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Efficient and novel synthesis of Nb-doped SrTiO3 nanoparticles via microwave-assisted sol-gel auto-combustion
(2025-02-01)
Nunocha, Pornnipa
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Bongkarn, Theerachai
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Eiad-ua, Apiluck
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Channei, Duangdao
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Suriwong, Tawat
This study employed microwave-assisted sol-gel auto-combustion to synthesize niobium-doped strontium titanate (SrTi<inf>1-x</inf>Nb<inf>x</inf>O<inf>3</inf>, STNO) nanoparticles, targeting enhanced photocatalytic performance applications. The STNO with varying levels of Nb doping (x = 0 to 0.05), was successfully synthesized utilizing the rapid and novel microwave-assisted sol-gel auto-combustion technique. The synthesized nanoparticles consistently exhibited a pure cubic perovskite structure across all doping levels, as confirmed by Rietveld refinement, which also showed an increase in lattice parameters and unit cell volume with higher Nb content. Morphological analysis revealed uniformly cubic-shaped particles with sizes ranging from 60 to 180 nm. The bandgap energy (E<inf>g</inf>) remained unaffected by the varying Nb doping levels. Regarding photocatalytic activity for the degradation of methylene blue (MB) dye and tetracycline (TC) antibiotic under UV-A LED irradiation, the photocatalytic performance of STNO was significantly enhanced with increasing Nb content. The optimal photocatalytic decolorization was achieved at x = 0.05, aligning well with findings derived from photoluminescence (PL), E<inf>g</inf>, Nyquist plot analyses and band edge potentials. Therefore, microwave-assisted sol-gel auto combustion is one of the efficient and novel methods to synthesize metal oxide materials.
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INFLUENCE OF Pr6O11-DOPING ON THE CRYSTAL STRUCTURE AND ELECTRICAL PROPERTIES OF BNBT PIEZOELECTRIC CERAMICS
(2025-01-01)
Yotthuan, Surirat
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Sawangboon, Nuttawan
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Meechoowas, Ekarat
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Bongkarn, Theerachai
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Vittayakorn, Naratip
In this work, a series of lead-free 0.97(Bi<inf>0.5</inf>Na<inf>0.5</inf>)TiO<inf>3-</inf>0.03BaTiO<inf>3-x</inf>Pr<inf>6</inf>O<inf>11</inf> (BNBT-xPr) piezoelectric materials with x=0, 0.1, 0.3, 0.5, and 0.7 wt.% were created by the solid-state combustion route, to enhance their electric properties. The investigation on the phase evolution, microstructure, and electrical behavior of the specimens were carried out. The powders and ceramics were calcined and sintered for two hours at 800℃ and 1180℃, correspondingly. All examples displayed a perfect perovskite lattice and no detectable impurity phase. XRD pattern examination for the ceramics disclosed the existence of rhombohedral and tetragonal phases in all examples. The rhombohedral phase was boosted by rising the doping levels, as established by the Rietveld refinement study. As the x content rose, the average grain size and measured density began to decrease from 0.90±0.10 to 0.73±0.07 μm and 6.13 to 6.05 g/cm3, correspondingly. It was noticed that Pr<inf>6</inf>O<inf>11</inf> doping, decreased dielectric properties. The remnant polarization (Pr) of the samples rises from 22.2 to 27.7 μC/cm2 with x rises from 0 to 0.3 and then dropped. The coercive field (Ec) of the ceramics rises significantly when Pr<inf>6</inf>O<inf>11</inf> was incorporated. The BNBT lead-free ceramics doped with 0.3wt%Pr<inf>6</inf>O<inf>11</inf>, with a high Pr value, could be a promising candidate for memory applications to replace Pb-based ceramics.
