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The disordered cation distribution studies of nanosized zinc ferrite powders by synchrotron X-ray absorption spectroscopy
(2016-04-26)
Tangcharoen, Thanit
;
Klysubun, Wantana
;
Kongmark, Chanapa
;
Pecharapa, Wisanu
The non-equilibrium site occupancy of zinc (Zn2+) and ferric (Fe3+) ions in dissimilar nanosized zinc ferrites (ZnFe2O4)powders obtained from the different milling time (0 to 24 h) of the as-combusted powders was investigated through Zn and Fe K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra. Compared with the bulk specimen of zinc ferrite, both XANES and EXAFS spectra of nanosized zinc ferrite powders clearly exhibit the large Zn2+ ions translocation from the tetrahedral (A) sites to the octahedral (B) sites leading to the movement of many Fe3+ ions in the opposite direction without the variation in the long-range structural order.
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Effect of Zn:Sn ratio and calcination temperature on phase transformation of Zn-Sn-O compound
(2016-01-01)
Nakhanivej, Puritut
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Tangcharoen, Thanit
;
Mekprasart, Wanichaya
;
Pecharapa, Wisanu
Zn-Sn-O powders were synthesized by simple co-precipitation method combined with calcination process using zinc chloride (ZnCl<inf>2</inf>) and tin (IV) chloride pentrahydrate (SnCl<inf>4</inf>·5H<inf>2</inf>O) as starting precursors of Zn and Sn in aqueous solution. The effect of precursors ratio on phase structure of Zn-Sn-O compound was investigated by varying ratio of Zn:Sn in the co-precipitation system. For the effect of calcination temperature, the as-precipitated product obtained at Zn: Sn ratio of 1:1 was calcined at different temperatures (400-900°C) to study phase transformation. Structural properties of as-precipitated and after-calcined powders were characterized by X-ray diffraction (XRD) while surface morphologies of final products were observed by scanning electron microscope (SEM), and thermogravimetric analysis (TGA) was used to study their thermal properties. The results indicate that the XRD pattern of Zn-Sn-O powders obtained at ratio of Zn greater than Sn can be assigned to mixed phase of ZnO and Zn<inf>2</inf>SnO<inf>4</inf>. On the other hand the XRD patterns of products obtained at ratio of Sn greater than Zn confirm a mixture of SnO<inf>2</inf> and Zn<inf>2</inf>SnO<inf>4</inf>. For the effect of calcination temperature, the rarely spinel phase of Zn<inf>2</inf>SnO<inf>4</inf> begin occur with mixed phase of ZnO and SnO<inf>2</inf> at the calcination temperature of 600°C and pure spinel structure can be obtained at the temperature above 900°C.
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Effect of Zn:Al ratio and calcination time on structural properties of Zn-Al-O compound
(2016-01-01)
Mekprasart, Wanichaya
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Worasawat, Suchada
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Tangcharoen, Thanit
;
Pecharapa, Wisanu
Zn-Al-O compounds were successfully synthesized via co-precipitation method at pH 8 followed by calcination process at 900 °C. Influence of different precursor (Zn:Al) ratio and calcination time on their structural properties and formation have been investigated. Varying Zn:Al ratio was conducted at 2:1, 1:1, 1:2 and 1:4 with different calcination time at 0, 2, 4, and 6 h. Phase transformation and morphologies were characterized by X-ray diffraction and field-emission scanning electron microscope. Moreover, chemical bonding of Zn-Al-O compound was analyzed by Raman spectroscopy. The results indicated that chemical bonding between Zn-Al oxide evidentially occurred in all samples in composite form and spinel structure. In addition, the amount of Al content considerably contributes to significant aggregation in zinc aluminate (ZnAl<inf>2</inf>O<inf>4</inf>) spinel crystalline phase affirmed by XRD result. Meanwhile, SEM images reveal high crystallinity and strong formation of the compound obtained by prolong calcined period.
