Boonruang Marungsri

Investigation of the Unit Cell Distortion in PZT Ceramic via in-situ XAS Technique

Lead zirconate titanate ceramics, PZT, is a perovskite material that shows a great piezoelectric/ferroelectic effect. This phenomenon is caused by the shift of Ti4+ or Zr4+ ion relative to neighboring atoms. Such movement results in the change of the spontaneous polarization direction known as domain switching. Microscopically, the switching behavior due to the movement of the ions can be analyzed by using X-ray absorption near-edge structure (XANES). The aim of this project is to elicit the relationship between switching behavior and local/unit cell distortion in PZT ceramic under the application of electric field employing X-ray absorption technique. In this experiment, PZT sample was subjected to 0.7 kV/mm and 1.4 kV/mm respectively. The Ti K-edge X-ray absorption spectra reflect the change of the local structure of the unit cell of PZT specimens before and after electrical static loading. The result shows that the XANES spectra intensity changes when the electrical load was applied. This can be caused by the shift of Ti atoms in the unit cells. The experiment result is in agreement with the simulation result obtained from ATOMS (version 2.50) and FEFF (version 8.20) software.

SOLVING THE UNIT COMMITMENT PROBLEM USING AN ADAPTIVE IMMUNE GENETIC ALGORITHM

This paper presents an Adaptive Immune Genetic Algorithm (AIGA) solution to solve the Unit Commitment (UC) problem. The unit commitment problem formulation takes into consideration the minimum up and down time constraints, start up cost and spinning reserve, which is defined as the minimization of the total objective function while satisfying all the associated constraints. Mathematical formulation, illustration and production results for a 10 generator‐scheduling problem are presented. Finally, numerical results of systems are established the effectiveness of purpose technique.

Polarization Switching of PZT under Electrical Field via in-situ Synchrotron X-ray Absorption Spectroscopy

Lead zirconate titanate (PZT) ceramics have been extensively used for electronic applications due to their ability to couple mechanical and electrical energy, a so-called piezoelectric effect. This effect is caused by the shift of Ti4+ or Zr4+ ion relative to neighbouring atoms. The movement of the ions due to an external load causes reorientation of the ferroelectric polarization. Microscopically, the detail of the shift of Ti ion, reflecting polarization switching behaviour, can be analyzed by X-ray absorption near-edge structure (XANES) technique. The aim of this project is to investigate the shift of Ti4+ ion in PZT under the application of electric field by in-situ X-ray absorption technique. For this project, the special custom-built high voltage sample chamber installed at synchrotron XANES beam line at Synchrotron Light Research Institute, Thailand, was employed to conduct the experiment. XANES spectrum of bulk PZT was collected under the different amplitudes of an applied electric field. Ti K-edge X-ray absorption spectra were analyzed by IFEFFIT software package. The results showed that the pattern of XANES changed with the alternation of the applied field amplitude. The change of XANES spectrum was caused by the movement of Ti4+ ion reflecting the change of ferroelectric polarization. From the analysis, it was found that this technique could be used to investigate the Ti4+ ion shifting of PZT bulk ceramics.

Effect of Heat Treatment on Aging Degradation of the Piezoelectric Properties of Lead Zirconate Titanate

The aging degradation of the piezoelectric properties of lead zirconate titanate (PZT) was investigated at different heat treatment temperatures (30 to 80% of Curie temperature (TC)). The aging degradation behavior was represented by the decrease of piezoelectric charge coefficient (d33 ) and electromechanical coupling factor (k). The results showed that the degree of aging degradation of piezoelectric properties increased with increasing heat treatment temperature. The aging degradation was more pronounced when the heat treatment temperature was greater than 50% of TC. These results can be applied to predict the aging rate of electronic devices containing a PZT component.

OPTIMAL PID TUNING FOR POWER SYSTEM STABILIZERS USING ADAPTIVE PARTICLE SWARM OPTIMIZATION TECHNIQUE

An application of the intelligent search technique to find optimal parameters of power system stabilizer (PSS) considering proportional‐integral‐derivative controller (PID) for a single‐machine infinite‐bus system is presented. Also, an efficient intelligent search technique, adaptive particle swarm optimization (APSO), is engaged to express usefulness of the intelligent search techniques in tuning of the PID—PSS parameters. Improve damping frequency of system is optimized by minimizing an objective function with adaptive particle swarm optimization. At the same operating point, the PID—PSS parameters are also tuned by the Ziegler‐Nichols method. The performance of proposed controller compared to the conventional Ziegler‐Nichols PID tuning controller. The results reveal superior effectiveness of the proposed APSO based PID controller.

Investigation of the effect of temperature on aging behavior of Fe-doped lead zirconate titanate

The aging degradation behavior of Fe-doped Lead zirconate titanate (PZT) subjected to different heat-treated temperatures was investigated over 1000h. The aging degradation in the piezoelectric properties of PZT was indicated by the decrease in piezoelectric charge coefficient, electric field-induced strain and remanent polarization. It was found that the aging degradation became more pronounced at temperature above 50% of the PZT’s Curie temperature. A mathematical model based on the linear logarithmic stretched exponential function was applied to explain the aging behavior. A qualitative aging model based on polar macrodomain switchability was proposed.

Effect of Temperature on Ferroelectric and Piezoelectric Behaviour of Mn-Doped 0.75BF-0.25BT Multiferroic Ceramics

The effect of temperature on ferroelectric and piezoelectric behaviour of multiferroic ceramics (1 mol% Mn-doped 0.75BF-0.2BT) was investigated under an electric field at various temperatures (30 to 200°C). The polarization hysteresis loop and strain loop of ceramics were investigated at various temperatures. The effect of temperature was represented by the change of polarization hysteresis loop, strain loop and dielectric properties with various temperatures. The results showed that the remanant polarization and remanant strain of ceramics were improved with increasing temperature. The improving of these properties could be attributed to the greater domain switch ability at high temperature.

Effect of Temperature on Ferroelectric Properties of Bismuth Ferrite-Barium Titanate

The effect of temperature on ferroelectric properties of the 1 mol% Mn-doped 0.75BF-0.25BT ceramic was investigated under an electric field at various temperatures (−20 to 200°C). An electric field (sine wave) of 52 kV/cm at 50 Hz was applied to the sample. The effect of temperature was represented as the changed of polarization hysteresis loop and dielectric properties with various temperatures. The results show that the polarization hysteresis loops increase with increasing temperature because of greater domain switchability at higher temperature. Dielectric loss and dielectric constant increase with increase temperature and tend to decrease with increasing frequency. The samples break down at higher temperature due to the strong leakage current density, which may be caused by an increase in the activity of the free carries.