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Effecting on electrical performance of Methylammonium Lead Chloride Iodide perovskite films composited by reduced graphene oxide for controlling double Schottky barrier
(2024-06-01)
Butsriruk, Kwanruthai
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Sriwong, Chaval
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Ruttanapan, Chesta
Semiconducting perovskite thin films are cheap to fabricate and can be coated on fluorine-doped tin oxide (FTO) substrates by using simple techniques such as the solution deposition method. In this work, we show that the improved electrical performance of perovskite film produces that of single crystals in an ambient atmosphere. Herein, Methylammonium Lead Chloride Iodide (MAIPbCl<inf>2</inf>) is played as perovskite films, which were composited with different weight percent (wt%) of rGO from 7 to 10. All samples in this work were presented with physicochemical, electrical, and optical properties. However, the challenge of this work is the electron scattering at the grain boundaries as a result of the double schottky barrier. The best decreasing the double schottky barrier yielded a maximum conductivity of 68.72 ± 0.95 S/cm, a low sheet resistance of 5.47 ± 1.64 Ω, a decrease in the lowest oxygen vacancy, and an increase in the grain size from 27.89 nm (of MAIPbCl<inf>2</inf>) to 34.96 nm at room temperature for the MAPbCl<inf>3</inf>-8 wt% rGO composite, which also revealed that this strategy significantly helped to improve the performance of the film. Furthermore, temperature dependence for MAIPbCl<inf>2</inf>-rGO composites demonstrates this high electrical conductivity from room temperature to 323 K, with highest electrical conductivities of 78.68 ± 0.01 S/cm and the activation energy of 0.18 eV at 313 K for 8 wt% rGO. Therefore, MAIPbCl<inf>2</inf>-rGO composite films demonstrated the enhancement of performance of MAIPbCl<inf>2</inf> films; this is next promising for perovskite films in the future.
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A novel fabrication of organic-inorganic hybridized Graphene-La2CrFeW6 nanocomposite and its improved photovoltaic performance in DSSCs
(2021-06-01)
Oh, Won Chun
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Liu, Yin
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Areerob, Yonrapach
We fabricated a novel nanocomposite composed of graphene-La<inf>2</inf>CrFeW<inf>6</inf> perovskite compounds with an organic-inorganic counter electrode based on CdSe, gallic acid, urea and sulfate in dye-sensitized solar cells (DSSCs) by a simple hydrothermal technique. The nanocomposite shows an excellent electro–catalytic activity with low charge-transfer resistance, due to the synergetic catalytic effects of the graphene sheets and La<inf>2</inf>CrFeW<inf>6</inf> perovskite with organic-inorganic materials. The special structure of this nanocomposite also improves the active sites for reduction of triiodide ions on the counter electrodes. The photo-conversion efficiency of the DSSC fabricated using a gallic-based counter electrode reached a higher value of 10.40% under standard illumination (1 sun, 100 mW cm−2, AM 1.5), as compared to the traditional Pt electrode (7.49%). The graphene-La<inf>2</inf>CrFeW<inf>6</inf> fabricated with an organic-inorganic based CE was also found to be more efficient than those reported in previous works, in which graphene, produced by various methods, was used as a CE material. Therefore, the present nanocomposite is considered an environmentally friendly, low-cost, and highly efficient CE material for DSSCs.
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Ba0·5Sr0·5(Co0·8Fe0.2)1-xTaxO3-δ perovskite anode in solid oxide electrolysis cell for hydrogen production from high-temperature steam electrolysis
(2021-02-08)
Prasopchokkul, P.
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Seeharaj, P.
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Kim-Lohsoontorn, P.
