Yoshitsugu Tomokiyo - Academia.edu (original) (raw)
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Papers by Yoshitsugu Tomokiyo
まてりあ : 日本金属学会会報, Dec 20, 2001
Homogenized Nd-Fe-Co-B-Zr(-Ga) alloys are treated by hydrogenation (HD-process) and dehydrogenati... more Homogenized Nd-Fe-Co-B-Zr(-Ga) alloys are treated by hydrogenation (HD-process) and dehydrogenation (DR-process) with various treatment conditions, followed by quenching in argon gas flow. After the HDDR process, the specimens are crashed into powders. The magnetic properties of the powder and bonded magnets are measured with a vibrating sample magnetometer and a B-H tracer. The microstructural changes are also analyzed by electron microscopy (FE-SEM and TEM) and discussed with special reference to the behavior of boron.
Journal of Electron Microscopy, Dec 1, 1992
Convergent beam electron diffraction (CBED) provides more quantitative, precise and local informa... more Convergent beam electron diffraction (CBED) provides more quantitative, precise and local information on crystals than the traditional selected-area diffraction (SAD). Some of the results of our applications of CBED will be shown, with an emphasis on quantitative analyses of crystal structure in materials science: (i) The critical voltage and the intersecting Kikuchi line methods are combined with the CBED technique to accurately determine the structure factors and temperature factors; (ii) a large angle CBED is applied to determine the atomic coordinates in a unit cell; (iii) higher order Laue zone patterns are used to determine absolute lattice parameters and local lattice distortion
Scripta Materialia, Apr 1, 2003
Quantitative characterizations of nanostructures in FePt granular thin films were achieved by tra... more Quantitative characterizations of nanostructures in FePt granular thin films were achieved by transmission electron microscopy with various analytical methods. Significant amounts of Fe and Pt atoms are dissolved within the matrix of Al 2 O 3 in the as-deposited states. These solutioned Fe and Pt atoms play important roles of the structural changes during thermal annealing process.
Thin Solid Films, Aug 1, 2004
The crystallographic orientation relationships and the formation process of β-FeSi2/Si(001) films... more The crystallographic orientation relationships and the formation process of β-FeSi2/Si(001) films were investigated by transmission electron microscopy. A film produced by sputtering pure iron onto a silicon substrate at 600 °C consists of α- and β-FeSi2 particles. The crystallographic relationships obtained are: (112)α‖(111)Si and (101)β‖(111)Si or (110)β‖(111)Si. The grains of α- and β-FeSi2 grown inside the substrate adopt the epitaxy to Si(111), irrespective of the surface orientation of the substrate. At 500 °C, on the contrary, there are few α-FeSi2 grains and some grains of β-FeSi2 with (100)β‖(001)Si [010]β‖[110]Si. These results demonstrate that the lower temperature and the higher Fe concentration suppress the formation of α-FeSi2 and promote the formation of β-FeSi2 on/below the substrate surface.
Journal of Microscopy, Jul 1, 2001
Ultramicroscopy, Nov 1, 1991
Abstract A new type of defect introduced during electron irradiation in an α-Al 2 O 3 single crys... more Abstract A new type of defect introduced during electron irradiation in an α-Al 2 O 3 single crystal has been investigated through in situ high-resolution electron microscopy (HREM). The defects are observed as a black line contrast parallel to the (006) lattice plane in HREM images along the [110] direction but they are invisible in images along [001]. Line contrasts of the defects can also be observed in a bright-field or dark-field image under excitation of the systematic row of (006) reflection. Electron-diffraction patterns show streaks and extra spots suggesting the presence of planar defects inside the specimen as well as the surface. The defects do not appear during irradiation at 200 kV, but do appear at 400 kV after irradiation of several minutes. The defects occur in a thick area as well as in a thin area of specimen edge and some of them grow or disappear abruptly during irradiation. Examples of multi-layer and complex-layer defects are also shown.
Materials Transactions Jim, 1995
We will introduce the usefulness of convergent beam electron diffraction (CBED) in nanocharacteri... more We will introduce the usefulness of convergent beam electron diffraction (CBED) in nanocharacterization of materials: (1) Determination of local lattice strain in Si, (2) Determination of polarity of GaN of wurtzite structure , (3) Measurement of local oxygen concentration of the high T c superconductor YBa 2 Cu 3 O y .
