Rattanai Baitahe

Directed synthesis, growth process and optical properties of monodispersed CaWO4 microspheres via a sonochemical route

Monodispersed calcium tungstate (CaWO4) microspheres were synthesized successfully via a sonochemical process in deionized (DI) water. The functional group and phase formation analyses were carried out using Fourier transform infrared (FT-IR) and X-ray diffraction (XRD), respectively. XRD revealed that all samples were of pure tetragonal scheelite structure. FT-IR and Raman analysis exhibited a W–O stretching peak of molecular [WO4]2−, which related to the scheelite structure. The effect of ultrasonic irradiation times in the sonochemical process was investigated briefly for 1, 5, 15 and 30 min. The shape of the particles was revealed as spherically monodispersed with narrow size distribution and uniform features at the ultrasonic time of 5 min. This study also found that the spherical surface was composed of tightly packed nanosphere subunits. A possible mechanism for the formation of CaWO4 powders with a different ultrasonic time was discussed in detail. Optical properties showed blue light emission at a wavelength of around 420 nm and an optical energy gap (Eg) value of 3.32–3.36 eV.

Synthesis of Monodispersed Perovskite Barium Zirconate (BaZrO3) by the Sonochemical Method

Barium zirconate (BaZrO3) was synthesized successfully by the sonochemical method. The monophase of BaZrO3 was formed completely in short irradiation time without the calcination process. X-ray diffraction, Fourier transform and Raman spectroscopy were used to characterize formation of the perovskite BaZrO3 phase, which occurs in a 60 minute single phase with a cubic crystal structure at room temperature. Therefore, sonochemical irradiation could accelerate the formation of BaZrO3 particles significantly. Furthermore, scanning electron microscopy investigated the uniform shape and size. The size distribution became narrow with increasing time, as a function of irradiation.

Influence of Mn Doping on the Magnetic Properties of CoFe2O4

A series of CoFe2−x Mn x O4 ceramics were synthesized successfully by conventional solid state reaction. The X-ray diffraction analysis proved that all samples were found to have a cubic spinel structure. Diffractograms were used for Rietveld refinement to determine lattice parameters, of which lattice parameter increased with increasing Mn concentration. The microstructure of the samples was studied using scanning electron microscopy. The vibrating sample magnetometer measurements showed that the highest saturated magnetization of 118.11 emu/g and coercivity of 46.89 Oe were observed in CoFe1.85Mn0.15O4 ceramic. Furthermore, X-ray absorption spectra of the samples were recorded to determine the Co, Fe and Mn valence states and their preferentially sites of the spinel structure.

Study on thermal transformation of CuHPO4·H2O obtained by acetone-mediated synthesis at ambient temperature

Copper hydrogenphosphate monohydrate, CuHPO4·H2O, was synthesized for the first time through simple and rapid method using the mixing of copper carbonate and phosphoric acid in acetone medium at ambient temperature. The obtained CuHPO4·H2O decomposed in three stages via dehydration and deprotonated hydrogenphosphate reactions, revealed by TG/DTG and DSC techniques. The kinetic triplet parameters (Ea, A, and n) and thermodynamic functions (ΔH*, ΔG*, and ΔS*) for the first two decomposed steps were calculated from DSC data. All the obtained functions indicate that the deprotonated HPO42− reaction for the second step occurs at a higher energy pathway than the dehydration reaction for the first step. The calculated wavenumbers based on DSC peaks were comparable with FTIR results, which support the breaking bonds of OH (H2O) and P-OH (HPO42−) according to decomposed mechanisms. All the calculated results are consistent and in good agreement with CuHPO4·H2O’s thermal transformation mechanisms.

Dielectric Properties and Characterizations of Binary Cu(2-x)MgxP2O7 Pyrophosphates

Samples of the binary metal pyrophosphate, Cu(2-x)Mg(x)P2O7 (x = 0.00 – 2.00), were prepared via solid state reaction. Vibrational bands of [P2O7]4− anion which contains the O–P–O radical ([PO2]−) and the P–O–P bride ([OPO]−) and approximate M–O stretching were identified by Raman scattering. A strong P–O–P band was observed clearly in Raman spectra, which indicated the formation of solid solution.The purity of synthetic powders were characterized by X-ray diffraction (XRD).The XRD patterns indicated that all the samples exhibited a single monoclinic phase structure. The complete solid solutions in the Cu(2-x)Mg(x)P2O7 (x = 0.00 – 2.00) system were obtained. The unit cell volume changed, due to the difference between the final product structure and Cu2P2O7.X-ray absorption near the edge structure (XANES) technique was used to confirm oxidation state of copper in the Cu(2-x)MgxP2O7.The relative permittivity and dielectric loss of the samples were measured. The bond length and bond angle were analyzed by EXAFS and Raman techniques. The relative permittivity was seen to maintain temperature by substituting Mg2+ with Cu2P2O7. These results were used to explain the crystal structure of materials in order to change the bond which affects dielectric phenomena.