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Synthesis and characterization of cubic-like zinc stannate powders prepared by co-precipitation method
(2016-01-01)
Mekprasart, Wanichaya
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Tangcharoen, Thanit
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Nakhanivej, Puritat
;
Pecharapa, Wisanu
Spinel-type zinc stannate (Zn<inf>2</inf>SnO<inf>4</inf>) powders were synthesized by co-precipitation method using zinc chloride and tin chloride as the precursors for Zn and Sn sources, respectively. Co-precipitation process is one of effective techniques due to non-complex system, short process time, high yield, large scale production and cost-effectiveness comparing to other methods. The influence of calcination temperature in the range of 900 °C to 1100 °C on the structure, morphologies and cation distribution were studied using various characterization techniques. A single spinel structure phase formation after-calcined powders are confirmed by X-ray diffraction (XRD) results meanwhile scanning electron microscope (SEM) showed the appearance of cubic-like shape. The aggregation of particle and strong crystallinity was distinctly increased resulting to their greater size by the effect of high calcined temperature. Moreover, the non-equilibrium site occupancy of zinc (Zn2+) and tin (Sn4+) ions was investigated through Zn K-edge and Sn L3-edge investigated by X-ray absorption (XAS) spectra via the synchrotron radiation light source. Compared with the calcined temperature sample, XANES spectra revealed that the oxidation state of Zn was +2 and Sn valence was +4 in all spinel Zn<inf>2</inf>SnO<inf>4</inf> samples which well corresponds to the theoretical values.
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Synchrotron X-ray absorption spectroscopy study of disordered cation distribution of nanosized zinc ferrite powders
(2016-01-01)
Tangcharoen, Thanit
;
Kongmark, Chanapa
;
Klysubun, Wantana
;
Pecharapa, Wisanu
The zinc ferrite (ZnFe<inf>2</inf>O<inf>4</inf>) powders of various nanoparticle sizes were synthesised at different milling times (0 to 24 h) of the as-combusted powders. The non-equilibrium site occupancy of zinc (Zn2+) and ferric (Fe3+) ions was investigated through Zn and Fe K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra. The XRD and SEM strongly confirm the particle size of these ferrites decreasing with the increasing milling time. Compared with the bulk specimen of zinc ferrite, both XANES and EXAFS spectra of zinc ferrite powders clearly exhibit the large translocation of Zn2+ ions from the tetrahedral (A) sites to the octahedral (B) sites and the opposite translocation of some of Fe3+ ions without affecting the long-range structural order. Moreover, the curve-fitting analysis of Zn and Fe K-edge EXAFS spectra indicates that the degree of inversion increases as the particle size decreases resulting in significant differences in the magnetic behaviours.
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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
;
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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Effect of Precursor Concentration on Physical Properties of Cube-Like Zn2SnO4 Powders Synthesized by Co-Precipitation Method
(2015-09-02)
Mekprasart, Wanichaya
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Nakhanivej, Puritat
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Tangcharoen, Thanit
;
Pecharapa, Wisanu
Cube-like Zinc stannate (Zn<inf>2</inf>SnO<inf>4</inf>) spinel powders were synthesized by co-precipitation method using chloride starting precursors of zinc and tin. The influence concentration of precursors on relevant physical properties of Zn<inf>2</inf>SnO<inf>4</inf> was investigated by increasing concentration of precursor material at 0.1 to 0.4 M (Zn:Sn at ratio 1:1). Structural properties of as-synthesized and Zn<inf>2</inf>SnO<inf>4</inf> crystal were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray absorption spectroscopy (XAS). The results indicate that as-prepared material without calcination process is in cubic symmetry of zinc hydroxy stannate (ZnSn(OH)6) affirmed by SEM and XRD results. Meanwhile, spinel phase of Zn<inf>2</inf>SnO<inf>4</inf> with strong crystalline and eminent cubic structure can be achieved after calcination at 1000°C. Homogenous dispersion, high crystallinity and good cubic structure of Zn<inf>2</inf>SnO<inf>4</inf> powders are occurred at higher concentration of precursors. Moreover, the oxidation state of these samples were investigated by the Zn K-edge and Sn L3-edge X-ray absorption near edge structure (XANES) using the synchrotron radiation light source. The analyses of XANES spectra revealed that the oxidation state of Zn was +2 and Sn valence was +4 in all Zn<inf>2</inf>SnO<inf>4</inf> samples, which well corresponds to the theoretical values. © 2015
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Characterization and effect of calcination temperature on structural properties of spinel zinc aluminate synthesized via Co-precipitation process
(2015-06-01)
Mekprasart, Wanichaya
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Worasawat, Suchada
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Tangcharoen, Thanit
;
Pecharapa, Wisanu
Zinc aluminate (ZnAl<inf>2</inf>O<inf>4</inf>) nanopowders were synthesized by co-precipitation method using zinc chloride and aluminum chloride as starting precursors. The calcination temperature which was a crucial preparation factor was varied and its influence on relevant physical properties of the product was investigated. Structural properties of synthesized nanoparticles were investigated by X-ray diffraction, X-ray absorption spectroscopy, scanning electron microscope, and Raman spectroscopy. The results suggest that that ZnAl<inf>2</inf>O<inf>4</inf> in spinel structure with high crystallinity can be obtained after calcination beyond specific temperature affirmed by XRD results. Raman result indicates the correlated chemical bonding relating to the formation of ZnAl<inf>2</inf>O<inf>4</inf> structure. Meanwhile, the Zn K-edge X-ray absorption near-edge structure (XANES) spectra of these samples with different calcination temperature obtained from the synchrotron X-ray absorption spectroscopy measurement show the existence of accurate oxidation state for zinc ion (Zn2+) in the spinel crystal structure. Moreover, it is revealed that the calcination temperature has significant effect on the local environment of the zinc absorbing atoms through the interesting change of white line appearance.
