| Project/Area Number |
12450270
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | Nagasaki University |
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Principal Investigator |
SHIMIZU Yasuhiro Nagasaki University, Graduate School of Science and Technology, Department of Materials Science, Associate Professor, 大学院・生産科学研究科, 助教授 (20150518)
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| Co-Investigator(Kenkyū-buntansha) |
HYODO Takeo Nagasaki University, Faculty of Engineering, Department of Materials Science and Engineering, Research Associate, 工学部, 助手 (70295096)
EGASHIRA Makoto Nagasaki University, Faculty of Engineering, Department of Materials Science and Engineering, Professor, 工学部, 教授 (60037934)
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| Project Period (FY) |
2000 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥15,000,000 (Direct Cost: ¥15,000,000)
Fiscal Year 2002: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2001: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2000: ¥11,500,000 (Direct Cost: ¥11,500,000)
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| Keywords | SnO_2-Cr_2O_3 / NO_x sensor / Zeta potential / Pd / TiO_2 / Anodic oxidation / H_2 sensor / WO_3 / SO_2 sensor / SnO_2 / 表面処理 / 界面接合状態 / SO_2 / バリスタ型ガスセンサ / 酸化スズ / 酸化クロム / p-n接合 / NO_x / ダブルショットキー障壁 / ブレークダウン電圧 |
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| Research Abstract |
The following four subjects have been mainly studied in this project, and the results obtained are summarized below.
I) Relationship between microstructure of grain-boundaries and NO_x, sensing properties of SnO_2-5Cr_2O_3 based varistor-type sensors
Microstructure and breakdown voltage in both air and N_2 have been investigated for SnO_2-Cr_2O_3 varistor-type sensors, in order to clarify the mechanism for higher NO sensitivity than No_2 observed for SnO_2-5Cr_2O_3. Increase in both NO and NO_2 gas sensitivity arose from the increase in the number of SnO_2-SnO_2 grain boundaries up to an additive amount of 5 wt% Cr_2Or_3. Stabilized NO chemisorption up to elevated temperatures owning to the formation of micro p-n junctions is considered to be responsible for the higher NO sensitivity.
2) NO_x, gas sensing properties of Nick film SnO_2-Cr_2O_3 as semiconductor gas sensors fabricated by slide-off transfer printing.
Relationship between ζ potential and NO_x, sensing properties has been studie
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d for thick film SnO_2-Cr_2O_3 fabricated by slide-off transfer printing as semiconductor gas sensors. SnO_2-Cr_2O_3 as semiconductor gas sensors showed tower NO sensitivity than NO_2, and achievement of higher NO sensitivity was limited for the varistor-type sensor. Ζpotential of SnO_2-Cr_2O_3 specimens increased abruptly from - 12 to +12 mV in the range of 0〜1.0wt% Cr_2O_3. In the case of SnO_2-Cr_2O_3 based specimens, it is considered that the SnO_2 surface acts as active sites for NO_2 detection, while micro p-n junctions for NO detection.
3) Development of an SO_2 gas sensor with high sensitivity and its sensing mechanism
Several metal oxides have been tested as thick film semiconductor SO_2 gas sensors. Among the oxides tested WO_2 was found to exhibit the highest sensitivity at 400℃, and further enhancement could be achieved by loading of 1.0 wt% Ag. From the detailed studies on the promotion effect induced by the Ag loading, resistance change of the sensor upon exposure to SO_2, is suggested to arise from the formation of SO_4^<2-> by the reaction between SO_2 and two O_2^- ad on the Loaded Ag.
4) Anodically oxidized TiO_2 film contacted with Pd electrode as diode-type H_2 sensor
Anodically oxidized TiO_2 films have been prepared, and they H_2 sensing properties have been tested, as an approach for realizing high sensing performance by controlling microstructure at the interface between sensor and electrode materials. The TiO_2 film contacted with Pd electrode showed diode-type current-voltage characteristics and reversible H_2 response in both air and N_2. Higher H_2 response was achieved in N_2 than in air under reverse bias conditions. The reversible H_2 response in N_2 is considered to arise from the change in barrier height at Pd/TiO_2 interface induced by dissociation of H_2 at the Pd surface and subsequent dissolution of H atoms into Pd bulk used for the electrode. Such a unique sensor will be used for H_2 detection under special environments containing no oxygen. Less
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