Papers - SAKAI Go
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Preparation of Cr-doped TiO<inf>2</inf>thin film of p-type conduction for gas sensor application
Ruiz A., Cornet A., Sakai G., Shimanoe K., Morante J., Yamazoe N.
Chemistry Letters ( 9 ) 892 - 893 2002.9
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters
Titanium dioxide (TiO2) could be doped with as much as 8.7 atom% Cr by means of a sol-gel method. XRD analysis revealed that the powder of Cr (8.7 atom%)-doped TiO2calcined at 500°C consisted of small crystallites ascribale to anatase structure. The thin film of doped TiO2(70μm) at this composition was found to behave as a p-type semiconductor on exposure to CO and NO2in air: it responded to dilute NO2with a sharp decrease in electrical resistance.
DOI： 10.1246/cl.2002.892
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Preparation of Cr-Doped TiO2 Thin Film of p-type Conduction for Gas Sensor Application Reviewed
共著者：A. Ruiz, A. Cornet, G. Sakai, K. Shimanoe, J. R. Morante, N. Yamazoe
Chemistry Letters, No. 9, 892-893 9 892 - 893 2002.9
Language：English Publishing type：Research paper (scientific journal)
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Importance of Gas Diffusion in Semiconductor Gas Sensor
共著者：N. Yamazoe, G. Sakai, N. Matsunaga, N. -S. Baik, K. Shimanoe
Chemical Sensors for Hostile Environments Ceramic Transactions,Vol. 130, 27-36 130 27 - 36 2002.4
Language：English Publishing type：Research paper (scientific journal)
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Diffusion equation-based study of thin film semiconductor gas sensor-response transient
Matsunaga N., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 83 ( 1-3 ) 216 - 221 2002.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
A diffusion-reaction equation has been formulated and solved under non-steady condition in order to simulate how the gas concentration profile develops inside a thin film of semiconducting oxide after its exposure to a target gas. The gas concentration can be expressed by a polynomial function involving diffusion coefficient (D), rate constant (k), film thickness (L), depth from the film surface (x), time (t) and target gas concentration outside (Cs). Remarkably, the gas concentration at a given x exhibits overshooting behavior before reaching a steady value, the magnitude and appearance time of the overshooting being very dependent on x, k and L/D1/2. The overshooting appears as a result of the competition between diffusion and reaction. Two types of overshooting are recognized, which are ascribable to the gas molecules having entered from the surface and to those having reflected by the wall of substrate, respectively. Reflecting such an overshooting in gas concentration, the response transient also exhibits an overshooting phenomenon. © 2002 Elsevier Science B.V. All rights reserved.
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High temperature PTC thermistor using Ba cobaltite
Kinoshita K., Kusaba H., Sakai G., Shimanoe K., Miura N., Yamazoe N.
Chemistry Letters ( 3 ) 412 - 413 2002.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters
It was found that partially Fe-substituted Ba cobaltite, BaCo0.7Fe0.3O3-δ, shows sharp PTC behavior at temperature above 850 °C. As revealed by XRD measurements, the PTC behavior is accompanied by phase transformation between hexagonal perovskite structure (low temperature) and cubic one (high temperature).
DOI： 10.1246/cl.2002.412
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Kinoshita K., Kusaba H., Sakai G., Shimanoe K., Miura N., Yamazoe N.
Chemistry Letters ( 3 ) 344 - 345 2002.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters
Oxygen permeation property of A-site partially substituted barium cobaltites, A′xBa1-xCo0.7Fe0.3O3-δ(A′ = Ba, Pr, Gd, Dy, Y and Yb), were examined. Substitution of Ba by Dy, Y or Yb was found to stabilize cubic perovskite structure even when x remained as small as 0.05. As a result, oxygen permeation through the disks made of these oxides appeared at temperature lower than 500 °C, and reached fairly high levels at elevated temperature.
DOI： 10.1246/cl.2002.344
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Miura N., Sasaki M., Sakai G., Vengatajalabathy Gobi K.
