Vittayakorn, Wanwilai
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Preferred name
Vittayakorn, Wanwilai
Alternative Name
Vittayakorn, W.
Vittayakorn, Wanwilai C.
Main Affiliation
Email
wanwilai.vi@kmitl.ac.th
41 results
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Item type:Publication, Electrical conductivity, magnetism, and optical properties of reduced BaCeO 3(2019-03-01); ; Kolodiazhnyi, TarasBaCeO <inf>3</inf> -based perovskites are well-known proton and oxygen ion conductors. For practical applications as electrolytes in solid oxide fuel cells, these compounds must be robust towards reduction of cerium ion. In this work, we explore the effect of reducing atmosphere on the physical properties of undoped and Nb-doped BaCeO <inf>3</inf> . The BaCeO <inf>3</inf> perovskite structure is thermodynamically stable at least up to 1450 <sup>∘</sup> C upon annealing in H <inf>2</inf> -containing atmosphere. Annealing at 1550 <sup>∘</sup> C causes a decomposition of the BaCeO <inf>3</inf> . The higher annealing temperature leads to higher concentration of Ce <sup>3 +</sup> ions and a higher electrical conductivity. With increasing the annealing temperature from 1300 to 1450 <sup>∘</sup> C , the activation energy of conductivity decreases from E <inf>a</inf> = 0.31–0.263 eV. We attribute the electrical conductivity in reduced BaCeO <inf>3</inf> to the activation of the small polaron hopping in agreement with the recent first-principles calculations. However, in contrast to the theoretical predictions, we find no evidence of the Ce <sup>3 +</sup> –Ce <sup>3 +</sup> spin-singlet small bipolarons. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Electrical and dielectric properties of barium titanate–polydimethylsiloxane nanocomposite with 0-3 connectivity modified with carbon nanotube (CNT)(2019-01-02); This study explored the preparation and electrical properties of 0–3 barium titanate/polydimethylsiloxane nanocomposites by dispersing barium titanate nanoparticles (BaTiO<inf>3</inf>; BT) into the polydimethylsiloxane (PDMS) matrix phase. The effect of barium titanate nanoparticles on electrical properties has been investigated systematically, and the relative permittivity of nanocomposites was found to increase significantly with increasing barium titanate content. Different theoretical models were used to predict the dielectric constant of these composites and compare their experimental value with the theoretical value in order to find an appropriate equation. The result indicated that the dielectric properties of composites are influenced not only by relative permittivity of the components but also dependence on interactions between ceramics and polymers. Furthermore, the preparation and dielectric properties of BT/PDMS nanocomposites modified with carbon nanotube (CNT) were also studied. The dielectric results demonstrate that adding CNT can enhance the relative permittivity of the BT/PDMS composite via improvement of dispersion and distribution of the BT nanoparticles in the PDMS matrix phase. Moreover, the electrical outputs from the BT/PDMS/CNT nanocomposites generator were measured under periodic knocking. The nanocomposites innovatively expand the feasibility of self-powered energy systems for smart sensor and energy harvesting applications. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Utilization of eggshell as a low-cost precursor for synthesizing calcium niobate ceramic(2018-07-18); ; - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Magnetoelectric properties of BaTiO3 - Co0.5Ni0.5Fe2o4 composites prepared by the conventional mixed oxide method(2013-10-29); Multiferroics, which display simultaneous ferrimagnetic and ferroelectric properties, have been interesting recently because of their potentially significant applications in multifunctional devices such as magnetic resonance, drug delivery, high-density data storage, ferrofluid technology, etc. Composites combining BaTiO<inf>3</inf> with Co<inf>0.5</inf>Ni<inf>0.5</inf>Fe<inf>2</inf>O<inf>4</inf> have influenced the interest of many researchers, due to their outstanding and distinguished character called magnetoelectric (ME). In this work, ferrimagnetic-ferroelectric composites of BaTiO<inf>3</inf> nanopowder and Co<inf>0.5</inf>Ni<inf>0.5</inf>Fe<inf>2</inf>O<inf>4</inf> nanopowders were prepared by a conventional mixed oxide method. The multiferroic ceramics were compounded with the formula, (1-x)BaTiO<inf>3-</inf>(x) Co<inf>0.5</inf>Ni<inf>0.5</inf>Fe<inf>2</inf>O<inf>4</inf>, in which x = 0, 0.05, 0.10, 0.20 and 0.35. All of the compositions were analyzed by an X-ray diffractometer (XRD) in order to reveal the phase of perovskite and spinal structure. Scanning electron microscopy (SEM) was used to examine the variation of morphology and grain size of the composited ceramics. The magnetism of all the ceramics was measured using a vibrating sample magnetometer (VSM). The results showed that microstructure and the amount of ferrite are related strongly with magnetization. © (2013) Trans Tech Publications, Switzerland. