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Domain Walls Motions in Barium Titanate Ceramics
1996
The shear modulus and mechanical loss at low frequencies (0.01, 0.3, 1 Hz) are measured by an inverted pendulum for BaTiO 3 ceramic with large grain sizes. The permittivity and dielectric losses are also investigated for the same material at higher frequencies between 1 and 100 kHz as function of temperature. Those results show several relaxation peaks in the ferroelectric phases. The activation energy of each peak is obtained to be 0.29, 0.45, 0.68, 0.92 eV. The influences of strain amplitude and thermal treatments are studied specially for the mechanical relaxation peak located in the tetragonal phase. All the relaxation peaks could be associated to the interaction of oxygen vacancies in …
Dielectric, thermal and Raman spectroscopy studies of lead-free (Na0.5Bi0.5)1−xSrxTiO3 (x = 0, 0.04 and 0.06) ceramics
2016
ABSTRACTLead-free (Na0.5Bi0.5)1−xSrxTiO3 (x = 0, 0.04 and 0.06) ceramics with relative densities above 97% were prepared by solid-state synthesis process. Their dielectric, thermal and Raman properties were studied. X-ray diffraction analysis shows perovskite structure with rhombohedral symmetry at room temperature. Sr doping of Na0.5Bi0.5TiO3 (NBT) results in an increase of the dielectric permittivity, diffusing of the permittivity maximum and its shift toward lower temperatures. The temperature of the rhombohedral–tetragonal phase transition indicated by the differential scanning calorimetry (DSC) peak and relaxational dielectric anomaly near the depolarization temperature are also shifte…
Relaxation of polarization in (K0.5Na0.5)(Nb0.93Sb0.07)O3 ferroelectric ceramics modified by BaTiO3
2017
ABSTRACTA study of low-frequency relaxation of polarization in conventionally prepared ceramic compounds of (1-x)(K0.5Na0.5)(Nb0.93Sb0.07)O3+xBaTiO3+0.5mol.%MnO2 (x = 0.02, 0.04) examined over a wide temperature range is reported. Anomalous behavior of the temperature dependence of the coercive field Ec(T) is detected in the temperature range of the orthorhombic to tetragonal phase transition. The observed features of polarization are assigned to dynamics of the domain structure at the temperature range of phase coexistence.
Dielectric behaviour of BaTi1-xZrxO3ceramics obtained by means of a solid state and mechanochemical synthesis
2016
ABSTRACTIn 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. …
Dielectric properties of potassium–sodium niobate ceramics at low frequencies
2016
ABSTRACTA study of the effects of ageing history on the electrical properties of lead-free ferroelectric ceramics of (K0.5Na0.5)(Nb1−xSbx)O3 + 0.5 mol% MnO2 and (K0.5Na0.5)(Nb1−xTax)O3 + 0.5 mol%MnO2 for x = 0.05 is reported. The samples after storage at a constant temperature have been subject to infra-low-frequency electric field and radiation. Differences of the photoelectric response between the two examined compounds were found and the restoration of polarisation in the aged ceramic materials by cycles of applied field is discussed.
Formation of translucent nanostructured zirconia ceramics
2021
Abstract In this work the mechanisms that affect the optical transparency of nanostructured translucent ZrO2 ceramics are studied. The translucent ceramic samples were obtained from a low agglomeration nanosized powder at low pressure and low temperature sintering. Even low pressures cause structural changes and defect creation in the nanocrystals. Annealing was used to study the grain formation, structure and impact of defects. Significant changes in translucency were observed with increase in pore size. In order to further understand the defect creation, the obtained ceramics were doped with Er3+ ions and studied optically. Photoluminescence studies revealed a change in the ratio of green…
Effect of surface disorder on the domain structure of PLZT ceramics
2017
ABSTRACTPb1-xLax(Zr0.65Ti0.35)1-x/4O3 (PLZT x/65/35) ceramics were studied by Piezoresponse Force Microscopy in order to understand the origin of domain structure as a function of La content. We show that the domain topology is mainly determined by the composition and grain size. The characteristic correlation length decreases with increasing La content, being sensitive also to the synthesis method. The behavior of the correlation length is linked to the macroscopic properties, showing a strong increase of disorder with La doping. The roughness exponent for the domain wall in PLZT 9/65/35 is close to 2/3 indicating 1D character of domain walls in relaxors.
Synergistic effect of fiber content and length on mechanical and water absorption behaviors of Phoenix sp. fiber-reinforced epoxy composites
2016
Phoenix sp. fiber-reinforced epoxy composites have been manufactured using compression molding technique. The effect of reinforcement volume content (0%, 10%, 20%, 30%, 40%, and 50%) and size (300 µm particles, 10 mm, 20 mm, and 30 mm fibers) on quasi-static and dynamic mechanical properties was investigated. Moreover, the water absorption properties of composites were analyzed at different environmental conditions (10℃, 30℃, and 60℃). For each reinforcement size, composites loaded with 40% in volume show highest tensile and flexural properties. Furthermore, composites with 300 µm particles present the best impact properties and the lowest water absorption, regardless of the environmental …
High sensitivity characterization of the nonlinear electric susceptibility of a glass ceramic in the microwave range
2019
The nonlinear electric susceptibility of a glass ceramic is characterized in the microwave range by measuring intermodulation of two high-power signals. To achieve the necessary sensitivity for dielectric nonlinearities, the setup ensures that the measured intermodulation can be ascribed to the material under test while all other intermodulation sources are suppressed. This is achieved by coupling three dielectric resonators in a cut-off waveguide. The third order nonlinearity of the glass ceramic is found to be χ3/er = (1.6 ± 0.8) × 10−15 m2/V2 at 950 MHz. The magnitude is comparable to the previously measured high-end sintered ceramics. The power of the intermodulation signal as a functio…
Quantification of relaxor behavior in (1 − x)Na0.5Bi0.5TiO3 – xCaTiO3 lead-free ceramics system
2019
Abstract This work examines the relaxor behavior of lead-free ceramic (1 − x)Na0.5Bi0.5TiO3–xCaTiO3 systems. A stable rhombohedral (R3c) phase is detected at room temperature for all compositions by XRD and Raman spectroscopy. Relaxor behavior was observed in the temperature range 300 K - 400 K for all materials. Ceramics exhibit normal ferroelectric properties at room temperature, and then they develop relaxor characteristics with increasing temperature showing the same dispersive properties. This work quantifies the relaxor phenomenon at low temperature. For instance, the maximum temperature of relaxor and the order of dispersion were determined at the strongest dispersion. Finally, the s…