This article describes the influence of thermal and dielectric properties of materials to properties of electrical insulating systems in high voltage electrical equipment. The aim of this experiment is to improve the thermal and dielectric properties of electrical insulating (composite) materials using micro fillers of aluminium oxide Al2O3. Supplement of fillers of aluminium oxide with better thermal conductivity to the electrical insulating systems can be modified to increase their thermal conductivity. Improving the thermal conductivity of electric insulation by addition of micro- or nanofillers and in the same time not adversely affecting the dielectric properties is the objective of the study. Paper is presenting the results measured on prepared samples. Improved thermal conductivity is compared with other dielectric properties as: dissipation factor temperature dependences, resistivity and dielectric spectroscopy. To determine the dielectric insulating properties the following characteristics were measured: tanδ versus temperature from 110°C to 150°C, absorption and resorption currents, volume resistivity. Furthermore, this article describes analysis of moisture and conductivity the material by dielectric spectroscopy.

Crystals of PbTiO3 and 0.9PbTiO3-0.1(Na0.5Bi0.5)TiO3 were obtained by the flux growth method whereas crystals of (Na0.5Bi0.5)TiO3 were growth by the Czochralski method. Raman spectroscopy and polarized light microscopy were performed at room temperature. The Raman spectra of 0.9PbTiO3-0.1(Na0.5Bi0.5)TiO3 shown significant changes comparing to the base materials PbTiO3 and (Na0.5Bi0.5)TiO3. A domain structure was investigated by use polarized light microscopy. Dielectric permittivity measurements were carried out in the temperature range from 20°C to 550°C and a frequency from 1 kHz to 1 MHz. These showed higher dielectric permittivity for the crystals 0.9PbTiO3-0.1(Na0.5Bi0.5)TiO3 than the source materials PbTiO3 and (Na0.5Bi0.5)TiO3.

The high value of dielectric constant makes it possible to applied 0.9PbTiO3-0.1(Na0.5Bi0.5)TiO3 as efficient dielectric medium in a capacitors. The small size of the domain structure with the easy possibility of switching by application of an external electric field, give opportunities to apply these materials to FRAM memory applications. Moreover, the high sensitivity of these materials to the surrounding gases e.g. ammonia, chlorine, hydrogen, etc., allows the construction of sensor devices.

Polycrystalline samples BaTiO3 and the solid solutions Ba0.9Sr0.1TiO3, Ba0.9Sr0.1Ti0.9Sn0.1O3, Ba0.9Sr0.1Ti0.8Sn0.2O3 were obtained by means of a mechanochemical treatment based on the high-energy ball milling technique and next a high temperature solid state reaction method. The influence of synthesis condition on microstructural, dielectric and ferroelectric properties of obtained solid solutions were investigated. The structure and morphology of the investigated samples were characterized by an X-ray diffraction (XRD) and scanning electron microscopy (SEM). The characterization of electrical properties of the ceramics within the temperature range from –130°C to 250°C were performed by means of a dielectric spectroscopy method at the frequency ranging from 0.1 Hz to 10 MHz. The diffusion of the paraelectric – ferroelectric phase transition and dielectric relaxation for ceramic samples are described.

This paper presents the results of obtaining and investigations of Pb1–xBax(Zr1–yTiy)1–zSnzO3 (PBZTS) ceramics with constant x = 0.03 and y = 0.02, and variable z = 0, 0.04, 0.06 and 0.08 (abbreviations of the samples were following PBZTS0, PBZTS4, PBZTS6, PBZTS8, respectively). The investigated compositions are close to rhombohedral-orthorhombic morphotropic phase boundary. The ceramic samples have been obtained by conventional ceramic technology from simple oxides PbO, ZrO2, TiO2, SnO2 and barium carbonate BaCO3. The ceramic powders, after calcination, have been pressed into discs and sintered using free sintering (FS) method. For samples obtained in such a way, the dielectric properties at various frequencies and electrical conductivity have been investigated. The increase of Sn content orders the microstructure of ceramics, and as a result the improvement of the dielectric properties of ceramic samples can be obtained.

Lead-free ceramics of Na0.5K0.5Nb1-xSbxO3 (NKNS) and Na0.5K0.5Nb1-xSbxO3 + 0.5 mol%MnO2 (NKNS + 0.5 mol%MnO2) (0 < x < 0.06) ceramics were prepared by a conventional solid-state hot pressing method. The ceramics possess a single-phase perovskite structure with orthorhombic symmetry. Microstructural examination revealed that Mn doping of NKNS leads to improvement of densification. The cubic-tetragonal and tetragonal-orthorhombic phase transitions of NKNS shifted to higher and lower temperature, respectively after introduction of Mn ion. Besides, ferroelectric and piezoelectric properties were improved. The results were discussed in term of difference in both ionic size and electronegativity of Nb5+ and Sb5+ and improvement of densification after Mn ion doping.

Aurivillius Bi5Ti3FeO15 (BTF) and Bi5-xNdxTi3FeO15 (BNTF) ceramics were successfully synthesized by a simple solid state reaction method. Ceramics were prepared from simple oxide powders Bi2O3, TiO­2, Nd2O3 and Fe2O3. The microstructure, structure, chemical composition and dielectric properties of the obtained materials were examined. Dielectric properties were investigated in a wide range of temperatures (T = 25ºC-550ºC) and frequencies (20Hz-1MHz).

Aurivillius Bi5-xHoxTi3FeO15 (BHTFO) multiferroic ceramics with different holmium doping contents were synthesized by conventional solid state reaction. The effect of holmium doping on the microstructure, structural and dielectric behaviors of BHTFO ceramics were investigated in details. Microstructure and crystalline structure studies of ceramics were carried out at room temperature while dielectric properties were investigated in a wide range of temperature (T = 25ºC-550ºC) and frequency (20Hz-1MHz).

In the present study, the lead-free BaTi1-xZrxO3 (for x = 0, 0.05 and 0.15) ceramics were prepared by High-Energy Ball Milling and heat treatments. The performed X-ray, SEM and EDS measurements confirmed high purity, good quality and the expected quantitative composition of the obtained samples. The study of dielectric properties was performed by means of broadband dielectric spectroscopy at the frequency ranging from 0.1 Hz to 10 MHz. The obtained measurement data, analyzed in accordance with the Arrhenius formalism demonstrated the presence of relaxation type dielectric mechanisms. The impedance answer of studied ceramic materials indicated the presence of two relaxation processes: one with a dominant resistive component and the other with a small capacitive component. The observed dielectric relaxation process is temperature dependent and has a “non-Debye” character.

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.