Among perovskite anodes in solid oxide electrolysis cell (SOEC), Ba<inf>0·5</inf>Sr<inf>0·5</inf>Co<inf>0·8</inf>Fe<inf>0·2</inf>O<inf>3-δ</inf> (BSCF) has gained much attention due to its dominantly high performance. However, the BSCF still suffers from chemical instability. In this study, the B-site of BSCF is partially substituted by a higher valence Ta5+ (5, 10, 15 and 20 mol%) to improve its structural stability - Ba<inf>0·5</inf>Sr<inf>0·5</inf>(Co<inf>0·8</inf>Fe<inf>0.2</inf>)<inf>1-x</inf>Ta<inf>x</inf>O<inf>3-δ</inf> (BSCFTax, 0 ≤ x ≤ 0.20). It is found that doping with higher valence Ta5+ increases both chemical stability and electrochemical performance of BSCF. Although the BSCFTa0.10 shows the lowest oxygen vacancies indicating by the ratio of adsorbed oxygen vacancies (O<inf>adsorbed</inf>) to lattice oxygen (O<inf>lattice</inf>), the electrochemical performance increases. The decrease in Co3+/Co4+ ratio results in increasing electronic conductivity in the anode. It is likely that proper amount of Ta5+ doping provide a balance between ionic and electronic conductivity in the anode and improved electrochemical performance. The symmetrical half-cells with electrolyte support (BSCFTa/YSZ/BSCFTa) are fabricated to determine the area specific resistance (ASR) and activation energy of conduction - BSCFTa0.10 shows the best performance. Cathode-supported Ni-YSZ/YSZ/BSCFTa0.10 also shows higher durability than Ni-YSZ/YSZ/BSCF (operating at current density −0.45 A cm−2 in electrolysis mode, 80 h, 800 °C and H<inf>2</inf>O to H<inf>2</inf> ratio of 70:30).
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Sonochemical Synthesis, Characterization, and Photocatalytic Activity of Perovskite ZnTiO3 Nanopowders
(2016-10-01)
Wattanawikkam, Chakkaphan
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Pecharapa, Wisanu
Perovskite zinc titanate (ZnTiO<inf>3</inf>) nanopowders were synthesized using the sonochemical method combined with calcinations at 500 °C and 900 °C for 2 h to improve their crystallinity. The effect of calcination temperature on their structural, optical, and photocatalytic properties has been studied. The cubic phase and the mixing phase of cubic and hexagonal were observed in sample calcined at 600 °C and 700 °C, respectively, while the spinel ZnTiO<inf>3</inf> and rutile TiO<inf>2</inf> phase arises in sample calcined over 700 °C. The valence state was investigated by the X-ray absorption near-edge spectroscopy technique, and the corresponding results indicate the existence of Zn2+ and Ti4+ in the powders. The chemical states of the samples were scrutinized by X-ray photoelectron spectroscopy. The average particle size is approximately 20-240 nm. The excellent photocatalytic performance of ZnTiO<inf>3</inf> nanoparticle calcined at 700 °C gave complete degradation Rhodamine B (RhB) in 75 min under ultraviolet light exposure with the k rate of 0.033 min-1 and 55% of decolorization RhB in 210 min under visible irradiation. The sample calcined at 700 °C ensures a good dielectric permittivity with a value 20 and the loss tangent of about 10-2.
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First Principles Calculations of Structural and Elastic Properties of Perovskite Crystals: The Case of SrTiO3
(2016-06-01)
Pandech, Narasak
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Sarasamak, Kanoknan
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Limpijumnong, Sukit
The structural and elastic properties of perovskite crystals can be independently calculated by using first principles calculations without bias. The detailed calculation of cubic perovskite (Pm3m) crystal by first-principles calculations both LDA and GGA approaches was shown, using SrTiO<inf>3</inf> as an illustration case. The equilibrium volumes and bulk modulus of SrTiO<inf>3</inf> were evaluated by fitting to Birch-Murnaghan equation of states. The C<inf>11</inf>, C<inf>12</inf>, and C<inf>44</inf> elastic constants were obtained from a polynomial fit to the calculated energy-strain relations. For SrTiO<inf>3</inf>, the calculated lattice constants, bulk modulus, and all three elastic constants by both LDA and GGA calculations are in good agreement with experimental values. Because LDA gives a slightly smaller lattice constant compared to that obtained from GGA, the bulk modulus and all three elastic constants obtained from LDA are slightly larger than those values obtained from GGA. The calculation steps illustrated here can be used as a guideline to study elastic properties of other novel materials.
