The nanoscale coating of particles of a material with a dissimilar compound is an effective tool to engineer its surface, microstructural characteristics and functional properties. The method of using coreshell powders followed by an appropriate method of sintering is a very successful route to obtain desired microstructures with various degrees of connectivity in ceramic composites. Core-shell multiferroic formed by a magnetic core (Fe2O3 and (Ni,Zn)Fe2O4) and a ferroelectric shell (BaTiO3) were prepared and then densified either by classical sintering at various temperatures (10500 C- 11500 C) or by spark plasma sintering [1]. By employing various sintering strategies, dense and homogeneous ceramics were produced with: (i) di-phase compositions with fully isolated magnetic regions within a BaTiO3 matrix (0-3 connectivity), (ii) multi-phase compositions, as result of the interface reactions between constituents. Besides the properties of the parent materials, variable amounts of secondary phases (Fe3O4, BaFe12O19 and Ba12Fe28Ti15O84) have driven to new functional properties in the ceramic composites. Dielectric, tunability and magnetic properties were determined and discussed in correlation with the sample microstructures, composition and degree of connectivity. The ceramics show interesting dielectric characteristics, with dielectric constant of 100-300 (Fig. 1 a) and low losses by comparison with other BaTiO3-based magnetoelectric composites due to the isolation of the low-resistivity magnetic phase [2]. Peculiar magnetic properties, including "waspwaisted" constricted M(H) loops were determined as result of the formation of magnetic phases with contrasting magnetic coercivities (hard and soft phases) (Fig.1 b, c). The present results demonstrate the usefulness of the core-shell approach in driving new functional properties in multifunctional composites by an appropriate control of the in situ solid-state nanoscale interface reactions.
New functional properties driven by interface reactions in core-shell structures
MT Buscaglia;VBuscaglia;
2013
Abstract
The nanoscale coating of particles of a material with a dissimilar compound is an effective tool to engineer its surface, microstructural characteristics and functional properties. The method of using coreshell powders followed by an appropriate method of sintering is a very successful route to obtain desired microstructures with various degrees of connectivity in ceramic composites. Core-shell multiferroic formed by a magnetic core (Fe2O3 and (Ni,Zn)Fe2O4) and a ferroelectric shell (BaTiO3) were prepared and then densified either by classical sintering at various temperatures (10500 C- 11500 C) or by spark plasma sintering [1]. By employing various sintering strategies, dense and homogeneous ceramics were produced with: (i) di-phase compositions with fully isolated magnetic regions within a BaTiO3 matrix (0-3 connectivity), (ii) multi-phase compositions, as result of the interface reactions between constituents. Besides the properties of the parent materials, variable amounts of secondary phases (Fe3O4, BaFe12O19 and Ba12Fe28Ti15O84) have driven to new functional properties in the ceramic composites. Dielectric, tunability and magnetic properties were determined and discussed in correlation with the sample microstructures, composition and degree of connectivity. The ceramics show interesting dielectric characteristics, with dielectric constant of 100-300 (Fig. 1 a) and low losses by comparison with other BaTiO3-based magnetoelectric composites due to the isolation of the low-resistivity magnetic phase [2]. Peculiar magnetic properties, including "waspwaisted" constricted M(H) loops were determined as result of the formation of magnetic phases with contrasting magnetic coercivities (hard and soft phases) (Fig.1 b, c). The present results demonstrate the usefulness of the core-shell approach in driving new functional properties in multifunctional composites by an appropriate control of the in situ solid-state nanoscale interface reactions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
