Protonic conductivity of hydrotalcite-type compound thick films: Application to a humidity sensor
Abstract A new type of realization of the hydrotalcite-type lamellar protonic superconductor Zn 2 Al(OH) 6 Cl· n H 2 O (henceforth called [Zn-Al-Cl] is described, using an original ink composed of a concentrated aqueous suspension of [Zn-Al-Cl] which, when applied by the screen-printing technique, permits to elaborate very satisfactory deposits. X-ray patterns show a high orientation of the (001) reticular planes in a direction parallel to the substrate; this must produce a strong anisotropy of the material conductivity. The electrical properties related to the hydration of the [Zn-Al-Cl] compound are such as to permit the fabrication of a humidity sensor; two types of sensor are realized, one working with direct current (dc sensor), the other with alternating current (ac sensor). The performance of each device is studied by means of specific experiment. Results are interpreted and compared.