R. Wongmaneerung

Temperature scaling of dynamic hysteresis in soft lead zirconate titanate bulk ceramic

The temperature scaling of the dynamic hysteresis was investigated in soft ferroelectric bulk ceramic. The power-law temperature scaling relations were obtained for hystersis area ⟨A⟩ and remnant polarization Pr, while the coercivity EC was found to scale linearly with temperature T. The three temperature scaling relations were also field dependent. At fixed field amplitude E0, the scaling relations take the forms of ⟨A⟩∝T−1.1024, Pr∝T−1.2322, and (EC0−EC)∝T. Furthermore, the product of Pr and EC also provides the same scaling law on the T dependence in comparison with ⟨A⟩.

Dynamic hysteresis and scaling behavior of hard lead zirconate titanate bulk ceramics

The scaling relation of ferroelectric hysteresis area ⟨A⟩ against frequency f and field amplitude E0 for the saturated loops of the hard lead zirconate titanate bulk ceramic takes the form of ⟨A⟩∝f−0.28E00.89, while that for the minor loops takes the form of ⟨A⟩∝f−0.43E03.19. In both cases, the scaling relations are similar to those of its soft counterpart. This indicates that the dynamic behaviors and scaling relations in bulk ceramics are mainly governed by the domain states and structures, while the distinct types of complex defects contribute mainly to the difference in the coercive field observed in hard and soft ceramics.

Stress- and temperature-dependent scaling behavior of dynamic hysteresis in soft PZT bulk ceramics

Effects of electric field-frequency, electric field-amplitude, mechanical stress, and temperature on the hysteresis area, especially the scaling form, were investigated in soft lead zirconate titanate (PZT) bulk ceramics. The hysteresis area was found to depend on the frequency and field-amplitude with the same set of exponents as the power-law scaling for both with and without stresses. The inclusion of stresses into the power-law was obtained in the form of which indicates the difference in energy dissipation between the under-stress and stress-free conditions. The power-law temperature scaling relations were obtained for hysteresis area A and remanent polarization Pr, while the coercivity EC was found to scale linearly with temperature T. The three temperature scaling relations were also field-dependent. At fixed field amplitude E0, the scaling relations take the forms of , Pr ∝T−1.2322 and (EC0 - EC) ∝T.

Changes in ferroelectric properties of ceramics in lead magnesium niobate–lead titanate system with compressive stress

Effects of compressive stress on the ferroelectric properties of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) ceramics were investigated. The ceramics with the formula (1−x)Pb(Mg1/3Nb2/3)O3−(x)PbTiO3 or (1−x)PMN−(x)PT (x=0.1–0.5) were prepared by a conventional mixed-oxide method. Dense perovskite-phase PMN-PT ceramics with a uniform microstructure were obtained. The ferroelectric properties were measured under compressive stress (0–75 MPa) using a homebuilt compressometer in conjunction with a modified Sawyer–Tower circuit. The experimental results revealed that the superimposed compression stress significantly reduced both the dissipation energy and the polarizations of the near morphotropic phase boundary compositions, i.e., 0.8PMN-0.2PT, 0.7PMN-0.3PT, and 0.6PMN-0.4PT, while the stress influence was much less in other compositions. On the contrary, the applied compressive stress showed little or no influence on the coercive field. These results were interpreted through the non-180° ferroelastic domain switching p...

Changes in Ferroelectric Properties of 0.7PMN–0.3PT Ceramic with Compressive Stress

In this work, effects of compressive stress on the ferroelectric properties of 0.7PMN–0.3PT ceramics were investigated. The ceramics with the formula (0.7)Pb(Mg1/3Nb2/3)O3-(0.3)PbTiO were prepared by a conventional mixed-oxide method. The ferroelectric properties under compressive stress were observed at stress up to 80 MPa using a compressometer in conjunction with a modified Sawyer-Tower circuit. The results showed that applied stress had a significant influence on the ferroelectric properties of 0.7PMN–0.3PT ceramics. Ferroelectric characteristics, i.e. the area of the ferroelectric hysteresis (P-E) loop, the saturation polarization (Psat), the remanent polarization (Pr) and loop squareness (Rsq), decreased with increasing compressive stress, while the coercive field (Ec) remained relatively constant. Stress-induced domain wall motion suppression and non-180oC ferroelectric domain switching processes are responsible for the changes observed.

