Nanopowders of ferroic oxides for magnetoelectric composites

Piezoelectric oxides are currently being considered in combination with magnetic materials for the development of magnetoelectric composites, in which stress transfer across the interface is a key issue. In this context, we report here a detailed study of the mechanochemical activation processes of the ferroelectric perovskite BiScO3-PbTiO3 and of the ferrimagnetic spinel NiFe2O4. Highly sinterable, single-phase nanopowders of both ferroic oxides are synthesised, and used for the preparation of high-density materials and two-phase composites by hot pressing. Emphasis is put on studying chemical reactions at and interdiffusion across the interface between the two phases using high spatial resolution techniques such as micro X-ray diffraction and piezoresponse force microscopy. The feasibility of preparing magnetoelectric composites by this approach is demonstrated, for which the necessity of controlling physicochemical processes at the interface is key to obtain functionality.