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- Author or Editor: Y. Sawada x
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Conflicting results have been reported by different workers on the thermal decomposition of silver carbonate, Ag2CO3. In the present study, the decomposition mechanism was elucidated by various analytical methods; gas analysis (differential thermal gas analyses) in helium, carbon dioxide and oxygen flows with and without a P2O5 trap or a KOH trap, DTA-TG in a carbon dioxide flow and high-temperature X-ray diffraction analysis in a carbon dioxide flow.
Abstract
The influence of thermal process for indium hydroxoformate, In(OH)(HCO2)2, used as one of the precursor material of ITO transparent conducting films, has been successfully investigated in some controlled atmospheres by unique thermal analyses equipped with a humidity generator, which are thermogravimetry - differential thermal analysis (TG-DTA), thermogravimetry in conjunction with evolved gas analysis using mass spectrometry (TG-MS) and simultaneous measurement of differential scanning calorimetry and X-ray diffractometry (XRD-DSC). The thermal process in dry gas atmosphere by linear heating experiment was indicated through a single-step reaction between 200 and 300C, while the thermal process in the atmosphere of controlled humidity proceeded through two-step reactions and the formation of crystalline indium oxide (In2O3) was effectively promoted and completed at the lower temperatures with introducing water vapor in the atmosphere. The thermal process changed dramatically by introducing water vapor and was quite different from that in dry gas atmosphere. Pure In2O3 was synthesized in inert atmosphere of controlled humidity and could be easily formed at temperatures below 260C. The XRD-DSC equipped with a humidity generator revealed directly the crystalline change from In(OH)(HCO2)2 to In2O3 and the formation of the intermediate during the thermal decomposition. A detailed thermal process of In(OH)(HCO2)2 and the effect of heating atmosphere are discussed.
Formation process of indium oxide transparent conducting films via thermal decomposition
Nanostructure observation of dip-coated films during electron-beam irradiation
Abstract
Indium 2-ethylhexanoate monohydroxide, In(OH)(O2CCH(CH2CH3)(CH2)3CH3)2, is a precursory material to fabricate In2O3-based transparent conducting films by dip-coating process. Formation process of indium oxide transparent conducting films was investigated using an ultra-low acceleration voltage FE-SEM. The nanostructure change of the precursory layer was observed during the electron beam irradiation in vacuum. A flat and homogeneous surface of the as-coated layer changed to porous and net-work like nanostructure after 80 s; the pore diameter increased and the pore distance decreased although the number of pores remained unchanged. These processes were interpreted as the preliminary step to form porous films composed of nm-sized inter-linked oxide particles as reported in the previous papers by the authors.
DSC of as-deposited thin films dip-coated on the substrate
Thermal change of indium(III) 2-ethylhexanoate to form In2O3 thin films
Abstract
The formation process of a ceramic (indium oxide) thin film (thickness: approximately 20 nm to several microns) was investigated by thermal analyses. Thermal changes of an organic precursor, indium(III) 2-ethylhexanoate, dip-coated on a glass substrate was successfully detected by DSC in air. Exothermic phenomena were observed at marked lower temperatures for the thin films than for the bulk material; thinner films had slightly lower peak temperatures. The reaction mechanism is discussed with reference to mass spectra of the evolved gases.
Summary The size effect on the crystal structure including the chemical bonding nature has been investigated for several kinds of BaTiO3 nanopowder with the particle sizes down to 50 nm in diameter, by means of powder diffraction using high-energy synchrotron radiation. The Rietveld refinement reveals that the BaTiO3 nanopowder consists of tetragonal and cubic structure components at 300 K. The feature of coexistence can be illustrated by the core/shell model for the particle, in which the shell with a cubic structure covers the core with a tetragonal structure. The thickness of the cubic shell is almost constant irrespective of the particle sizes, and is estimated as approximately 8 nm. Hence, the critical particle-size, where the entire particle is covered with the cubic shell, is suggested as 16 nm. The charge density distributions of the BaTiO3 nanopowder in the cubic phase at 410 K are revealed by the maximum entropy method. Changes in the bonding electron density and the ionic valence expected are not observed clearly even in the 50 nm crystal compared with the bulk crystal.
