A humidity sensor based on KCl-doped nanoporous Ti0.9Sn0.1O2 thin films prepared by the sol–gel method

A humidity sensor based on KCl-doped nanoporous Ti0.9Sn0.1O2 has been developed by the sol–gel method and Pluronic P123 as the organic template on alumina substrates, and their humidity sensing properties have also been also investigated at different sintering temperatures. It is found that 50 mol% KCl doped nanoporous Ti0.9Sn0.1O2 thin film, sintered at 500 °C for 4 h, shows the best humidity sensing properties, and its impendence decreases more than four orders of magnitude from 109 Ω to 105 Ω with good linearity in the Relative Humidity (RH) range of 11%–95% at 25 °C. The response and recovery time of this sensor are about 11 and 14 s, respectively. High sensitivity, narrow hysteresis loop, rapid response and recovery, prominent stability and good repeatability are obtained. A possible mechanism is suggested to explain the humidity sensitive properties.