Smart Materials

Paper Title Page

Authors: Paisan Setasuwon, S. Kijamnajsak
Abstract: Na0.5Bi0.5TiO3 is one of the potential candidates for non-lead piezoelectric materials to replace existing lead-based ones. Properties of BNT could be enhanced by reactive templated grain growth (RTGG) technique through induction of grain orientation with crystals of Bi4Ti3O12. Controlling the size of Bi4Ti3O12 crystals during the synthesis with molten salt is a major factor in optimizing RTGG. It was found that molten salt synthesis of Bi4Ti3O12 crystals with NaCl-KCl yielded larger particles, compared with Na2SO4-3K2SO4. Varying the proportion of chloride salt did not produce noticeable changes in crystal size. Bi4Ti3O12 crystals were significantly affected by raw materials treatment. Non-milling of starting powders could approximately double the crystal size
165
Authors: Panadda Sittiketkron, S. Sukkho, Theerachai Bongkarn
Abstract: In this work, the effect of ZrO2 doping on the properties of PbTiO3 ceramics was investigated. PbTiO3 powders were prepared via a mixed oxide method with a calcination temperature of 750 °C for 2 h. The various amounts of ZrO2, between 0 and 2 wt.%, were added to the calcined powders to decrease the c/a ratio. The mixed powders were sintered at 1225 °C for 2 h. The samples were characterized using X–ray diffractrometer (XRD), scanning electron microscopy (SEM) and differential scanning calorimeter (DSC). It was showed that the ZrO2 phase was not detected in all of the powder and ceramic samples. The highest density in the ceramics was found in the sample with 0.5 wt.% of ZrO2. The average grain size slightly increased with the increase of ZrO2. The phase transition temperature from tetragonal ferroelectric to cubic paraelectric was about 465 to 466 °C for all sintered samples.
169
Authors: C. Wattanawikkam, Theerachai Bongkarn
Abstract: The effect of firing temperatures on phase formation and microstructure of barium stannate titanate [Ba(Sn0.1Ti0.9)O3; BST10] ceramics were investigated. BST10 was synthesized via a combustion method, at various calcination and sintering temperatures. It was found that, a single perovskite of BST10 powders was obtained with a calcinations temperature of 1200 oC. The percent of the perovskite phase and the lattice parameter were increased with increasing calcination temperatures. The average particle size was increased from 0.48 to 1.69 µm by increasing the calcined temperature from 600 to 1200 oC. The average grain sizes were increased from 0.99 to 17.77 µm by increasing the sintering temperature from 1250 to 1450 oC. The maximum density and dielectric constant were observed in sintered samples at 1350 oC.
173
Authors: Theerachai Bongkarn, R. Sumang
Abstract: In this work, we studied the effect of excess PbO doping on lead barium titanate [(Pb0.925Ba0.075)TiO3; (PBT)] ceramic. PBT was prepared via a mixed oxide method with various PbO levels (-3, 0, 1, 3, 5 and 10 wt.%). The excess PbO was added to compensate the loss from evaporation during calcination and sintering at 800 oC and 1150 oC. It was found that lead barium titanate powders indexed in a tetragonal structure. Impurity phases of lead oxide (PbO), titanium oxide (TiO), and lead dioxide (PbO2) were detected in the calcined powders with higher than 1 wt% of excess PbO. The impurity phase was not obtained in any ceramic samples. The c/a ratios decreased with an increasing excess of PbO in both calcined powders and sintered pellets. The average particle size and the average grain size of the PBT increased with the increase of PbO. The shrinkage plots showed a maximum peak for the 1 wt.% sample which was also the most dense sample.
177
Authors: Theerachai Bongkarn, W. Khiawwangthong
Abstract: In this work, the optimum conditions for the preparation of barium stannate titanate (Ba(Sn0.05Ti0.95)O3 ; BST5) ceramics by solid state reaction method were investigated. The samples were heated at calcination temperatures from 600 to 1200 oC for 4 h and sintering temperatures from 1250 to 1400 oC for 2 h. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were used to evaluate the optimum conditions for calcination. The phase formation was carried out by X-ray diffractometer (XRD). The microstructure was studied by using a scanning electron microscope (SEM). It was found that, a high purity of perovskite powders were obtained with a calcinations temperature at 1200 oC. The percent of the perovskite phase and lattice parameter a were increased by increasing the calcination temperatures. The average particle size was increased from 0.6 to 1.0 µm when increasing the calcination temperatures from 600 to 1200 oC. A pure cubic perovskite phase was found in all the sintered samples. The average grain size is in the range of 1.2 to 43.3 µm when increasing of sintering temperatures from 1250 to 1400 oC. The maximum of density and dielectric constant was observed in a 1400 oC sintered pellet.
181
Authors: Theerachai Bongkarn, C. Wicheanrat
