Fast-Response Humidity Sensing Performance Based on LaFeO ₃ Perovskite

In this work, LaFeO 3 was synthesized via the sol–gel method and characterized to evaluate its potential for ultrafast humidity sensing applications. X-ray diffraction (XRD) confirmed the formation of a single-phase orthorhombic structure with a Pnma space group and high crystallinity. Scanning electron microscopy (FE-SEM) revealed a relatively homogeneous porous grain structure, while energy-dispersive X-ray spectroscopy (EDX) verified the presence of La, Fe, and O with stoichiometric weight percentages of 50.0%, 29.8%, and 20.2%, respectively. The sensing layer was deposited onto an interdigital transducer (IDT) with an Al 2 O 3 (alumina) substrate, and capacitance measurements using an LCR meter at 100 Hz were performed in the 11–96% relative humidity (RH) range at room temperature. The sensor exhibited a capacitance increase from 26.93 pF (11% RH) to 603.73 pF (96% RH), with a average hysteresis value of 6.2 %, response and recovery times of 9.7 s and 1.2 s, respectively, and a maximum sensitivity of 6.78 pF/%RH at 96% RH. These results indicate that LaFeO 3 is a promising candidate for the development of efficient, stable, and fast-response humidity sensors for practical applications in environmental monitoring and industrial process control.