Abstract
Zinc formate dihydrate has been synthesized and characterized by powder X-ray diffraction, elemental analysis, FTIR spectra and thermal analysis. The molar heat capacity of the coordination compound was measured by a temperature modulated differential scanning calorimetry (TMDSC) over the temperature range from 200 to 330 K for the first time. The thermodynamic parameters such as entropy and enthalpy vs. 298.15 K based on the above molar heat capacity were calculated. The thermal decomposition characteristics of this compound were investigated by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). TG curve showed that the thermal decomposition occurred in two stages. The first step was the dehydration process of the coordination compound, and the second step corresponded to the decomposition of the anhydrous zinc formate. The apparent activation energy of the dehydration step of the compound was calculated by the Kissinger method using experimental data of TG analysis. There are three sharply endothermic peaks in the temperature range from 300 to 650 K in DSC curve.
Abstract
Resonant nuclear inelastic scattering (NIS) spectra of (Sr,Ca)(Fe,Co)O3- d and (Ba,Ca)(Fe,Co)O3- d were measured with the energy resolution of 3.5 MeV by detecting the 6.3 keV Fe Ka X-rays following after Mössbauer effect on 57Fe transition excited by the monochromatized 14.41 keV synchrotron radiation. Both series of oxides annealed in air and in CO2 were examined. Soft phonon peak arising at ~8 MeV in NIS spectra of (Sr0.5Ca0.5)(Fe0.5Co0.5)O3- d and (Ba0.5Ca0.5)FeO3- d was found to be correlated with the oxygen ordering into brownmillerite structure, whereas more complex multi-phonon structure was observed in the spectra of less oxygen-deficient oxides such as (Sr0.95Ca0.05)(Fe0.5Co0.5)O3- d and (Sr0.7Ca0.3)(Fe0.5Co0.5)O3- d showing rather random distrubution of the oxygen vacancies. The changes in phonon DOS after CO2 absorbtion were also detected. Lam-Mössbauer factors of these oxides were calculated on the base of Debye Model.
Abstract
Pb(1,4-BDC)·(DMF)(H2O) (1,4-BDC=1,4-benzenedicarboxylate; DMF=dimethylformamide) has been synthesized and investigated by elemental analysis, FTIR spectroscopy, thermogravimetry (TG), derivative thermogravimetry (DTG). TG-DTG curves show that the thermal decomposition occurs in four stages and the corresponding apparent activation energies were calculated with the Ozawa-Flynn-Wall (OFW) and the Friedman methods. The most probable kinetic model function of the dehydration reaction of the compound has been estimated by the Coats-Redfern integral and the Achar-Bridly-Sharp differential methods in this study.
Abstract
Fluorine-doped tin dioxide (FTO) films were deposited on silicon wafers by inverted pyrosol technique using solutions with different doping concentration (F/Sn=0.00, 0.12, 0.75 and 2.50). The physical and electrical properties of the deposited films were analyzed by SEM, XRF, resistivity measurement by four-point-probe method and Hall coefficient measurement by van der Pauw method. The electrical properties showed that the FTO film deposited using the solution with F/Sn=0.75 gave a lowest resistivity of 3.210–4 ohm cm. The FTO films were analyzed by temperature programmed desorption (TPD). Evolved gases from the heated specimens were detected using a quadruple mass analyzer for mass fragments m/z, 1(H+), 2(H2 +), 12(C+), 14(N+), 15(CH3 +), 16(O+), 17(OH+ or NH3 +), 18(H2O+ or NH4 +), 19(F+), 20(HF+), 28(CO+ or N2 +), 32(O2 +), 37(NH4F+), 44(CO2 +), 120(Sn+), 136(SnO+) and 152(SnO2 +). The majority of evolved gases from all FTO films were water vapor, carbon monoxide and carbon dioxide. Fluorine (m/z 19) was detected only in doped films and its intensity was very strong for highly-doped films at temperature above 400C.