Microscopy and Microanalysis, Aug 1, 2002
Indian Journal of Engineering and Materials Sciences, Aug 13, 2006
Thin films of InSb nanocrystals have been deposited onto KCl substrate using a thermal evaporatio... more Thin films of InSb nanocrystals have been deposited onto KCl substrate using a thermal evaporation technique under high vacuum conditions (∼10-6 torr). An intriguing microstructure consisted of moiré fringes with variable spacings and a corresponding variety of electron diffraction patterns in reciprocal space are reported at the deposition temperature of 373 K. The nanograins of InSb with preferred orientation and faceted morphology are delineated. A possible mechanism has been postulated to explain the evolution of such microstructures. It has been noticed that there is a peculiarity in the resistivity characteristics and infrared transmittance measurements obtained on these films. A set of electron micrographs, diffraction patterns and properties have been evaluated and discussed to understand the role of nanocrystals constituting the thin film, and certain types of defects introduced in the microstructure while deposition, on these properties.
Proceedings, annual meeting, Electron Microscopy Society of America, 1995
Effects of atomic thermal vibration in a crystal on the diffracted intensities is described by th... more Effects of atomic thermal vibration in a crystal on the diffracted intensities is described by the Debye-Waller factor (DWF). In general, DWF is a 3×3 symmetric matrix with six independent elements. For isotropic atomic vibration or atoms with cubic site symmetry, a single DWF B suffices: here s=sinθb/λ. DWFs are among the refined parameters in structure analysis in x-ray or neutron diffraction. The accuracy of DWF in such measurements often depends on the quality of the crystal. In quantitative electron diffraction, accurate DWF is needed for 1) converting Fourier coefficients of potential to that of charge density, 2) comparison with theoretical calculations of static crystals, 3) estimation of high order structure factor and absorption coefficients.DWF can be determined from measured amplitude of high order structure factors where the effects of bonding is minimal and DWF largest. Fig. 1 shows a plot of logrithmitic of ratios of measured MgO electron structure factors and calcula...
Journal of the Japan Institute of Metals, 1972
Proceedings, annual meeting, Electron Microscopy Society of America, 1990
The nonhomic property of ZnO-based varistors has been considered to depend on grain boundary stru... more The nonhomic property of ZnO-based varistors has been considered to depend on grain boundary structures. The microstructures of ulticomponent varistors are very complicated and quite sensitive to concentration and thermal history. It is not clear which microstructures play an important role for the electrical properties such as nonlinear coefficient and varistor voltage, and for the degradiation. In the present paper the microstructure of ZnO varistor was investigated by means of analytical electron microscopy to elucidate the relation between the microstructures and the electrical properties. In order to obtain local information on the microstructures of grain boundary and multiple junction, we combined the various TEM techniques such as high-resolution imaging (HREM), microprobe diffraction (μ ED), convergent-beam electron diffraction (CBED) and energy dispersive x-ray spectroscopy (EDX).ZnO varistor samples with addition of 0.5molZ% Bi2O3 + 0∼0.5molZ% CoO were prepared by convent...
Microscopy and Microanalysis, 2002
Proceedings, annual meeting, Electron Microscopy Society of America, 1990
A network of dark lines for higher order Laue zone (HOLZ) reflections often appears in the bright... more A network of dark lines for higher order Laue zone (HOLZ) reflections often appears in the bright-field disc of convergent beam electron diffraction under zone axis incidence. As geometry of the network (HOLZ pattern) depends sensitively on the crystal lattice parameters, the observation of HOLZ pattern has been applied to measure local change in the lattice parameters in various materials. The kinematical diffraction approximation has been usually employed in the analysis of observed HOLZ patterns, where the lattice parameters and the accelerating voltage exist as independent variables. However the positions of HOLZ lines depend also on the crystal potential for electrons, because the lines arise from intersections of dispersion spheres for the HOLZ reflections with the zeroth-order dispersion surface. In the kinematical analysis, an effective accelerating voltage Ee should be used in place of the actual one Ea, in order to compensate for line shift due to the dispersion effect.
