Budget Amount *help |
¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 1999: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1998: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1997: ¥1,200,000 (Direct Cost: ¥1,200,000)
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Research Abstract |
The 90% response time (tィイD290ィエD2) of the ambient temperature, solid-state oxygen sensors, [Ag|AgィイD26ィエD2IィイD24ィエD2WOィイD24ィエD2|PbSnFィイD24ィエD2|Sensing Electrode(SE) [conductive whisker material(CWM)-iron phthalocyanine(FePc)-PbSnFィイD24ィエD2] has been improved, and the mechanism of fast response has been elucidated. Furthermore, we also establish guidelines for the optimal design of the SE-mixtures and explore novel applications other than OィイD22ィエD2-sensing. As a result, the following findings were obtained. 1.Effects of the morphology of SE-materials The tィイD290ィエD2 and transient characteristics were found to depend on the aspect ratio, smoothness of surface, conductivity and particle size of the incorporated CWM and PbSnFィイD24ィエD2 rather than their chemical properties. Fast response(-25 s) was realized by incorporating CWMs and thin PbSnFィイD24ィエD2 plates with a size of -20 μm. 2.Relation between the mixed state of the SE-mixtures and response properties From SEM-EDX observation of th
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e mixed state including the special distribution of the three-phase boundaries (tpb) of CWM-PbSnFィイD24ィエD2-gas, it was found that tィイD290ィエD2 strongly depend on the network structure, in particular, the coarseness. 3.Elucidation of the mechanism and guidelines of the optimal design Oxygen molecules rapidly diffuse along the networks of CEM and thin PbSnFィイD24ィエD2 plates to the reduction site in the tpb and are reduced to 2O- after their dissociation on the Fe sites of FePc. Electrons also were equally easily delivered to the sites. This makes a rapid and simultaneous change of the electrochemical potentials of the uniform sites, resulting in fast response. The optimal design concept is as follows : 【encircled1】Selection of sheet- and whisker-like electrolytes and conductive materials capable to form simple networks 【encircled2】Selection of optimal OィイD22ィエD2 reduction catalysts (e.g., FePc, CoPc) 【encircled3】Optimization of the CWM : catalyst : electrolyte ratio. 4.New application The sensor could be applied to the screening of new oxygen-gas electrode materials. As the result of the screening, the brownmillerite SrCoOィイD22.5ィエD2 was found to be excellent electrode material, better than Pt. Less
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