TiO₂/(K,Na)NbO₃ Nanocomposite for Boosting Humidity-Sensing Performances

Nanomaterials of TiO₂, (K_0.5Na_0.5)NbO₃, and the TiO₂/(K_0.5Na_0.5)NbO₃ nanocomposite were successfully synthesized by a hydrothermal method. Impedance-type humidity sensors were fabricated based on these materials. Our results reveal that the impedance of the TiO₂/(K_0.5Na_0.5)NbO₃ sensor changes by 5 orders of magnitude with an ultrahigh sensing response of S_f = 166 470 recorded at 100 Hz in the tested relative humidity (RH) range of 12-94%. This value is almost 2 and 4 orders of magnitude larger than that of the (K_0.5Na_0.5)NbO₃ and TiO₂ sensors, respectively. Interestingly, satisfactory response/recovery time (25/38 s, within 5 min), very small hysteresis (<5%), excellent stability, and good repeatability were also achieved in the TiO₂/(K_0.5Na_0.5)NbO₃ sensor. The improved sensing properties are ascribed to the synergistic effect of TiO₂/(K_0.5Na_0.5)NbO₃ heterojunction, which contributes the impedance that is susceptible to environmental humidity. This work underscores that it is a facile way to boost humidity-sensing performance by constructing proper nanocomposites.