Development of Y3+ and Mg2+-doped zirconia thick film humidity sensors

Y3+-doped and Mg2+-doped zirconia thick film humidity sensors were investigated. The humidity sensors exhibited good sensing characteristics. The sensor got a high sensitivity with the impendence changed five orders of magnitude from 108 to 103 Ω in the relative humidity (RH) range of 11–98% at 20 °C. The response time is about 30 s for Y3+ doped sensor, and 5 s for Mg2+ doped one, and recovery time is 5 s for both sensors. Small humidity hysteresis is about 3% RH and 4% RH for Y3+ and Mg2+ doped ZrO2 sensors, respectively. Moreover, good repeatability, linearity and temperature properties of the both sensors were also exhibited. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and defect structure were used to analyze the influence of dopant on humidity sensitive properties. And the mechanism of humidity sensing properties was also discussed.