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A comparison of cation distribution and valence state in spinel crystal structure of zinc and nickel ferrites using the synchrotron X-ray absorption spectroscopy (XAS) analysis
(2014-07-24)
Tangcharoen, Thanit
;
Klysubun, Wantana
;
Ruangphanit, Anucha
;
Pecharapa, Wisanu
In this work, the physical structure, magnetism and local structure of zinc and nickel ferrites (ZnFe<inf>2</inf>O<inf>4</inf> and NiFe<inf>2</inf>O <inf>4</inf>) synthesized by typical sol-gel combustion method, were investigated by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The formation of the single phase cubic spinel crystal structure and the different values of crystallite size (D), interplanar distance (d) and lattice constant (a) for all ferrite samples were evaluated by the XRD data. The VSM measurement provides the characteristic magnetic hysteresis loop (M-H) for each sample which was found to be significantly different from each other. The chemical shifts in Zn, Ni and Fe K-edges XANES spectra indicate the existence of Zn2+, Ni2+ and Fe3+ ions in these ferrites. The EXAFS spectra analyses applied to track Zn, Ni and Fe cation distribution indicate the distinct character of spinel crystal structure of both ferrites. The results exhibit that zinc ferrite is a normal spinel, while the nickel ferrite is an inverse spinel. Moreover, these EXAFS spectra analyses reveal that the distances between metal ion (Zn2+ or Ni2+) to central oxygen ion and to Fe3+ ions in the opposite lattice site for each ferrite sample are unequal which highly affect its magnetism. The overall simulated results are one of the important evidence encouraging the explanation on the paramagnetism for ZnFe<inf>2</inf>O<inf>4</inf> and the ferrimagnetism for NiFe<inf>2</inf>O<inf>4</inf>. © 2014 Taylor & Francis Group, LLC.
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Synchrotron X-ray absorption spectroscopy and magnetic characteristics studies of metal ferrites (metal = Ni, Mn, Cu) synthesized by sol-gel auto-combustion method
(2014-01-01)
Tangcharoen, Thanit
;
Klysubun, Wantana
;
Kongmark, Chanapa
;
Pecharapa, Wisanu
In this work, the metal ferrites MFe<inf>2</inf>O<inf>4</inf> (M = Ni, Mn, Cu) were synthesized from metal nitrate precursors by the sol-gel auto-combustion method using diethanolamine (DEA) as a potential fuel. The crystal structures of these ferrite powders were characterized by X-ray diffraction (XRD) technique confirming the complete formation of the single-phase cubic spinel crystal structure. The ferrimagnetism characteristic and the difference of the magnetic properties such as saturation magnetization (M<inf>s</inf>), remanent magnetization (M<inf>r</inf>), and coercivity (H <inf>c</inf>) for each after-calcined ferrite sample were scrutinized through the ferrimagnetic hysteresis loop (M-H) obtained from the vibrating sample magnetometer (VSM) measurement. Moreover, the cation distribution and valence state of these ferrites were investigated by the Ni, Mn, Cu, and Fe K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra using the synchrotron radiation light source. From the XAS results, the analyses of both XANES and EXAFS spectra show the existence of accurate oxidation state for transition metal ions and the interionic distance to the nearest neighbors in the spinel crystal structure. In particular, the curve-fitting analysis of Ni, Mn, Cu, and Fe K-edge EXAFS spectra indicates that the degree of inversion in these metal ferrites is entirely different and found to be 0.2 for MnFe<inf>2</inf>O<inf>4</inf>, 0.8 for CuFe<inf>2</inf>O <inf>4</inf>, and 1.0 for NiFe<inf>2</inf>O<inf>4</inf>, which are the important information for understanding their effects on relevant magnetic properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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