Abstract: This study concentrated on the crystal structure and microstructure of [(Ba0.75Sr0.25)TiO3; (BST)] ceramics at different firing temperatures. The BST powders were prepared by a combustion method. (CO(NH2)2) was used as a fuel. Crystallinity of the calcined powders was improved by increasing the calcining temperature, as indicated by the increase in intensity of the X-ray diffraction peak. The pure perovskite phase of BST powders was obtained with a calcinations condition of 1200 oC. The a axis lattice constant of BST calcined powders and sintered ceramics were calculated and it was found that the crystal structure is a cubic phase. The microstructure of BST calcined powders and sintered ceramics were analyzed by a scanning electron microscope (SEM). The SEM result indicated that the average particle size and average grain size increased with the increase of calcinations and sintering temperatures, respectively. The apparent density of the samples was measured by the Archimedes method.
185
Authors: Y. Suwan, Anuson Niyompan, Rungnapa Tipakontitikul, Pitak Laoratanakul
Abstract: The PZT-PMN ceramics system was derived from Pb(Zr0.5Ti0.5)O3 and Pb(Mg2/3Nb1/3)O3 based compositions those obtained via the columbite method. The effect of MnO2 addition on microstructure, physical properties and piezoelectric properties were investigated. In this study, the composition with PZT/PMN ratio of 1:1 was selected. To observe the effect of MnO2 adding, its concentration was varied in range 0-10 mol%. Green pellets were sintered at temperature 1250oC for 4 hours. For piezoelectric investigation, the ceramics pellets were subjected to a poling process. The XRD results show that there is no phase transformation observed for all sintered PZT-PMN samples with presence of MnO2. The SEM micrographs reveal that MnO2 can enhance sinterability as evidenced by lowering of porosity and increasing of grain size with increasing of MnO2 content. Increasing of linear shrinkage and apparent densities also confirmed such effect. Improvement of d33 from 28 to 114 pC/N could only found for MnO2 in range 0 to 4 mol%. For higher MnO2 content, there is only slightly increased. However, increasing of kp with increasing of MnO2 is clearly observed. While dielectric constant measured at room temperature and at frequency 1 kHz is higher for ceramics without MnO2 doping and it decreases with increasing MnO2 concentration. The temperature dependence of relative dielectric constant go to peak of value about 6000 at temperature around 180oC and shifting of these peaks with frequency can only be observed for samples with higher MnO2 content. This indicates a normal ferroelectric behavior for sample with lower MnO2 and there are converted to relaxor after MnO2 increased.
189
Authors: W. Tangkawsakul, Panadda Sittiketkron, Theerachai Bongkarn
Abstract: In this work, we studied the effect of excess PbO on crystal structure, microstructure and phase transition of lead titanate (PT). PT was prepared via a mixed oxide method with various PbO levels (0, 1, 3 and 5 wt.%). The raw materials were calcined at 750 oC for 2 h and sintered at 1225 oC for 2 h. The characteristics of PT were analyzed by a X-ray diffractometer (XRD), scanning electron microscopy (SEM) and differential scanning calorimeter (DSC). It was found that calcined powders and sintered ceramics indexed in a tetragonal structure. For PT powders, the impurity phases of lead oxide (PbO) and lead dioxide (PbO2) were detected in 3 and 5 wt.% of excess PbO samples, but they were not detected in all sintered ceramic samples. The increase of excess PbO levels resulted in a decreased c/a ratio in both calcined powders and sintered ceramics. Average particle sizes increased from 0.64 to 4.24 µm when excess PbO levels increased from 0 to 5 wt.%. It was also clearly seen that the liquid phase of the sintering process was obtained in the PT calcined powders which had an excess of PbO. The DSC result indicated that the phase transition temperature, from a ferroelectric to a paraelectric phase with a high PbO content (5 wt.%), was higher than those with low PbO contents (0, 1 and 3 wt.%).
193
Authors: Atthakorn Thongtha, Kritsana Angsukased, Theerachai Bongkarn
Abstract: The effect of calcination temperatures (1000-1400 oC) on the phase formation and microstructure of barium strontium zirconate titanate [(Ba0.25Sr0.75)(Zr0.75Ti0.25)O3 ; BSZT] powders were investigated. BSZT powders were prepared and compared by the solid state reaction method and the combustion technique. The higher calcination temperatures increased the percentage of the perovskite phase, but decreased the lattice parameter a. The same crystallographic pure perovskite phase of BSZT powders, which were prepared via the combustion technique were detected above 1300 oC ; which was lower than the calcinations temperature of mixed oxide method by 50 oC. The TGA-DTA results corresponded to XRD investigation. The microstructure of BSZT powders, which were prepared using both techniques, exhibited an almost-spherical morphology and had a porous agglomerated form. The average particle sizes of BSZT powders prepared via the combustion technique (0.13-0.30 µm) and the solid state reaction method (0.18-0.38 µm) were increased with the increase of calcinations temperatures
197
Authors: Theerachai Bongkarn, C. Thiangchit
Abstract: In this study, lead barium zirconate titanate [(Pb0.975Ba0.025)(Zr1-xTix); (PBZT)] powders with 0 £ x £1 were prepared via the mixed oxide method. The calcinations were performed between 800 and 1000 oC for 1 h. The phase formation and microstructure was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the structural phase indexed in the orthorhombic phase for x = 0. The tetragonal phase was detected in 0.25 £ x £ 1 samples. TG and DTA curves corresponded to XRD results. The SEM result indicated that the particle size of the powders were nonconsistant and ranged from ~0.5 to ~1.3 µm.
201

Showing 41 to 50 of 233 Paper Titles