parameters regarding the properties: anisotropy, interfaces, grain size and strain effects. The flexibility of the wet and supercritical chemistry routes associated with the versatility of SPS allowed designing new ferroelectric composite ceramics at different scales. These approaches are illustrated through various examples based on our work on ferroelectric/dielectric composites.

A reliable and flexible synthesis route was used for processing high density Ni-BaTiO 3 nanocable arrays based on wet chemical impregnation and subsequent electrodeposition within a highly ordered unidirectional porous alumina membrane. The core-shell structure was carefully investigated by bright field scanning transmission electronic microscopy coupled with energy dispersive X-ray spectroscopy. The strength of the dipolar interaction arising from the packing density of the magnetic nanowires was correlated with the BaTiO 3 wall thickness through magnetometry and ferromagnetic resonance measurements. Our approach opens a pathway to obtain optimized nanostructured multiferroic composites exhibiting tunable magnetic properties.