Multiferroic composites are very promising materials because of their applicability because the magnetoelectric effect occurs in them. The subject of the study were two multiferroic ceramic composites: leaded obtained from powder of the composition PbFe0.5Nb0.5O3 and ferrite powder of the composition Ni0.64Zn0.36Fe2O4 and unleaded which was obtained from the powder of the composition BaFe0.5Nb0.5O3 and the same ferrite powder Ni0.64Zn0.36Fe2O4. For the both multiferroic materials the following studies were conducted: SEM, BSE, EDS, XRD and the temperature dependence of dielectric constant ε(T). Using the previously developed method of calculating the magnetoelectric coupling factor (g), based on dielectric measurements, the magnitude of the magnetoelectric effect in the multiferroic composites was determined.
The paper presents the results of research on the influence of sintering temperature on microstructure, DC electrical conductivity, dielectric, ferroelectric and magnetic properties of PbFe1/2Nb1/2O3 ceramics doped by Li in the amount of 5.0% wt., in the abbreviation PLiFN. The ceramic samples of the PLiFN material were obtained by the two-stage synthesis – columbite method and sintered by free sintering methods. Introduction to the basic PbFe1/2Nb1/2O3 composition of the lithium admixture to decrease the electrical conductivity and reduction of dielectric loss. The tests have shown that the increase in sintering temperature orders the PLiFN ceramic microstructure, which has a positive effect on its electrophysical properties. At room temperature, the PLiFN ceramic samples show both ferroelectric and ferromagnetic properties. Considering the functional parameters of the obtained ceramic samples, the optimal technological conditions are 1100°C/2 h.
We present the results of investigations of Pb(Fe1/2Nb1/2)O3 (PFN) ceramic samples obtained using two-step synthesis (i.e. columbite method). For obtained samples complex investigations of microstructure, magnetic and electrophysical properties have been performed at low and at high temperatures. Microstructure is characterized by small grains with high homogeneity and high density (low porosity). Impedance of samples and the phase shift angle have been measured using LCR Meter. Next the AC electric conductivity, dielectric permittivity and loss tangent have been calculated. AC conductivity at frequency 3 Hz was measured in similar way using Quantum Design PPMS System in magnetic fields 1000 Oe and 10000 Oe. At temperature range 240K-260K the anomalies of conductivity are observed. These anomalies depend on measuring cycle (heating, cooling) and magnetic field.
In the work five ceramic compounds based on the (K0.44Na0.52Li0.04)NbO3 (KNLN) material modified with oxides: Cr2O3, ZnO, Sb2O3 or Fe2O3 (in an amount of 0.5 mol.%) were obtained. The KNLN-type composition powder was prepared by solid phase synthesis from a mixture of simple oxides and carbonates, while compacted of the ceramic samples was conducted by free sintering methods. In the work the effect of the used admixture on the electrophysical properties of the KNLN ceramics was presented. The XRD, EDS tests, the SEM measurements of the morphology ceramic samples, dielectric properties and DC electric conductivity were conducted. The research showed that the used admixtures introduced into the base of KNLN-type composition improve the microstructure of the ceramic samples and improve their sinterability. In the case of the dielectric measurements, it was observed a decrease in the maximum dielectric permittivity at the TC for dopred KNLN-type samples. The addition of an admixture of chromium, zinc, antimony or iron in an amount of 0.5 mol.% to the base composition (K0.44Na0.52Li0.04)NbO3 practically does not change the phase transition temperature. The diminution in the density value of doped KNLN ceramics was attributed to the alkali elements volatilization.