Papers by Author: Rattikorn Yimnirun

Abstract: Hybrid-doped BaTiO₃ ferroelectric ceramics Ba (Ti_(0.99-x)Mn_0.01Ta_x)O₃ systems have been prepared by a conventional mixed-oxide method viavibro-milling technique. The dielectric properties at room temperature were observed under magnetic field applied parallel to electric field. The results indicate significant changes of both properties with the magnetic field. Moreover, explained in terms of the induction of magnetization by means of an electric field and induction of polarization according to domain switching of the dielectric properties under the influence of the applied magnetic field.

Abstract: In this study, ceramics in ((K_0.5Na_0.5)_0.935Li_0.065)NbO₃ + xMnO₂ (mol%) ceramics (when x = 0.0025, 0.0050, 0.01 and 0.015) were successfully prepared by the conventional mixed-oxide technique. The structural phase formation and microstructure were characterized by x-ray diffraction technique (XRD) and scanning electron microscopy (SEM). The crystal structure was identified by XRD as a single-phase perovskite structure, with tetragonal symmetry. The microstructure shows different grain size with different composition x. This study clearly showed that the Mn has influence on the dielectric properties in ((K_0.5Na_0.5)_0.935Li_0.065)NbO₃ ceramics.

Abstract: 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.

Abstract: Perovskite relaxor ferroelectric PMN ceramics, Pb (Mg_1/3Nb_2/3O₃), have been fabricated using a two-stage process employing a corundum-type Mg₄Nb₂O₉ as a key precursor. The 100% perovskite PMN ceramics was revealed by X-ray diffraction analysis. The SEM image of the PMN ceramic shows irregular shape PMN grains on the porous surface. The surface chemical composition of the PMN ceramics could be characterized by X-ray photoelectron microscopy technique. The XPS results indicate most of the elements consist of more than one chemical species. The important of XPS studies here can reveal small amount of species which could not detected by XRD.

Abstract: Zinc niobate, ZnNb2O6, nanopowders was synthesized by a solid-state reaction via a rapid vibro-milling technique. The effect of milling time on the phase formation and particle size of ZnNb2O6 powder was investigated. The formation of the ZnNb2O6 phase investigated as a function of calcination conditions by DTA and XRD. The particle size distribution of the calcined powders was determined by laser diffraction technique, while morphology, crystal structure and phase composition were determined via a SEM techniques. In addition, by employing an appropriate choice of milling time, a narrow particle size distribution curve was also observed.

Abstract: Ceramic solid solutions within the system (1-x)PZT-xBT, where x = 0.1, 0.2, 0.3, 0.4 and 0.5, were prepared by conventional mixed-oxide method combined with a two-stage sintering procedure. A sintering time of 2 h at 1000 °C followed by a second step in the temperature range of 1000-1200 °C for 2 h was employed to all samples and compared to the one-step sintering process. Phase formation, densification and microstructure of all ceramics were examined via X-ray diffraction (XRD), Archimedes method and scanning electron microscope (SEM). The results lead to the conclusion that the pure perovskite phase and high densification of (1-x)PZT-xBT ceramics with fine grain can be successfully achieved under suitable two-stage sintering conditions.

Abstract: In this work, the Artificial Neural Network (ANN) was used to model ferroelectric hysteresis using data measured from soft lead zirconate titanate [Pb (Zr1−xTix)O3 or PZT] ceramics as an application. Data from experiments were split into training, testing and validation dataset. Four ANN models were developed separately to predict output of the hysteresis area, remnant, coercivity and squareness. Each model has two neurons in the input layer, which represent field amplitude and field frequency. The ANNs were trained with varying number of hidden layer and number of neurons in each layer to find the best network architecture with highest accuracy. After the networks have been trained, they were used to predict hysteresis properties of the unseen testing patterns of input. The predicted and the testing data were found to match very well which suggests the ANN success in modeling ferroelectric hysteresis properties obtained from experiments.

Abstract: Perovskite ferroelectric PNN ceramics have been obtained from oxides by sintering in air, using a two-stage process with corundum Ni4Nb2O9 precursor. Under suitable firing condition, XRD analysis revealed that the ceramics consist of 100% perovskite phase. The SEM, EDX, and XPS techniques were employed to investigate the chemical composition of the surfaces of the PNN ceramics. Fluctuation in chemical composition, precipitation of NiO and the Pb-Ni-Nb-O phase different from perovskite were found.

Abstract: Effects of perpendicular compressive stress on the ferroelectric properties of ceramics in PZT-PZN system were investigated. The (1-x)Pb(Zr1/2Ti1/2)O3-xPb(Zn1/3Nb2/3)O3 or (1-x)PZT- (x)PZN (x = 0.1-0.5) ceramics were prepared by a conventional mixed-oxide method. The ferroelectric properties were measured under compressive stress applied perpendicular to an electric field direction at stress levels up to 90 MPa using a compressometer in conjunction with a modified Sawyer-Tower circuit. It was found that with increasing compressive stress the area of the ferroelectric hysteresis (P-E) loops, the maximum polarization (Pmax), and the remanent polarization (Pr) decreased, while the coercive field (Ec) remained relatively constant. These results were interpreted through the domain switching, clamping of domain walls and de-poling mechanisms.

Abstract: The scaling behavior of the dynamic hysteresis of ferroelectric BaTiO3 bulk ceramics was investigated. Two sets of the scaling relation of hysteresis area against frequency f and field amplitude E0 were clearly established. Approximately, above the coercive field, the scaling took a form of  f -0.23E00.87. On the other hand, the scaling in the form of  f -0.36E03.64 was obtained under a sub-coercive field condition. While these scaling relations were generally comparable to previously reported ones, it was found that the f- and E0 exponents clearly depended on E0 and f, respectively.