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 paper the multiferroic (ferroelectric-ferromagnetic) composites based on ferroelectromagnetic/ferroelectric (BaFe1/2Nb1/2O3 (BFN)) powder and ferrite powder (zinc-nickel ferrite) were obtained by two technological methods. In the composite samples the ratio of the ferroelectromagnetic/ferroelectric powder to the magnetic powder was equal to 90:10. The ceramic powders were synthesized by the classical technological method using powder calcination/solid state synthesis, while densification of the composite powders (sintering) was carried by two different methods: (i) Free Sintering method (FS), and (ii) Spark Plasma Sintering (SPS).
At the work, a comparison of measurement results for composite samples obtained by two sintering methods was made. The studies included the following analysis: DTA, XRD, SEM, DC electrical conductivity, electric permittivity and magnetic properties. The result of measurements presented in the work revealed that the ceramic composite obtained by two different technological sintering method (classical technology – Free Sintering method and Spark Plasma Sintering technique) can be promising lead-free materials for functional applications, for example in sensors for magnetic and electric field.
Multiferroic six-layer Aurivillius type Bi7Fe3Ti3O21 ceramics was obtained by conventional mixed oxides method. The final sintering process was taken in several different sintering times, which determined changes in properties of discussed ceramic material. The structure and dielectric properties of the material are reported. In order to examine the technological conditions on the crystal structure, XRD analysis was carried out. The microstructure, as well as the quantitative and qualitative analysis of the chemical composition were investigated by scanning electron microscope with an energy dispersion spectrometer. The main purpose of the paper is to present the effect of sintering time on the microstructure, crystallographic structure and dielectric properties of Bi7Fe3Ti3O21 ceramics.