Chemistry Letters ( 3 ) 342 - 343 2002.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters
A regenerable surface plasmon resonance (SPR)-based immunosensor functioning with the indirect competitive immunoreaction of monoclonal antibody between the analyte (antigen) in testing solution and antigen-bovine serum albumin conjugate immobilized on immunoprobe provided a rapid in situ estimation (response time: about 15 min) of benzo(a)pyrene in the concentration range of 0.1-300 ppb.
DOI： 10.1246/cl.2002.342
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Temperature-swing based oxygen enrichment by using perovskite-type oxides
Kusaba H., Sakai G., Shimanoe K., Yamazoe N., Miura N.
Journal of Materials Science Letters 21 ( 5 ) 407 - 409 2002.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Materials Science Letters
A temperature-swing-adsorption method was established as a new oxygen-enriching method. The resulting method combines oxygen-absorptive properties of perovskite type oxides and waste heat from high temperature processes. The feasibility of the new method was explored using a family of partially substituted strontium cobaltites.
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Temperature-swing based oxygen enrichment by using perovskite-type oxides Reviewed
共著者：H. Kusaba, G. Sakai, K. Shimanoe, N. Miura, N. Yamazoe
Journal of Materials Science Letters,Vol. 21, 407-409 21 407 - 409 2002.3
Language：English Publishing type：Research paper (scientific journal)
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Diffusion equation-based study of thin film semiconductor gas sensor -response transient- Reviewed
共著者：N. Matsunaga, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, Vol. 83, 216-221 83 216 - 221 2002.3
Language：English Publishing type：Research paper (scientific journal)
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High Temperature PTC Thermistor Using Ba Cobaltite Reviewed
共著者：K. Kinoshita, H. Kusaba, G. Sakai, K. Shimanoe, N. Miura, N. Yamazoe
Chemistry Letters, No.3, 412-413 ( 3 ) 412 - 413 2002.3
Language：English Publishing type：Research paper (scientific journal)
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Influences of A-site Partial Substitution for BaCo0.7Fe0.3O3 Oxide on Perovskite Structure and Oxygen Permeability Reviewed
共著者：K. Kinoshita, H. Kusaba, G. Sakai, K. Shimanoe, N. Miura, N. Yamazoe
Chemistry Letters, No.3, 344-345 3 344 - 345 2002.3
Language：English Publishing type：Research paper (scientific journal)
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Regenerable surface plasmon resonance (SPR)-based immunosensor for highly sensitive measurement of sub-ppb levels of benzo(a)pyrene
共著者：N. Miura, M. Sasaki, G. Sakai, K. V. Gobi
Chemistry Letters, No.3, 342-343 2002 ( 3 ) 342 - 343 2002.3
Language：English Publishing type：Research paper (scientific journal)
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Theory of gas-diffusion controlled sensitivity for thin film semiconductor gas sensor
Sakai G., Matsunaga N., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 80 ( 2 ) 125 - 131 2001.11
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Influences of gas transport phenomena on the sensitivity of a thin film semiconductor gas sensor were investigated theoretically. A diffusion equation was formulated by assuming that an inflammable gas (target gas) moves inside the film by Knudsen diffusion, while it reacts with the adsorbed oxygen following a first-order reaction kinetic. By solving this equation under steady-state conditions, the target gas concentration inside the film was derived as a function of depth (x) from the film surface, Knudsen diffusion coefficient (DK), rate constant (k) and film thickness (L). The gas concentration profile thus obtained allowed to estimate the gas sensitivity (S) defined as the resistance ratio (Ra/Rg), under the assumption that the sheet conductance of the film at depth x is linear to the gas concentration there with a proportionality constant (sensitivity coefficient), a. The derived equation shows that S decreases sigmoidally down to unity with an increase in L√k/DK. Further by assuming that the temperature dependence of rate constant (k) and sensitivity coefficient (a) follows Arrenius type ones with respective activation energies, it was possible to derive a general expression of S involving temperature (T). The expression shows that, when the activation energies are selected properly, the S versus T correlation results in a volcano-shaped one, its height increasing with decreasing L. The dependence of S on L at constant T as well as on T at constant L can thus be simulated fairly well based on the equation. © 2001 Elsevier Science B.V. All rights reserved.
