Lanthanum-modified BaTiO₃ electroceramic materials have superior dielectric and piezoelectric properties. Ba_0.996La_0.004Ti_0.999O₃ (BLT4) seems to be a serious candidate for ultracondensator applications. This manuscript describes the results of hafnium and europium modification of BLT 4 ceramics. The pure and doped ceramic materials were synthesized by the conventional mixed oxide method. The microstructure of obtained samples was examined by scanning electron microscope. The investigations reveal strong correlations between the presence of admixture and the grain size, which was especially visible in the case of the hafnium dopant. The frequency and temperature dielectric characteristics measurements revealed a decrease in electric permittivity. Moreover, the impedance spectroscopy investigations showed severe changes in grains and grain-boundary resistivity, which was connected with changes in electric conductivity.

The solid solution of the perovskite type structure Ba_0.996La_0.004Ti_1−yFe_yO₃ (BLTF) for varying iron content (y = 0.1−0.4 mol.%) was obtained as a result of a solid state reaction using the conventional method. At room temperature (Tr < T_C), the as-received ceramics reveals a single-phase, tetragonal structure and a P4mm space group. An increase in the iron content causes a slight decrease in the volume of the elementary cell. In addition, this admixture significantly reduces the maximum permittivity value (ε_m) and the shift of the phase transition temperature (T_C) towards lower temperatures. The BLTF solid solution shows a classical phase transition and low values of dielectric loss tangent (tgδ), both at room temperature and in the phase transition area. The Curie–Weiss temperature (T₀) and Curie constant (C) were also determined on the basis of the dielectric measurements results. The analysis of temperature changes in DC conductivity revealed presence of the positive temperature coefficient of resistivity (PTCR) effect in the phase transition area.

Multiferroic Bi7Fe3Ti3O21 ceramic materials having six perovskite-like layers were prepared by solid state reaction from simple oxides and sintered at 1263K. The microstructure and magnetoelectric properties were investigated. Based on dielectric measurements, the value of magnetoelectric coupling coefficient was figured. The magnetization as a function of temperature and magnetic field at selected temperatures was examined. Additionally, the hysteresis loop at 2 K was measured. The molar concentration of magnetic ions Fe3+ in the multiferroic Bi7Fe3Ti3O21 compound was also determined.

Pure Bi₇Fe₃Ti₃O₂₁ ceramic material and gadolinium ion (Gd³⁺)-doped ones were prepared by solid-state reaction method using simple oxides. The findings of the XRD measurements confirmed the initial author’s assumption that the dopant ions substituted in perovskite blocks influenced the dimensions of the unit cell parameters. All obtained materials are single-phase and show an orthorhombic structure with the Fm2m space group. Microstructure studies show that the admixture gadolinium doping changes the microstructure of the base material, changing grain shapes from plate-like to rounded. The temperature dependences of the electric permittivity have shown the existence of a maximum, the temperature location of which depends on both the frequency and the concentration of Gd³⁺ ions. The highest values of electric permittivity were characteristic of the material with an admixture of Gd³⁺ ions in the amount of x = 0.6 (f = 1 kHz), and the lowest values were for material with x = 0.2 (f = 1 kHz). Studies of the magnetoelectric effect have shown that the strongest coupling between magnetic and electrical properties was demonstrated by a material doped with Gd³⁺ ions in the amount of x = 0.2, for which the magnetoelectric coupling coefficient is equal to α = 12.58·10⁻⁹ s/m.

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.