Abstract: A humidity sensor which varies in electrical impedance with variations in humidity in the atmosphere in which it is placed comprising a ceramic body, at least a pair of spaced electrodes disposed on said ceramic body in electrical contact therewith, and an electrical contact on each said electrode, said ceramic body being an electrolyte comprised of Na.sub.1+x Si.sub.x Zr.sub.2 P.sub.3-x O.sub.12, where x has a value ranging from 1.5 to 2.8, said ceramic body having a density of at least about 90% of the theoretical density for said Na.sub.1+x Si.sub.x Zr.sub.2 P.sub.3-x O.sub.12, each said electrode being in the form of a continuous interconnecting network which forms at least a sufficient plurality of non-linear recesses with the surface of the ceramic body exposing said ceramic body surface to said atmosphere to produce a measurable electrical impedance change when said atmosphere varies in relative humidity.

Abstract: Methods of forming a solid ion-conductive electrolyte are described which comprise providing a preformed thermoplastic polymer film, positioning a plurality of solid ion-conductive particles against one surface of the polymer film, positioning a deformable sheet against one surface of the film, positioning a deformable sheet against the particles and the opposite surface of the film, hot pressing the particles into the film and deforming the deformable sheets, cooling the film, and removing the deformed sheets, thereby forming a polymer film having ion-conductive particles exposed on opposite surfaces of the film.