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Theory of Gas-diffusion Controlled Sensitivity for Thin Film Semiconductor Gas Sensor Reviewed
共著者：G. Sakai, N. Matsunaga, K. Shimanoe, N. Yamazoe
Sensors and Actuators B,Vol. 80, 125-131 80 125 - 131 2001.11
Language：English Publishing type：Research paper (scientific journal)
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Sakai G., Baik N., Miura N., Yamazoe N.
Sensors and Actuators, B: Chemical 77 ( 1-2 ) 116 - 121 2001.6
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Thin film SnO2sensors with various thicknesses were spin-coated from a hydrothermally treated SnO2sol suspension. The FE-SEM observation revealed that the films prepared from the 1.8 wt.% SnO2containing sol suspension had good uniformity packed with nano-crystalline SnO2even after calcination at 600°C when its thickness was up to about 300 nm, though many cracks were observed for thicker films. The gas sensing characteristics to H2and CO were evaluated as a function of film thickness (80-300 nm) in dry air. The electrical resistance of thin films decreased monotonically with increasing film thickness. It was found that the sensor response to H2similarly decreased with an increase in film thickness, while the CO response was found to be almost independent of the film thickness. The relationship between gas sensing properties and film thickness was discussed on the basis of diffusivity and reactivity of the gases inside the oxide films. © 2001 Elsevier Science B.V.
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Metal oxide semiconductor N<inf>2</inf>O sensor for medical use
Kanazawa E., Sakai G., Shimanoe K., Kanmura Y., Teraoka Y., Miura N., Yamazoe N.
Sensors and Actuators, B: Chemical 77 ( 1-2 ) 72 - 77 2001.6
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
In order to develop a semiconductor type gas sensor applicable to the monitoring of N2O in air, a search for the semiconducting oxides sensitive to N2O was carried out. Among the 23 kinds of single oxides tested, SnO2turned out to give the highest sensitivity to N2O, although the sensitivity was not high enough. The N2O sensitivity was found to be promoted effectively when SnO2was loaded with a small amount of a basic oxide such as SrO, CaO, BaO, Bi2O3and Sm2O3. The promotion was particularly conspicuous with SrO loading. For example, 0.5wt.% SrO-loaded SnO2, exhibited the N2O sensitivity about three times as high as that of pure SnO2, and could detect N2O in air fairly well in the concentration range of 10-300 ppm at 500°C. © 2001 Elsevier Science B.V.
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Metal Oxide Semiconductor N2O Sensor for Medical Use Reviewed
共著者：E. Kanazawa, G. Sakai, K. Shimanoe, Y. Kanmura, Y. Teraoka, N. Miura, N. Yamazoe
Sensors and Actuators B, Vol. 77, 72-77 77 72 - 77 2001.6
Language：English Publishing type：Research paper (scientific journal)
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Gas sensing properties of tin oxide thin films fabricated from hydrothermally treated nanoparticles -Dependence of CO and H2 response on film thickness- Reviewed
共著者：G. Sakai, N. S. Baik, N. Miura, N. Yamazoe
Sensors and Actuators B, Vol. 77, 116-121 77 116 - 121 2001.6
Language：English Publishing type：Research paper (scientific journal)
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Preparation of Stabilized Nano-size Tin-Oxide Particles by Hydrothermal Treatment Reviewed
共著者：N.-S. Baik, G. Sakai, N. Miura, N. Yamazoe
Journal of the American Ceramic Society, Vol. 83,No. 12, 2983-2987 83 ( 12 ) 2983 - 2987 2000.12
Language：English Publishing type：Research paper (scientific journal)