The results of the investigations on (1 — x)PMN-xPT ceramic samples obtained by sol—gel (SG) technology are presented in this study. In the (1 — x)PMN-xPT samples, the temperature Tm (at which real part of dielectric permittivity reaches its maximum) increases from ~270 K for x = 0 to ~500 K for x = 0.5. At room temperature, the samples with low values of x exhibit relaxor properties, while with increasing x the transition to normal ferroelectric properties takes place. Usually 0.9PMN-0.1PT or 0.925PMN-0.075PT solid solutions are considered as boundary compositions between relaxor and ferroelectric properties at room temperature.This study presents the analysis of X-ray diffraction patterns, fracture microphotographs, electromechanical parameters, and hysteresis loops for ceramics obtained from SG PMN—PT powders densified by the hot pressing method with a composition range, x = 0—0.37.

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The ferroelectromagnetic Pb(Fe0.5Nb0.5)O3 (PFN) ceramic was synthesized by a powder calcining method. The aim of this work was to decrease the electric conduction of the biferroic PFN ceramic as a result of admixing it with metal oxides or carbonates. Investigation results concerning the influence of admixtures of manganese, chromium and lanthanum oxides and potassium and strontium carbonates on direct current electric conduction and dielectric parameters of the PFN ceramic are presented. Crystallographic and morphological studies were carried out using X‐ray diffraction and scanning microscopy techniques. The specimens obtained were subjected to dielectric, electric direct current conductivity, hysteresis loop and electromechanical tests. By adding small amounts of admixtures it was possible to decrease (admixtures of manganese or chromium) or increase (admixtures of lanthanum, strontium or potassium) the area of the phase transition of the PFN ceramic. It was found that admixtures of manganese and potassium decreased the electric conduction of the PFN ceramic. PFN admixed with elements of small ions, manganese and chromium, is characterized by a better set of dielectric parameters and lower dielectric losses compared to the PFN ceramic without admixtures.

The paper presents the technology of ferroelectric-ferromagnetic ceramic composites obtained from PLZT powder (the chemical formula Pb 0.98 La 0.02 (Zr 0.90 Ti 0.10) 0.995 O 3) and ferrite powder (Ni 0.64 Zn 0.36 Fe 2 O 4), as well as the results of X-ray powder-diffraction data (XRD) measurement, microstructure, dielectric, ferroelectric, and magnetic properties of the composite samples. The ferroelectric-ferromagnetic composite (P-F) was obtained by mixing and the synthesis of 90% of PLZT and 10% of ferrite powders. The XRD test of the P-F composite shows a two-phase structure derived from the PLZT component (strong peaks) and the ferrite component (weak peaks). The symmetry of PLZT was identified as a rhombohedral ferroelectric phase, while the ferrite was identified as a spinel structure. Scanning electron microscope (SEM) microstructure analysis of the P-F ceramic composites showed that fine grains of the PLZT component surrounded large ferrite grains. At room temperature P-F composites exhibit both ferroelectric and ferromagnetic properties. The P-F composite samples have lower values of the maximum dielectric permittivity at the Curie temperature and a higher dielectric loss compared to the PLZT ceramics, however, the exhibit overall good multiferroic properties.

Multiferroics with negative value of dielectric constant are very promising materials because of their modern applicability. These materials can be used as materials for the construction of electromagnetic radiation shields. The subject of the research is multiferroic BiFeO 3-PbFe 1/2 Nb 1/2 O 3 (BF-PFN) ceramics. For all multiferroic materials the following studies are conducted: SEM, EDS and the temperature dependence of dielectric constant ε′(T). Above a certain temperature (different for different chemical compositions) the value of dielectric constant reaches negative values. Such the behavior of the dielectric constant may indicate that the polarization inside the material has a reverse direction to the external electric field. That is, the electric field inside the material counteracts the applied external electric field. The obtaining materials also show negative dielectric losses. The Axelrod model is used to explain the mechanism that causes negative dielectric loss.