Study of dielectric properties of lead-free multiferroic KNN/22.5 BaFe12 O19 composites

Abstract

A multiferroic (K_0.5 Na_0.5 NbO_3) -22.5% vol.(〖BaFe〗_12 O_19) composite obtained successfully by conventional sintering (abbreviated as CS) method at 1080 ℃. To compare the dielectric properties of the samples, lead-free K_0.5 Na_0.5 NbO_3 (abbreviated as KNN) piezoceramics were prepared by CS method at 1125℃. The structure and morphology have been determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and also the dielectric properties of samples were carried out. In the X-ray spectra of composite samples, all peaks related to the KNN and BFO phases, were observed without any trace of the second phase. In the SEM images of the composite, the distinct cubic morphology of the KNN phase indicating the formation of the perovskite structure of the compound, and the polygonal grains of the BFO phase were observed. The values of relative density, dielectric coefficient, and loss factor of the lead-free KNN ceramic at a sintering temperature of 1125℃ was measured to be 91%, 390, and 0.02, respectively. These values at a sintering temperature of 1080℃ were about 92%, 200 and 0.18 respectively. Although the dielectric properties of KNN-BFO composite are lower than those of pure KNN, the presence of magnetic phase can create the magnetic properties and consequently multiferroicity in the KNN-BFO composite The dielectric properties also confirm that this composite can be considered as a new multiferroic composite.