Magnetoelectric Properties of BiScO3-PbTiO3/NiFe2O4 Ceramic Composites

Abstract

Piezoelectric oxides are being considered in combination with magnetic materials for the development of magnetoelectric two-phase composites, in which strain continuity across the interface is a key issue [1]. In this context, we are investigating novel methods for the preparation of ceramic composites that minimize phase interdiffusion and reactions during material preparation [2]. Novelty rests on using nanopowders of the ferroic oxides obtained by mechanosynthesis, and the spark plasma sintering (SPS) to obtain laminated composites. We have chosen the morphotropic phase boundary BiScO3-PbTiO3 perovskite because it shows highpiezoelectric coefficients comparable to those of Pb(Zr,Ti)O3, with a higher Curie temperature, and better properties on grain size down-scaling [3]; and the NiFe2O4 spinel as the magnetostrictive phase. Fig. 1 shows a FEG-SEM image of the typical multilayer composite obtained by SPS with layers of 35-50m prepared by tape-casting. Emphasis has been put on minimizing chemical reactions at and interdiffusion across the interface between the two phases to obtain dense composites with tailored interfaces. Interfaces were further investigated by using high spatial resolution techniques such as micro-RAMAN and piezoresponse force microscopy (PFM). The macroscopic electrical, magnetic and magnetoelectric properties are described, as shown in Fig. 1 for the latter case. A novel equipment, recently designed and implemented at ICMM, was used to characterize the magnetoelectric response. Results are correlated with the interface characteristics, and demonstrate the feasibility of preparing magnetoelectric composites by this approach.