Synthesis and Electrical Properties of 1-x(Na<sub>0.5</sub>K<sub>0.5</sub>NbO<sub>3</sub>)-x(CoFe<sub>2</sub>O<sub>4</sub>)

Abstract

Magnetoelectric (ME) effect is a coupled two-field effect in which application of an electric field induces magnetization and a magnetic field induces electrical polarization. However, it is difficult for a single material to have this combination of the ferromagnetic and ferroelectric properties. Thus, ferromagnetic–ferroelectric/dielectric composite materials become an attractive subject. Na1−xKxNbO3(NKN) is a combination of ferroelectric KNbO3and antiferroelectric NaNbO3, and forms a morphotropic phase boundary (MPB) near 50/50 composition (x=0.50) separating two orthorhombic phases. NKN has high electromechanical coupling coefficient (k2) and high phase transition temperature (Tc = 425 °C), especially near the morphotropic phase boundary (MPB). CoFe2O4(CFO), on the other hand, is well known spinel ferrite with high Curie temperature. We have synthesized ceramic composites, 1-x(Na0.5K0.5NbO3)-x(CoFe2O4) with x = 0.0 to 1.0 (in step of 0.2) by standard solid state reaction route. Powder XRD show a mixed cubic phase without impurity peaks for the samples under study. In low frequency range the dielectric properties of the NKN/CFO composites show Maxwell–Wagner relaxation. Systematic change in the electrical polarization with increasing x was observed at various applied fields at room temperature.