まてりあ : 日本金属学会会報, Dec 20, 2001
Homogenized Nd-Fe-Co-B-Zr(-Ga) alloys are treated by hydrogenation (HD-process) and dehydrogenati... more Homogenized Nd-Fe-Co-B-Zr(-Ga) alloys are treated by hydrogenation (HD-process) and dehydrogenation (DR-process) with various treatment conditions, followed by quenching in argon gas flow. After the HDDR process, the specimens are crashed into powders. The magnetic properties of the powder and bonded magnets are measured with a vibrating sample magnetometer and a B-H tracer. The microstructural changes are also analyzed by electron microscopy (FE-SEM and TEM) and discussed with special reference to the behavior of boron.
Journal of Electron Microscopy, Dec 1, 1992
Convergent beam electron diffraction (CBED) provides more quantitative, precise and local informa... more Convergent beam electron diffraction (CBED) provides more quantitative, precise and local information on crystals than the traditional selected-area diffraction (SAD). Some of the results of our applications of CBED will be shown, with an emphasis on quantitative analyses of crystal structure in materials science: (i) The critical voltage and the intersecting Kikuchi line methods are combined with the CBED technique to accurately determine the structure factors and temperature factors; (ii) a large angle CBED is applied to determine the atomic coordinates in a unit cell; (iii) higher order Laue zone patterns are used to determine absolute lattice parameters and local lattice distortion
Scripta Materialia, Apr 1, 2003
Quantitative characterizations of nanostructures in FePt granular thin films were achieved by tra... more Quantitative characterizations of nanostructures in FePt granular thin films were achieved by transmission electron microscopy with various analytical methods. Significant amounts of Fe and Pt atoms are dissolved within the matrix of Al 2 O 3 in the as-deposited states. These solutioned Fe and Pt atoms play important roles of the structural changes during thermal annealing process.
Thin Solid Films, Aug 1, 2004
The crystallographic orientation relationships and the formation process of β-FeSi2/Si(001) films... more The crystallographic orientation relationships and the formation process of β-FeSi2/Si(001) films were investigated by transmission electron microscopy. A film produced by sputtering pure iron onto a silicon substrate at 600 °C consists of α- and β-FeSi2 particles. The crystallographic relationships obtained are: (112)α‖(111)Si and (101)β‖(111)Si or (110)β‖(111)Si. The grains of α- and β-FeSi2 grown inside the substrate adopt the epitaxy to Si(111), irrespective of the surface orientation of the substrate. At 500 °C, on the contrary, there are few α-FeSi2 grains and some grains of β-FeSi2 with (100)β‖(001)Si [010]β‖[110]Si. These results demonstrate that the lower temperature and the higher Fe concentration suppress the formation of α-FeSi2 and promote the formation of β-FeSi2 on/below the substrate surface.
Journal of Microscopy, Jul 1, 2001
Ultramicroscopy, Nov 1, 1991
Abstract A new type of defect introduced during electron irradiation in an α-Al 2 O 3 single crys... more Abstract A new type of defect introduced during electron irradiation in an α-Al 2 O 3 single crystal has been investigated through in situ high-resolution electron microscopy (HREM). The defects are observed as a black line contrast parallel to the (006) lattice plane in HREM images along the [110] direction but they are invisible in images along [001]. Line contrasts of the defects can also be observed in a bright-field or dark-field image under excitation of the systematic row of (006) reflection. Electron-diffraction patterns show streaks and extra spots suggesting the presence of planar defects inside the specimen as well as the surface. The defects do not appear during irradiation at 200 kV, but do appear at 400 kV after irradiation of several minutes. The defects occur in a thick area as well as in a thin area of specimen edge and some of them grow or disappear abruptly during irradiation. Examples of multi-layer and complex-layer defects are also shown.
Materials Transactions Jim, 1995
We will introduce the usefulness of convergent beam electron diffraction (CBED) in nanocharacteri... more We will introduce the usefulness of convergent beam electron diffraction (CBED) in nanocharacterization of materials: (1) Determination of local lattice strain in Si, (2) Determination of polarity of GaN of wurtzite structure , (3) Measurement of local oxygen concentration of the high T c superconductor YBa 2 Cu 3 O y .
