Nanostructural design of electrically conductive ceramics and its application in gas sensors

Most of gas sensors are "surface type" gas sensors that utilize only changes in physical properties near the surface of grains. In this paper, the concept of "non-surface type" gas sensors that utilize changes in physical properties throughout the entire grain is proposed. In particular, we focused on a resistive oxygen sensor as one type of "non-surface type" gas sensor, and achieved notable performance with high-speed response to the order of milliseconds in addition to elucidating details of the response mechanism and investigating the stability of the sensor, which is a substantial advantage of "non-surface type" gas sensors. Next, we demonstrated the extension to flammable gas sensors by incorporating a flammable gas-reactive layer into the resistive oxygen sensor. Furthermore, in order to achieve highly sensitive and highly selective "non-surface type" gas sensors, a new sensor material was developed consisting of alternating layers at the molecular level of an inorganic layer to perform the signal conversion function and an organic layer to perform the molecular recognition function. Aldehyde gases were detected selectively by appropriate nanostructural design of the new material.