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High strain response of the (1-x)(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-x BaSnO3 lead free piezoelectric ceramics system
(2016-01-02)
Janbua, Jira
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Niemchareon, Surasak
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Muanghlua, Rangson
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Vittayakorn, Naratip
The system of lead free piezoelectric ceramics, (1-x)(0.94Bi<inf>0.5</inf>Na<inf>0.5</inf>TiO<inf>3</inf>-0.06BaTiO<inf>3</inf>)-xBaSnO<inf>3</inf> [abbreviated as BNT-BT-xBSn] with the compositions, x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.10 was synthesized via the conventional solid state reaction method. All the products from X-ray diffraction patterns showed diffraction peaks as a phase perovskite structure, with no secondary phases. Due to the composition-dependence of the ferroelectric, bipolar and unipolar strain properties were investigated in order to achieve a good new lead free piezoelectric ceramics system. It was noticeable that a large strain of around 0.4%, with a normalized strain value (d<inf>33</inf>∗) of 669 pm/V at the x = 0.02composition, by applying an electric field of 60 kV/cm at room temperature. The results of this study showed that a new BNT-BT-xBSn ceramics system is a very promising candidate for creating a significantly large strain response, which is sufficiently effective for actuator material applications.
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Synchrotron X-ray absorption spectroscopy study of the local atomic structures and cation ordering in perovskite- and spinel-type zinc stannate synthesized by co-precipitation method
(2015-12-15)
Tangcharoen, Thanit
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Kongmark, Chanapa
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Pecharapa, Wisanu
Zinc stannate nanocrystalline powders with two different crystal structures were synthesized from two different initial Zn2+/Sn4+ ratios by a simple co-precipitation method. X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) techniques were used to investigate crystal structure, oxidation, and cation ordering of the after-calcined powders. XRD patterns clearly showed that the ZnSnO<inf>3</inf> perovskite phase was obtained using an equal initial Zn2+/Sn4+ ratio of 1:1, while a double Zn2+ excess sample (2:1) produced the pure Zn<inf>2</inf>SnO<inf>4</inf> spinel phase. The chemical shifts in Zn K- and Sn L3-edge XANES spectra supported that only Zn2+ and Sn4+ ions existed in these stannate samples. Moreover, the theoretical simulation of the Zn K-edge EXAFS experimental data also indicated a change in the cation ordering from orthorhombic, for perovskite ZnSnO<inf>3</inf>, to cubic for spinel Zn<inf>2</inf>SnO<inf>4</inf>. This is the first time that the local atomic structural characterization of zinc stannate powders derived from EXAFS analysis has been presented.
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Perovskite phase formation, phase transformations and electrical properties of lead-nickel niobate - Lead zirconate ceramics
(2007-12-01)
Vittayakorn, Naratip
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Wirunchit, Supamas
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Trisak, Sakda
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Muanghlua, Rangsan
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Niemcharoem, Susasak
The perovskite structure of lead zirconatelead nickel niobate ceramics, (1-x)PbZrO3-xPb(Ni1/3Nb2/3)O3 (PZ - PNN) with x = 0.0-0.5, were synthesized via the columbite precursor method. The formation of the perovskite phase in the calcined powders has been investigated as a function of calcination conditions by TG-DTA and XRD techniques. The complete solid solutions of perovskite phase of PZ-PNN ceramics were obtained over a wide compositional range. The results showed that the concentration of the PNN phase increased the calcination temperature must be increased in order to obtain phase-pure perovskite. In addition, x-ray diffraction indicated a phase transformation from a orthorhombic to a pseudo-cubic phase when the fraction of PNN was increased. A higher relative permittivity value, as a consequence of the higher PNN concentration, was observed.

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