A study on the humidity sensing properties of ZnCr2O4–K2CrO4 ionic conductive ceramic sensor

The response to humidity of ZnCr2O4–K2CrO4 ceramic composites formed by solid-state reaction at elevated temperatures is studied. The fired ceramic body, which proved to be mainly constructed from ZnCr2O4 spinel grains, was porous in structure. Only the material containing 20% K2CrO4 (by weight) in ZnCr2O4 exhibited an exponential behaviour to humidity, which shows about three orders change in the dc resistance over the relative humidity (RH) range between 25 and 90%. The capacitive response to relative humidity with a threshold value of about 50% was also found to be more pronounced for this sample and a change in the magnitude of the impedance at 100 Hz, from 105 Ω at 10% RH to 103 Ω at 93% RH, at room temperature, is typical.