Phyllosilicate minerals as an effective additive to an M-1/EMD/M-2 humidity sensing system

It was found that the phyllosilicate minerals exhibited a new function to markedly improve the performance of the Pt/EMD/Cu or Al humidity sensing element, which otherwise responded only to high humidity regions. The response time profiles of the galvanic potentials produced depended on the nature of the additives, and kaolinite and muscovite enhanced the humidity sensing characteristics of EMD, showing good linearity and a fast response. The discrepancy between the theoretical and observed galvanic potentials was explained in terms of steric hindrance, diminished concentration of protons, mixed potential and mixed ionic and electronic conduction of the materials involved. A mechanism whereby the humidity sensing characteristics was enhanced has been proposed taking into account the role of interlayer water molecules present in the EMD-additive system.