The solid solution of the perovskite type structure Ba0.996La0.004Ti1−yFeyO3 (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 < TC), 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 (εm) and the shift of the phase transition temperature (TC) 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.

No abstract

The results of fabrication process and characterization of Bi1-xGdxFeO3 (x = 0.05, 0.07, 0.10) ceramics are reported in the paper. The samples were prepared by standard solid state reaction method from the mixture of oxides: Bi2O3, Fe2O3 and Gd2O3. The influence of Gd substitution on the microstructure and density of Bi1-xGdxFeO3 was studied. Phase composition and structure of the obtained samples were investigated by Xray diffraction. It turns out that the Bi1-xGdxFeO3 solid solutions with x = 0.05 and 0.07 crystallize in trigonal structure characteristic of BiFeO3 compound. For the sample with x = 0.1, beside the major trigonal phase, 6% of orthorhombic phase typical for GdFeO3 was detected. Hyperfine interaction parameters were studied by M?ssbauer spectroscopy. M?ssbauer results proved that the spin cycloid characteristic of BiFeO3 compound gradually disappears when substituting Gd3+ ions at the Bi3+ sites.

Multiferroic Bi 7 Fe 3 Ti 3 O 21 ceramic materials having six perovskite-like layers were prepared by solid state reaction from simple oxides and sintered at 1263 K. 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 Fe 3+ in the multiferroic Bi 7 Fe 3 Ti 3 O 21 compound was also determined.

Lanthanum-modified BaTiO3 electroceramic materials have superior dielectric and piezoelectric properties. Ba0.996La0.004Ti0.999O3 (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.