Obtaining and main dielectric properties of Ba0.6Pb0.4TiO3/graphene oxide composite

The paper describes the technology of obtaining and the results of the investigations of microstructure, XRD, SEM, main dielectric properties, electrical conductivity measurements and P-E hysteresis loops of Ba0.6Pb0.4TiO3/graphene oxide composite (abbr. BPT/GO). In the final step of the technology, the samples have been sintered using the Spark Plasma Sintering (SPS) method. Diffraction patterns of the BPT/GO composite exhibit lines which can be related to perovskite structure. They also reveal additional lines that can be derived from the initial component oxides. Investigations of electrical conductivity suggest that the positive temperature coefficient of resistivity (PTCR) effect occurs at temperatures up to approximately 120 °C. Dielectric hysteresis loops below 90 °C are wide and typical for materials with rather high electrical conductivity. The hysteresis loop obtained at 120 °C is more typical for ferroelectrics. The obtained material is interesting, nevertheless it is probably possible to find better conditions of obtaining and/or a better composition thereof.

Characterization of PTC effect in BaTiO3-ceramics as a special phase transition - fractal approach

The applications of BaTiO3-ceramics are very important and constantly increasing nowadays. In that sense, we analyzed some phenomena related to intergranular effects. We used experimental data based on Murata powders and processing technology. Our original contribution to Heywang-Jonker-Daniels inter-granular capacity model is based on thermodynamic fractal analysis applied on phase transition in ceramic structures. In this case, PTCR effect has a diffuse first-order phase transition character in a modified Landau theory-fractal approach. Its basic properties are considered. This is an original contribution as a bridge between theoretical aspects of BaTiO3-ceramics and experimental results.

Dielectric and Electrical Properties of BLT Ceramics Modified by Fe Ions

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.

Obtaining and Main Dielectric Properties of Ba0.6Pb0.4TiO3/graphene Oxide Composite

In this paper there is described the technology of obtaining and results of investigations of microstructure, XRD, SEM, main dielectric properties, electrical conductivity measurements and P-E hysteresis loops of Ba0.6Pb0.4TiO3/graphene oxide composite (abbr. BPT/GO). In the final step of technology, the samples have been sintered using the Spark Plasma Sintering (SPS) method. Diffraction patterns of BPT/GO composite exhibit lines which can be related with perovskite structure, as well as reveal additional lines that can be derived from the initial component oxides. Investigations of electrical conductivity suggest that the PTCR effect occurs at temperatures up to about 120°C. Dielectric hysteresis loops below 90°C are wide and typical for materials with rather high electrical conductivity. The hysteresis loop obtained at 120°C is more typical for ferroelectrics. The obtained material is interesting, however it is probably possible to find better conditions of obtaining it and/or a better composition.

Defect chemistry of donor-doped BaTiO3 with BaO-excess for reduction resistant PTCR thermistor applications – redox-behaviour

The electrical conductivity of donor-doped BaTiO3 thermistor ceramics with excessive BaO revealing a reduction-persistent PTCR effect has been carefully examined depending on materials’ composition and oxygen partial pressure at moderate temperatures between 973 and 1273 K.

High-Temperature Dielectric Relaxation Behaviors in Mn3O4 Polycrystals

High temperature dielectric relaxation behaviors of single phase Mn3O4 polycrystalline ceramics prepared by spark plasma sintering technology have been studied. Two dielectric relaxations were observed in the temperature range of 200 K–330 K and in the frequency range of 20 Hz–10 MHz. The lower temperature relaxation is a type of thermally activated relaxation process, which mainly results from the hopping of oxygen vacancies based on the activation energy analysis. There is another abnormal dielectric phenomenon that is different from the conventional thermally activated behavior and is related to a positive temperature coefficient of resistance (PTCR) effect in the temperature region. In line with the impedance analyses, we distinguished the contributions of grains and grain boundaries. A comparison of the frequency-dependent spectra of the imaginary impedance with imaginary electric modulus suggests that both the long range conduction and the localized conduction are responsible for the dielectric relaxations in the Mn3O4 polycrystalline samples.

Influence of Ba/Ti ratio on PTCR effect of Bam(Ti1−xNbx)O3 ceramics prepared by the reduction sintering-reoxidation method

In this work, we investigate the influences of Ba/Ti ratio and sintering conditions on the characteristics of positive temperature coefficient of resistance (PTCR) and electrical properties of Ba[Formula: see text](Ti[Formula: see text]Nb[Formula: see text])O3 (BTN) ceramics. The ceramics were fired at 1190[Formula: see text]C for 0.5–6.0 h in a reducing atmosphere and then reoxidized at 600–650[Formula: see text]C for 0–8 h. The Ba/Ti ratio [Formula: see text] affected the electrical properties and PTCR effect of the BTN specimens. The room-temperature (RT) resistance of the BTN samples initially decreased [Formula: see text] and then increased [Formula: see text] as the Ba/Ti ratio increased. Moreover, BTN ceramics exhibit a pronounced PTCR effect, with a resistance jump greater by 3.0 orders of magnitude and a low 0.1 [Formula: see text] RT resistance at a low reoxidation temperature of 600[Formula: see text]C after sintering under a reducing atmosphere. Furthermore, the average sample grain size increased along with the Ba/Ti ratio. In addition, the influence of the sintering time and the reoxidation time on the electrical properties and the PTCR effect were also investigated.