Effect of M-Type Hexaferrites on Mechanical and Magnetic Properties of Hydroxyapatite Ceramics

The overall aim of this study is to establish the inter-relationships between phase formations, mechanical properties and magnetic properties of the novel ceramic in hydroxyapatite system for biomaterial applications. First, barium hexaferrite and strontium hexaferrite powders were prepared as M-type hexaferrite phases. Hydroxyapatite was prepared from cockle shells via co-precipitation method. After that, a combination between hydroxyapatite+barium hexaferrite and hydroxyapatite+strontium hexaferrite was mixed together then shaping and sintering at 1200 °C for 2 h. The sintered samples were characterized phase formation, mechanical and magnetic properties by using X-ray diffraction (XRD), Universal testing and VSM measurements, respectively. XRD patterns for all samples showed a combination between hydroxyapatite and hexaferrite phases. Compressive strength of all samples tends to increase with increasing of the amount of hexaferrite phases due to densification mechanism. However, the increasing of these values, it appears that there is no difference in the statistical significant. For magnetic properties, the coexistence of barium hexaferrite and strontium hexaferrite phases reveals magnetic hysteresis loops, showing the change from diamagnetic to ferromagnetic behavior.

Synthesis Hydroxyapatite from Three Types Eggsshells by Co-Precipitation Method

In the present work, hydroxyapatite (HAp) were synthesised from three types eggshells (hen eggshells, duck eggsshells and quail eggsshells) by co-precipitation method. By using recycled eggshells, there were calcined at 700-900 °C for 2 h to form calcium carbonate (CaCO3). Then, CaCO3 and ammonium dihydrogenphosphate (NH4H2PO4) were used as precursor to produce HAp. The molar ratio of Ca to P was 1.67 : 1. In order to determine the most suitable calcination temperature to produce HAp based on purity of CaCO3, HAp were investigated over the temperatures range of 800-1100 °C for 2 h. Phase formation and microstructure evolution of HAp samples were determined by using (XRD), (SEM) and (FTIR) respectively. The results showed that CaCO3 formed at 700 °C for 2 h of all eggshell types. XRD investigations show that HAp powder were stable up to 1100 °C with hexagonal structure. SEMinvestigations demonstrate that the HAp powder obtained with a sphere morphology and FTIR confirmed that the HAp powder calcined at 1100 °C corresponded to the phosphate group in PO43- with significant characteristic peaks at 1026.5 and 563.9 cm-1.

Effect of Substitution of Zn2+ and Zr4+ on Structural and Magnetic Properties of BaFe12O19 Powders

The Zn2+ and Zr4+-doped barium hexaferrite according to the stoichiometric formation BaFe(12-(2x /3))ZnxO19 and BaFe(12-(4x /3))ZrxO19 with x = 0, 0.1, 0.3 and 0.5 were prepared by conventional method using ball milling technique. These powders were calcined at various temperatures from 1000 °C to 1200 °C for 2 h. The structural, morphology and magnetic properties were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM), respectively. The XRD confirmed the formation of main phase magneplumbite and the crystalline structure of samples is still hexagonal. Pure and dopes barium hexaferrite shows only single phase. The lattice parameter a and c increased with the Zn2+ and Zr4+ ion content increasing. The SEM results showed that the particles of pure BaFe12O19 were regular hexagonal while doped-samples showed spherical shape. After Fe3+ is partly substituted with Zn2+, the magnetic parameters like coercivity and saturation magnetization are decreased. On the other hand, with increasing Zr4+ ions, the coercive force and saturation magnetization are slightly increased. The behavior of magnetic properties of materials is explained by the combined effect of the coherent rotation of the magnetic domains and the replacements of Fe3+ by Zn2+ and Zr4+ ions in the tetrahedral and octahedral sites.

Thermal Expansion and Polarization Behavior in Lead Titanate/Zinc Oxide Nanocomposite Ceramics

Nanosized zinc oxide/lead titanate (ZnO/PT) ceramic matrix nanocomposites have been studied. Under an appropriate sintering condition, ZnO/PT ceramic nanocomposites were successfully fabricated by a pressureless sintering technique. Thermal expansion and polatization behaviors were determined by using the dilatometer. This technique measures the temperature-dependent of the strain, and the magnitude of polarization can be deduced from the sets of the thermal expansion data. The calculated electric polarization values on the ZnO/PT nanocomposite ceramics show the simple approach to determine the temperature dependence of the polarization below and around the transition temperature. Various aspects on understanding the polarization behavior and other effects in the ferroelectric are discussed.

DIELECTRIC PROPERTIES OF COMPLEX PEROVSKITE PZBT-PMNT CERAMIC UNDER COMPRESSIVE STRESS

Effects of compressive stress on the dielectric properties of complex perovskite PZBT-PMNT ceramic were investigated. The dielectric properties measured under stress-free condition showed a composite nature with two distinct temperatures of dielectric maximum associated with PZBT and PMNT end members. The dielectric properties under the compressive stress were observed at stress levels up to 230 MPa using a home-built compressometer. The results clearly showed that the compression load significantly reduced both the dielectric constant and the dielectric loss tangent in every measuring frequency. The change of the dielectric constant with stress was attributed to competing influences of the intrinsic contribution of non-polar matrix and the extrinsic contributions of re-polarization and growth of micro-polar regions, while the clamping of the domain walls contributed to the stress-dependent changes of the dielectric loss tangent. Finally, a large drop of the dielectric constant after a stress cycle was likely caused by the stress induced decrease in switchable part of spontaneous polarization.