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.
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.
Authors:Y. Sawada, K. Omika, Y. Ito, F. Muta, and M. Momota
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.
Authors:Y. Sawada, S. Nakazaki, S. Tachibana, Y. Nishimoto, and R. Ozao
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.
Authors:S. Aoyagi, Y. Kuroiwa, A. Sawada, H. Kawaji, and T. Atake
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.
Authors:J. Zhang, J. Zeng, Y. Liu, L. Sun, F. Xu, W. You, and Y. Sawada
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.
Authors:J. Zhang, Y. Liu, J. Zeng, F. Xu, L. Sun, W. You, and Y. Sawada
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.
Authors:K. Nomura, A. Rykov, T. Mitsui, Y. Yoda, Y. Kobayashi, M. Seto, and Ts. Sawada
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.
Authors:Z. Zhang, L. Sun, Z. Tan, F. Xu, X. Lv, J. Zeng, and Y. Sawada
The molar heat capacities of the room temperature ionic liquid 1-butylpyridinium tetrafluoroborate (BPBF4) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity
on temperature is given as a function of the reduced temperature X by polynomial equations, Cp,m [J K−1 mol−1]=181.43+51.297X −4.7816X2−1.9734X3+8.1048X4+11.108X5 [X=(T−135)/55] for the solid phase (80–190 K), Cp,m [J K−1 mol−1]= 349.96+25.106X+9.1320X2+19.368X3+2.23X4−8.8201X5 [X=(T−225)/27] for the glass state (198–252 K), and Cp,m[J K−1 mol−1]= 402.40+21.982X−3.0304X2+3.6514X3+3.4585X4 [X=(T−338)/52] for the liquid phase (286–390 K), respectively. According to the polynomial equations and thermodynamic relationship,
the values of thermodynamic function of the BPBF4 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition
of BPBF4 was observed at 194.09 K, the enthalpy and entropy of the glass transition were determined to be ΔHg=2.157 kJ mol−1 and ΔSg=11.12 J K−1 mol−1, respectively. The result showed that the melting point of the BPBF4 is 279.79 K, the enthalpy and entropy of phase transition were calculated to be ΔHm = 8.453 kJ mol−1 and ΔSm=30.21 J K−1 mol−1. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BPBF4 was determined to be ΔcHm0 = −5451±3 kJ mol−1. The standard molar enthalpy of formation of BPBF4 was evaluated to be ΔfHm0 = −1356.3±0.8 kJ mol−1 at T=298.150±0.001 K.