Study of Dielectric Properties of Lead-Free Multiferroic KNN/22.5 BaFe12O19 Composites

In the present study, a multiferroic (K0.5Na0.5NbO3)-22.5 Vol. % (BaFe12O19) composite was successfully obtained from conventional sintering (abbreviated as CS) method at 1080 °C. To compare the dielectric properties of the samples, lead-free K0.5Na0.5NbO3 (abbreviated as KNN) piezoceramics were prepared using CS method at 1125 °C. The structure and morphology were determined by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM), and the dielectric properties of samples were also investigated. 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 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 the sintering temperature of 1125 °C were measured to be 91 %, 390, and 0.02, respectively. These values at the sintering temperature of 1080 °C were about 92 %, 200, and 0.18, respectively. Although the dielectric properties of KNN-BFO composite were lower than those of pure KNN, the presence of magnetic phase could create magnetic properties and, consequently, multiferroicity in the KNN-BFO composite. The dielectric properties also confirmed that this composite can be regarded as a new multiferroic composite.