W. Bąk

Dielectric properties of BaTi1-xSnxO3 solid solution

Abstract The rentgenographic and dielectric properties of BaTi 1− x Sn x O 3 solid solutions were measured and analyzed as a function of Sn concentration x in room temperature. The mechanism of dielectric loss and electric polarization, involving correlation between microstructural features and dielectric ones, observed as macroscopic properties was postulated and discussed. Two dielectric loss processes were isolated for frequencies values which are Sn concentration dependent.

Controlled mechanochemical synthesis and properties of a selected perovskite-type electroceramics

This paper presents mechanochemical synthesis as an alternative to the traditional high-temperature synthesis of advanced electrotechnical ceramic materials with a perovskite-type structure. The reaction conditions for high-energy ball milling, e.g. reaction environment, energy of milling and additives to BaTiO3 such as metallic iron or zirconia from the exfoliation of the milling vessel and grinding media are discussed.

Microstructure, calorimetric and dielectric investigation of hafnium doped barium titanate ceramics

Ferroelectric properties of BaTi1− x Hf x O3 ceramics with Hf content x = 0, 0.001, and 0.025 were examined. It was found that the substitution of Hf4+ for Ti4+ in BaTiO3 resulted in shifting the two low-temperature transitions (T 1, T 2) of the investigated samples to higher temperatures and decreasing the tetragonal-cubic phase transition temperature (T c). This is a well-known pinching effect. Thermal parameters of the transitions, such as the enthalpy ΔH and the entropy ΔS, were also estimated and discussed.

Influence of Sr-Substitution on Diffuseness of (Ba1-xSrx)TiO3 Phase Transitions

The results of X-ray diffraction (XRD), scanning electron microscopy (SEM) and dielectric measurements performed for samples of the polycrystalline solid solutions of (Ba1-xSrx)TiO3, are presented. An increase of diffuseness of ferroelectric phase transition and a decrease of the temperature Tm (the temperature of the maximum value of the real part of the electric permittivity; ϵ′) with increase of Sr concentration is observed. Values of the phase angle (approximate to −90°) measured in broad range of temperatures suggest the occurrence of polar regions (clusters) in the temperature range of paraelectric (PE)-ferroelectric (FE) phase transition.

Germanium modified BaTiO3 as a promising electroceramics

ABSTRACT The polycrystalline sample of BaTi0.95Ge0.05O3 was prepared by solid-phase reaction using a conventional method. The morphology of investigated sample was characterised by scanning electron microscopy (SEM). The results allowed to determining the stoichiometry of the material and evaluate their microstructure. High quality samples were investigated, the grains are well shaped without of a glassy phase. The dielectric properties of the BaTi0.95Ge0.05O3 ceramics were determined. The results were compared with these ones obtained for pure BaTiO3. The obtained data indicated that the substitution of Ge+4 ions had an influence on the values of the real (ϵ′) and imaginary (ϵ″) parts of electric permittivity.

Electrical Characterization of the Fe-Doped BT Ceramics by an Impedance Spectroscopy

The electric properties of the Fe - doped BaTiO3 ceramics was investigated as a function of frequency and temperature. The structure and morphology of investigated sample were characterized by an X-ray diffraction and scanning electron microscopy. The impedance measurements were carried out at the temperature ranging from 450 K to 600 K, and at the frequency range from 0.1 Hz to 10 MHz. Based on these parameters the electrical properties of the grains and grains boundaries were described. The bulk and grains boundaries resistance of ceramics and the thermal activation energies were determined.

Electric properties of polycrystalline (Ba1-xSrx)(Ti1-xZrx)O3 solid solution

ABSTRACT Polycrystalline samples of (Ba1-xSrx)(Ti1-xZrx)O3 (x = 0, 0.05, 0.10) were obtained by means of a conventional high temperature technology. SEM measurements show a well-formed structure with visible layers. The increase in Sr+2 and Zr+4 ions concentration reduces the temperature of paraelectric - ferrolectric phase transition and its diffusion increases. In the paraelectric state (for all samples) the Curie-Weiss law is fulfilled. From electric modulus measurements the relaxation times and the activation energy were determined. The investigation confirmed the improvement of the electrical properties compared with polycrystalline barium titanate.

Dielectric behaviour of BaTi1-xZrxO3 ceramics obtained by means of a solid state and mechanochemical synthesis

ABSTRACT In this study the comparison of dielectric behaviour of BaTi1-xZrxO3 (BTZx) ceramic samples prepared by means of a solid state and mechanochemical synthesis was presented. A single phase of perovskite structure was identified in the samples at room temperature. No significant impurities were detected in an EDS spectrum and the samples had a good stoichiometric ratio. The morphology of the investigated samples was characterized by a scanning electron microscopy (SEM). The investigation of dielectric properties of the BTZx samples within the temperature range from 140 K to 600 K was performed by means of a dielectric spectroscopy method at the frequency ranging from 0.1 Hz to 10 MHz. The temperature dependences of real part of dielectric permittivity showed the changes of the character of the paraelectric–ferroelectric (PE–FE) phase transition for the ceramic samples obtained by means of both methods.

Preparation and Electric Properties of Barium Zirconium Titanate Ceramic

The relaxor behavior of barium zirconium titanate ceramics BaZr0.35Ti0.65O3 prepared by a conventional sintering process was investigated. The synthesized material was determined by an X-ray diffraction and scanning electron microscopy. Based on performed studies, the BaZr0.35Ti0.65O3 ceramic material has been identified as canonical relaxor, related to the Ti-rich polar regions. The freezing temperature Tf and activation energy Ea are calculated from the Vogel-Fulcher relationship.

Study of the Dielectric Properties of Europium Doped Barium Titanate Ceramics by an Impedance Spectroscopy

The barium titanate (BaTiO3) and the BaTiO3 + 0.1wt.% Eu2O3 ceramics were prepared by a conventional ceramic method. The structural studies were carried out by means of an X-ray diffraction technique. The influence of the grains and the grain boundaries on the electrical properties was investigated using a impedance spectroscopy. This technique enables us to determine the values of grain and grain boundary resistance. The results show that the Eu doping leads to a significant reduction in the resistance value of the grains (˜105Ω) with respect to the pure BT ceramics (˜107Ω). The conductivity processes were determined from the Arrhenius behaviour of grain and grain boundary resistances.