Improvement of humidity sensing performance of BiFeO3 nanoparticles-based sensor by the addition of carbon fibers

Abstract This paper presents humidity sensing elements based on bismuth ferrite nanoparticles BiFeO3 (BFO) synthesized by a sol-gel method and bismuth ferrite / carbon fibers nanocomposites (BFO/CFs) prepared by a hydrothermal process. The morphological and structural characteristics of the nanomaterials were realized by SEM, BET, XRD, and Raman spectroscopy. The electrical properties of the sensing elements were studied by impedance spectroscopy. The humidity sensing properties of the two elements (BFO and BFO/CFs) were studied in the frequency range 300Hz-1 MHz, at room temperature and over the relative humidity (RH) range between 16 and 92 %. The results showed that the impedance of the developed sensors decreases considerably when the sensitive layers absorb water vapor. We also noticed that they have a small hysteresis and good stability. Compared to the BFO-based humidity sensor, the BFO/CFs based humidity sensor shows a high sensitivity of 12640 %. Finally, in order to understand the mechanisms of adsorption of water molecules on the surface of the sensitive layers, we plotted the variation of the imaginary part of the impedance versus the real part. The results showed that the relaxation mechanism is predominant. The results presented in this paper demonstrate the potential of BFO/CFs composite in the design of high-performance humidity sensors.