C. Kajtoch

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.

Dipolar polarization in Ba(Ti1−xSnx)O3

Abstract The measurements of linear expansion and remanent polarization have been performed for polycrystalline samples of Ba(Ti1−x ,Sn x )O3, (BTS-x. x = O, 0.05. 0.10, 0.20). The results obtained from the dilatometric investigations confirm the existence of the dipolar polarization Pd below 620 K, which has been previously observed in several materials.1 At the temperature of para-ferroelectric phase transition a new polarization called a cooperative polarization Pk appears. This polarization together with the oriented part of dipolar polarization—Po . contribute the observed spontaneous polarization Px . The increase of Sn substitution in BTS leads to the increase of freezing of dipolar polarization during transition to ferroelectric state.

Influence of Sn-substitution on the polar regions in Ba(Ti1-x Snx)O3

Abstract The polar regions in polycrystalline Ba(Ti1-x Snx)O3 in the temperature range 600K - Tp, where Tp is the temperature of para-ferroelectric phase transition, are independent of the content of Sn-substitution. A decrease of volume of polar regions at the increase of x leads to the rapid decrease of relative volume of ferroelectric phase below Tp. It is connected with the decrease of ferroelectric clamping and with the increase of diffuseness of para-ferroelecric phase transition in this material.

DiP228: Time dependences of dielectric constant in Ba(Ti0.95Sn0.05)O3

Abstract The time measurements of dielectric constant in polycrystalline Ba(Ti0.95 Sn0.05)O3 sample have been performed in the temperature range from 358 K to 378 K. The relaxation times Θ1 have been determined. The minimum value of Θ2 (15–30 min) and the maximum value of Θ3 (60–200 min) have been observed in the same temperature of 367.3 K. The obtained results seem to be connected with the existence of glasslike phase as well as with the stabilization of paraelectric phase.

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.

Effect of Variable Valence Ion Doping on the Dielectric Properties of BaTiO3–Based Materials

Dielectric properties of BaTiO3, BaTiO3 + 0.1 wt.% Fe2O3 and BaTiO3 + 1 wt.% Fe2O3 ceramics were studied. The dielectric measurements were performed at the temperature ranging from 130 K to 500 K and at the frequency ranging from 0.1 Hz to 10 MHz. Phase transitions were also determined by a thermal analysis in a wide temperature range. Both thermal analysis and electrical characterization techniques show that the temperature of phase transition is shifted towards lower temperatures with increasing Fe2O3 content. The changes and diversity of the observed phase transition temperatures occurred as a consequence of the ion substitution. Such behaviour of the investigated polycrystalline materials may be due to the multivalence nature of the incorporated ions.

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.