Highly sensitive humidity sensor based on high surface area mesoporous LaFeO3 prepared by a nanocasting route

Mesoporous LaFeO3 with high surface area and pore volume was prepared through a nanocasting route by using mesoporous silica SBA-15 as a hard template. The structure and chemical composition of the sample were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS). The humidity sensing properties of the mesoporous LaFeO3 were investigated. Impedance greatly changes by more than five orders magnitude (1.7 × 106 to 4.5 kΩ) when the relative humidity varies from 11% to 98% at 10 Hz, and it also exhibits the satisfactory response time, hysteresis and stability. The sensor utilizing mesoporous LaFeO3 via nanocasting method displays superior humidity performance compared to that using bulk LaFeO3 via sol–gel technique. Such sensing behavior of the mesoporous LaFeO3 can be attributed to the high surface area (83.2 m2/g) and porosity, which lead to highly effective interaction between the water molecules and the surface active sites. A possible mechanism is discussed to explain the excellent performance of the humidity sensing device using the mesoporous LaFeO3.