Humidity sensing properties of K0.5Na0.5NbO3 powder synthesized by metal organic decomposition

K0.5Na0.5NbO3 (KNN) powder is synthesized via a metal-organic decomposition (MOD) method and characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and energy dispersive spectrometer (EDS). A humidity sensor, which is consisted of five pairs of AgPd interdigitated electrodes and an Al2O3 ceramic substrate, is fabricated by spin-coating the KNN powder on the substrate. The humidity sensing properties of the KNN humidity sensor are investigated at room temperature within the relative humidity (RH) range of 11-95%. The variations of the KNN humidity sensor impedance are about four orders of magnitude within the whole humidity range from 11% to 95% RH at the frequencies of 60 Hz and 100 Hz. The response time and recovery time of the KNN humidity sensor are all about 8 s and 18 s, and their maximum hystereses are all around 2% RH at 60 Hz and 100 Hz. Furthermore, at low RH and frequency conditions, the dielectric dissipation factor (DF) values of the KNN humidity sensor are small and hardly change, indicating that the KNN humidity sensor is of good insulating properties and reliability. The KNN powder is of broader potential applications for fabricating high performance humidity sensors.