Exploration of Fast Proton Conductors and their Application to New Type Chemical Sensors

点击翻译按钮获取中文摘要

Protonic conducting solid electrolytes (proton conductors) have a remarkable characteristic that only hydrogen ions (protons) can move through the solid material as electrical carriers. By using this property of proton conductors, these materials can be applied to new functional devices in place of conventional liquid electrolytes. Especially in the case of chemical sensors, the use of proton conductors can make it possible to develop new types of all-solid-state chemical sensors, such as cordless sensors, micro sensors, and intelligent sensors. In this study, we first conducted to explore excellent proton conductors with high ionic conductivity as well as high stability, and to clarify the conduction mechanism of proton conductors. Then, we tried to develop new type chemical sensors using proton conductors which can be operated at room temperature.The results obtained in this study are summarized as follows: (1) Among various inorganic ionexchangers examined, antimonic acid and antimo … More ny phosphate were found to have relatively high protonic conductivity and thermal- and chemical-stability. (2) The investigation of protonic conduction mechanism in antimonic acid clarified that the mechanism changed from a hopping-type to a Grotthus-type with an increase in the amounts of adsorbed water. (3) A four-probe type sensor element in which two silver probes were embedded was newly designed. The sensor signal (internal potential difference between two probes) was found to be not only insensitive to humidity but also proportional to hydrogen concentration in air. (4) In order to improve gas selectivity to CO in air of the proton conductor sensor, the use of oxide electrodes, such as WO_3 and SnO_2 in place of Pt electrode, was found to be very effective. (5) The amperometric proton conductor sensors using Nafion membrane and antimonic-acid thick-film could detect both gaseous oxygen and dissolved oxygen in water. These sensors would be applied to transducers of biosensors. (6) The sensor elements using antimonic-acid thick-film fabricated by means of screen-printing method or spin-coating method showed excellent sensing characteristics to H_2 in air at room temperature. Such a thick-film type sensor would be compatible to miniaturization as well as simplification. Less