Characterization and humidity sensing properties of Bi0.5Na0.5TiO3–Bi0.5K0.5TiO3 powder synthesized by metal-organic decomposition

Bi0.5Na0.5TiO3–Bi0.5K0.5TiO3 (BNT–BKT) powder is synthesized by a metal-organic decomposition method and characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). A humidity sensor, which is consisted of five pairs of Ag–Pd interdigitated electrodes and an Al2O3 ceramic substrate, is fabricated by spin-coating the BNT–BKT powder on the substrate. Good humidity sensing properties such as high response value, short response and recovery times, and small hysteresis are observed in the sensing measurement. The impedance changes more than four orders of magnitude within the whole humidity range from 11% to 95% relative humidity (RH) at 100 Hz. The response time and recovery time are about 20 and 60 s, respectively. The maximum hysteresis is around 4% RH. The results indicate that BNT–BKT powder is of potential applications for fabricating high performance humidity sensors.