Solid state humidity sensor

Details Solid state humidity sensor Solid state humidity sensor

1997-04-29

1999-01-05

Snay, Jeffrey

Chemical apparatus and process disinfecting, deodorizing, preser

Analyzer, structured indicator, or manipulative laboratory...

Means for analyzing gas sample

422 90, G01N 2712

Patent

active

058558497

ABSTRACT:
A method for forming a solid state humidity sensor is disclosed which comprises the steps of: (a) dissolving a tungstate salt into an aqueous solution; (b) adjusting the pH of the aqueous tungstate salt solution to below 8.5; (c) forming one or a pair of electrodes on an insulating substrate; (d) placing the substrate into the pH-adjusted aqueous tungstate salt solution and heating the aqueous solution containing the substrate at temperatures above 70.degree. C. to thereby form a pyrochlore-type crystalline tungsten trioxide film over the electrode or pair of electrodes; and (e) forming another electrode over the pyrochlore-type crystalline tungsten trioxide film if only one electrode is formed during step (c). Alternatively, the pyrochlore-type crystalline tungsten trioxide film can be formed over or between the electrodes by heating the pH-adjusted aqueous tungstate salt solution to cause a precipitation of pyrochlore-type crystalline tungsten trioxide, then screen-printing the pyrochlore-type crystalline tungsten trioxide powder on one or both of the electrodes to thereby form a humidity sensing element. The pyrochlore-type crystalline tungsten trioxide is represented by the general formula of (M.sub.2 O).sub.x WO.sub.3.zH.sub.2 O, in which M is a cation, x is about 0.5, and z, which is the amount of crystalline water contained in the crystal, is typically less than 2.

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Nedjar, R. et al "A new form of tungsten trioxide: tungsten trioxide and tungsten trioxide homihydrate with pyrochlore structure" Materials Research Bulletin, vol. 23, No. 1 (1988) pp. 91-97.

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