Correlation between the chromaticity, dielectric properties and structure of the binary metal pyrophosphates, Cu(2−x)ZnxP2O7

The binary metal pyrophosphates, Cu(2−x)ZnxP2O7; x = 0.50–1.50, were synthesized via solid state reaction in order to obtain information on their solid solution phase formation. Characteristic peaks of the β-phase were detected under UV/Vis light emission in the range of 1200–1250 cm−1. The P2O74− ion, analyzed through vibration, carried the O–P–O radical, P–O–P bridge, and approximate M–O bond stretching, and was identified using Raman and Fourier transform infrared (FT-IR) spectra. The corrected dielectric constant (er) of the samples showed a similar value when Cu2+ was replaced by Zn2+ in the Cu2P2O7 structure. However, a slightly decreasing er could still be seen when the component x increased. The color of the samples with x = 0.00–1.50 exhibit a greenish hue, except for the composition with x = 2.00, which presents a colourless powder. The CIE chromaticity coordinates of Cu(2−x)ZnxP2O7; x = 0.50 to 1.50, shifted from (0.303, 0.366) to (0.292, 0.388), thus corresponding to a visible wavelength that shifted from about 506 to 512 nm, and 561 nm for x = 0.00. The phenomena of both dielectric and optical properties resulted from the changing crystal structure of the respective P2O74− cluster and octahedral M–O6 site. Investigation of the crystal structure was carried out by using Rietveld refinement analysis, with support from the extended X-ray absorption fine structure (EXAFS) fitting technique. Furthermore, this study revealed the relationships for binary metal pyrophosphates between their structure and dielectric properties, and the correlation between their structure and optical properties, which was confirmed by the reduction in chemical bonding, bond angle, number of clusters, and distortion of the octahedral MO6.

Structural and Magnetic Properties of Zn Doped CoFe2O4

Zinc doped cobalt ferrite powders were prepared by the solid state reaction method. The effect of zinc substitution on structure, morphology and magnetic properties was investigated. The X-ray analysis confirmed existence of the single phase cubic spinel structure, while Rietveld refinement data showed increasing of lattice parameters with zinc content. In addition, saturated magnetization increased with increasing zinc concentration and it was contained at maximum in CoFe1.9Zn0.1O4 powders. However, the value of coercivity was decreased with zinc doped content. Furthermore, the oxidative states were characterized by X-ray absorption spectroscopy. The results confirm that the structure contained Co2+, Fe3+ and Zn2+ ions.

The Effect of Zirconium on the Perovskite Phase Formation of Barium Zirconium Titanate Nanoparticles by the Sonochemical Method

The sonochemical technique is a powerful synthetic method for the production of nanostructured inorganic powders. Monosized spherical barium zirconium titanate [Ba(ZrxTi1-x)O3; BZT], with x = 0.00, 0.05, 0.20 and 0.40 nanoparticles, were synthesized successfully through sonochemical reaction. The phase formation as well as crystal structure and morphology were investigated. The as-prepared powders were identified by X-ray diffraction (XRD). The cubic perovskite structure of BZT was formed completely in a short irradiation time without the calcination process. The lattice parameter (a) of the samples increased with increasing zirconium concentration. Furthermore, when the concentration of zirconium increased, the reaction time must be increased in order to obtain phase-pure perovskite. The BZT nanoparticles showed a monosized spherical shape that was different from that in other preparation methods. The morphology of the products was very close to spherical, with the particle size distribution being rather narrow.

X-ray Absorption Spectroscopy Studies of Cu(2-x)ZnxP2O7 Binary Pyrophosphates

Binary metal pyrophosphates; Cu(2-x)ZnxP2O7 (x = 0.0–2.0) compounds, were prepared via the solid solution method. The synthesize powders were characterized by X-ray diffraction (XRD). The local structure of Cu was analyzed by the mean of synchrotron X-ray absorption near the edge structure (XANES). The Cu2+-O1, Cu2+-O2 and Cu-Cu/Zn distances determined are extended X-ray absorption fine structure (EXAFS) measurements at the Cu K-edge, with a distance of about 1.52, 2.11, and 2.74 Å. The correlation between the structural changes and Cu content was analyzed and discussed. The analysis of the EXAFS spectra collected at the Cu K-edge indicates that the local structure around Cu atoms also is affected by the introduction of Zn atoms in the structure.