Papers by Author: Supon Ananta

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: 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.

Abstract: The 3 mol% Nb2O5 doped Pb(Zr0.52Ti0.48)O3 with addition of 1-3 mol% Cr2O3 prepared via the solid-state reaction technique have been investigated. The XRD shows that a sample is primarily in both tetragonal and rhombohedral phases coexist and the amount of rhombohedral phase decreases that is due to the donor (Nb) dopant reduces the number of oxygen vacancies and leads to a lower amount of rhombohedral phase. The maximum dielectric constant tend to decrease with increasing Cr doping concentration from 0.1 to 1 mol%. Further increase in Cr concentration, the maximum dielectric constant increase dramatically. The hysteresis loop measurements, the electrical coercivity and the remnant polarization do not show a systematic trend at low concentration of Cr doping. It is possibly due to the partial solubility of Cr doping. The observations clearly indicate the hardening behavior at higher concentration because of more solubility of Cr.

Abstract: Apart from aging effect, barium titanate ceramics usually subjected to the mechanical loading when it is used in electronic device. Thus, it is very interesting to investigate the influence of various compressive stresses on ferroelectric aging behavior of Ba(Ti0.99-xFe0.01Nbx)O3 , x=0.005-0.015. In this study, the P-E hysteresis loops were observed by using compressometer in conjunction with a modified Sawyer-Tower circuit. The stress level was varied from 0 to 185 MPa. The results showed that the dissipation energy, saturation polarization (Psat), remnant polarization (Pr) and the coercive field (Ec) decreased with increasing of stress. The aging behavior was still observed in acceptor-dominant of hybrid doped ceramics. The aging was also enhanced under application of the external stress. The explanation based on the defect-dipole and domain-reorientation processes was discussed.

Abstract: The Bi0.2K0.8(Zn0.1Ti0.1)Ta0.8O3 and Li doped ceramics prepared via the solid-state reaction technique were investigated. The XRD patterns show the single phase cubic perovskite structure without any evidence of secondary phases when sintered at 1250 oC for undoped Bi0.2K0.8(Zn0.1Ti0.1)Ta0.8O3 and sintered at 1100 oC for Li doped one. The dielectric properties indicate the diffused phase transition (DPT). The dielectric loss of undoped ceramic increases with increasing frequency in temperature range 270 oC down to -150 oC, which suggests low temperature relaxation, while the dielectric loss of Li doped ceramic reveals the interesting lower value over a wide temperature range of about 0 - 300 oC.

Abstract: In this study, a room temperature aging behavior of Ba(Ti0.99Fe0.01)O3 was investigated. It was found that the dielectric constant decreased with time and ferroelectric P-E hysteresis loops became constricted loops after aging. Moreover, the room temperature aging behavior under various stresses was also observed. It was found that the relative changes of dielectric constant with time of Ba(Ti0.99Fe0.01)O3 ceramics under stress were lower than those under the stress-free condition. For P-E hysteresis loop measurement, it can be observed that P-E hysteresis loop of Ba(Ti0.99Fe0.01)O3 ceramics became constricted loops and remanant polarizations (Pr), saturated polarizations (Ps) were decreased after aging under all stress levels. These results suggested that the applied stress may partly clamp the domain wall motion, and altered the aging behavior of the ceramics.

Abstract: Lead-free, bismuth sodium titanate-potassium sodium niobate piezoelectric ceramics (Bi1/2Na1/2)TiO3-(K1/2Na1/2)NbO3 have been prepared by a conventional mixed-oxide method via vibro-milling technique. The (K1/2Na1/2)NbO3 (KNN)-based compositions with a morphotropic phase boundary (MPB) have shown greater advantages over another typical lead-free piezoelectric candidate material system, (Bi1/2Na1/2)TiO3 (BNT)-based MPB materials. More importantly, when used this type of material is often subjected to self-induced or external stress. It is, therefore, of interest to investigate influence of stress on properties of the ceramics. In this study, the influences of compressive stress on the dielectric properties of BNT-KNN ceramics were investigated. The dielectric properties were determined under compressive stress applied parallel to electric field. The results indicate significant changes of both properties with the imposed compressive stress. The results were explained in terms of non-180˚ domain switching and de-aging of the dielectric properties under the influence of the applied stress.