Characterization and Humidity Sensing Properties of the Sensor Based on Na2Ti3O7 Nanotubes

Na2Ti3O7 nanotubes was synthesized by a hydrothermal method, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Then the material was coated on Al2O3 ceramic substrate to fabricate humidity sensors using Ag–Pd as interdigitated electrodes. The sensor shows high humidity sensitivity and quick response-recovery time. The impedance changes about five orders of magnitude within humidity range from 11% to 95% relative humidity (RH). At the frequency of 100 Hz, the response time is 2 s and recovery time is 4 s, and the maximum hysteresis is less than 3% RH. Moreover, complex impedance property at different RH was investigated to study sensing mechanism. The results indicate the potential applications of Na2Ti3O7 nanotubes for fabricating high-performance humidity sensors.