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Direct synthesis and growth mechanism of metal molybdate (AMoO4; A = Ca and Ba) fine particles via the mechanochemical method(2017-08-01); Metal molybdate (AMoO<inf>4</inf>; Ca and Ba) fine particles were synthesized successfully in a simple way using the mechanochemical method under ambient conditions, without surfactants or any capping agents. The effect of milling time on phase formation and morphology was investigated. The functional group and phase formation analyses were carried out using Fourier transform infrared (FT-IR), Raman spectroscopy and X-ray diffraction (XRD) methods. XRD revealed that all samples were of a pure tetragonal scheelite structure. FT-IR and Raman analysis exhibited a Mo-O stretching peak of molecular [MoO<inf>4</inf>]<sup>2-</sup>, which related to the scheelite structure. Difference in growth mechanism and morphology was observed significantly in CaMoO<inf>4</inf> and BaMoO<inf>4</inf> particles. The primary CaMoO<inf>4</inf> nanocrystalline was formed in its initial state at 80–100 nm, and tended to aggregate into a peach-like shaped morphology with increasing milling time, while a space shuttle-like morphology formed directly via an oriented attachment mechanism for the BaMoO<inf>4</inf> particle. A possible mechanism for the formation of metal molybdate, with a different milling time, was discussed in detail. It is interesting that this work was able to present a simple way of synthesizing complex oxide materials on a large scale. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Effect of Sn content on the dielectric and piezoelectric properties of the ternary system (0.975-y)BaTiO3–0.025SrTiO3–yBaSnO3(2017-06-01); ; - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Sonochemical synthesis of monodispersed perovskite barium zirconate (BaZrO3) by using an ethanol-water mixed solvent(2015-07-01); ; ; Maensiri, SantiPerovskite barium zirconate (BaZrO<inf>3</inf>) was synthesized successfully in an ethanol-water mixed solvent under ultrasonic irradiation. Four compositions, including 0%, 30%, 50%, and 70% by volume of ethanol in ethanol/water mixed solvent, were used. The effect of ethanol content and irradiation time on the phase formation and morphology of product particles was studied and discussed. As a result, a pure perovskite BaZrO<inf>3</inf> phase was formed completely at a short irradiation time of about 15 min in 70% by volume of ethanol without the calcination process. The average particles size decreases and particle size distribution becomes narrower by increasing the percentage of ethanol volume. On the other hand, the monodispersibility of BaZrO<inf>3</inf> particles was improved significantly through ultrasonic irradiation. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Fine Grain BaTiO3-Co0.5Ni0.5Fe2O4 Ceramics Prepared by the Two-Stage Sintering Technique(2015-10-30); ; This work investigated the improvement of density and controllable grain size of multiferroic ceramics by using the system of (0.8)BaTiO<inf>3</inf>-(0.2)Co<inf>0.5</inf>Ni<inf>0.5</inf>Fe<inf>2</inf>O<inf>4</inf> nanocomposites via the two-stage sintering technique. The sintering process was divided into two steps. Firstly, samples were fired at the optimized temperature of T<inf>1</inf> to activate grain boundary migration in order to obtain an initial high density. Secondly, the samples were cooled immediately to the temperature of T<inf>2</inf> and soaked at various times to enable dense ceramics without grain growth. All of the samples were characterized by an X-ray diffractometer, and the results confirmed that all samples were composite ceramics. Scanning electron microscopy showed the grain size of all the samples and proved that the two-stage sintering technique achieved fine grain ceramics when compared with traditional sintering. Electrical properties of all the samples were investigated using an LCR meter at room temperature to 200°C with various frequencies, and magnetic properties were characterized by a vibrating sample magnetometer. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Giant suppression of dielectric loss in BaZrO3(2019-11-01); We report the effect of precursor's purity and heterovalent substitution on the microstructure and dielectric properties of BaZrO<inf>3</inf> ceramics. We find that independent of the purity or raw materials, the dielectric loss of BaZrO<inf>3</inf> at microwave frequencies is rather high with a Q factor in the range of 1000–3000 at 10 GHz. All stoichiometric ceramics studied show up to three types of low-T dielectric relaxations in the 2–250 K range. All these dielectric anomalies can be suppressed by partial substitution of Zr for Nb. By alloying of BaZrO<inf>3</inf> with a hypothetical BaGa<inf>1/2</inf>Nb<inf>1/2</inf>O<inf>3</inf> phase the Q × f value of ceramics at microwave frequency can be improved significantly. The origin of this remarkable improvement is attributed to the effect of the donor ions on the random electric fields and antiferrodistortive instability. Ceramic with a chemical composition of BaZr<inf>0.96</inf>Ga<inf>0.02</inf>Nb<inf>0.02</inf>O<inf>3</inf> sintered at 1600 °C shows dielectric constant, ε′ = 36.7, temperature coefficient of the resonance frequency, τ<inf>f</inf> = +110 ppm/°C and Q × f = 172 THz. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, High piezoelectric response in lead free 0.9BaTiO3-(0.1-x)CaTiO3-xBaSnO3 solid solution(2017-08-01); ;