Sol–gel processed TiO2–K2O–LiZnVO4 ceramic thin films as innovative humidity sensors

Active elements for humidity sensors based on TiO2–K2O–LiZnVO4 ceramic thin films have been prepared by the sol–gel technique. The films heated to 600°C, whose composition is Ti:K:Li:Zn:V:O=1:0.04:0.1:0.1:0.1:2.42 (molar ratios), are composed of semiconductor ceramics (rutile TiO2), alkali metal oxide (K2O) and glass (LiZnVO4). At the frequency of 40 Hz, the elementsʹ impedance (Zp), resistance (Rp) and capacitance (Cp) vs. relative humidity (rh) values all show variations higher than three orders of magnitude over the humidity range tested (10–99% rh), and the curves of Log(Zp)∼rh, Log(Rp)∼rh and Log(Cp)∼rh all show excellent linearity. The outstanding advantages of the elements are the great stability and pollutant resistance. The results also show small hysteresis, rapid responsibility, and satisfactory repeatability. The temperature and frequency affect the humidity sensitive properties obviously.