Microscopy and Microanalysis, Aug 1, 2002
Indian Journal of Engineering and Materials Sciences, Aug 13, 2006
Thin films of InSb nanocrystals have been deposited onto KCl substrate using a thermal evaporatio... more Thin films of InSb nanocrystals have been deposited onto KCl substrate using a thermal evaporation technique under high vacuum conditions (∼10-6 torr). An intriguing microstructure consisted of moiré fringes with variable spacings and a corresponding variety of electron diffraction patterns in reciprocal space are reported at the deposition temperature of 373 K. The nanograins of InSb with preferred orientation and faceted morphology are delineated. A possible mechanism has been postulated to explain the evolution of such microstructures. It has been noticed that there is a peculiarity in the resistivity characteristics and infrared transmittance measurements obtained on these films. A set of electron micrographs, diffraction patterns and properties have been evaluated and discussed to understand the role of nanocrystals constituting the thin film, and certain types of defects introduced in the microstructure while deposition, on these properties.
Proceedings, annual meeting, Electron Microscopy Society of America, 1995
Effects of atomic thermal vibration in a crystal on the diffracted intensities is described by th... more Effects of atomic thermal vibration in a crystal on the diffracted intensities is described by the Debye-Waller factor (DWF). In general, DWF is a 3×3 symmetric matrix with six independent elements. For isotropic atomic vibration or atoms with cubic site symmetry, a single DWF B suffices: here s=sinθb/λ. DWFs are among the refined parameters in structure analysis in x-ray or neutron diffraction. The accuracy of DWF in such measurements often depends on the quality of the crystal. In quantitative electron diffraction, accurate DWF is needed for 1) converting Fourier coefficients of potential to that of charge density, 2) comparison with theoretical calculations of static crystals, 3) estimation of high order structure factor and absorption coefficients.DWF can be determined from measured amplitude of high order structure factors where the effects of bonding is minimal and DWF largest. Fig. 1 shows a plot of logrithmitic of ratios of measured MgO electron structure factors and calcula...
Journal of the Japan Institute of Metals, 1972
Proceedings, annual meeting, Electron Microscopy Society of America, 1990
The nonhomic property of ZnO-based varistors has been considered to depend on grain boundary stru... more The nonhomic property of ZnO-based varistors has been considered to depend on grain boundary structures. The microstructures of ulticomponent varistors are very complicated and quite sensitive to concentration and thermal history. It is not clear which microstructures play an important role for the electrical properties such as nonlinear coefficient and varistor voltage, and for the degradiation. In the present paper the microstructure of ZnO varistor was investigated by means of analytical electron microscopy to elucidate the relation between the microstructures and the electrical properties. In order to obtain local information on the microstructures of grain boundary and multiple junction, we combined the various TEM techniques such as high-resolution imaging (HREM), microprobe diffraction (μ ED), convergent-beam electron diffraction (CBED) and energy dispersive x-ray spectroscopy (EDX).ZnO varistor samples with addition of 0.5molZ% Bi2O3 + 0∼0.5molZ% CoO were prepared by convent...
Microscopy and Microanalysis, 2002
Proceedings, annual meeting, Electron Microscopy Society of America, 1990
A network of dark lines for higher order Laue zone (HOLZ) reflections often appears in the bright... more A network of dark lines for higher order Laue zone (HOLZ) reflections often appears in the bright-field disc of convergent beam electron diffraction under zone axis incidence. As geometry of the network (HOLZ pattern) depends sensitively on the crystal lattice parameters, the observation of HOLZ pattern has been applied to measure local change in the lattice parameters in various materials. The kinematical diffraction approximation has been usually employed in the analysis of observed HOLZ patterns, where the lattice parameters and the accelerating voltage exist as independent variables. However the positions of HOLZ lines depend also on the crystal potential for electrons, because the lines arise from intersections of dispersion spheres for the HOLZ reflections with the zeroth-order dispersion surface. In the kinematical analysis, an effective accelerating voltage Ee should be used in place of the actual one Ea, in order to compensate for line shift due to the dispersion effect.