Humidity sensor applications based on mesopores LaCoO3

Abstract

Humidity sensor plays a pivotal role in determining the quality of products and the precision of instruments. In order to measure and control humidity, LaCoO3 mesopores sensor was prepared by a modified citrate technique. The sample was characterized by X-ray diffraction, Field emission scanning electron microscopy, High resolution transmission electron micrographs, Energy dispersive X-ray spectroscopy and Brunauer–Emmet–Teller. LaCoO3 exhibits rhombohedral distorted perovskite crystal structure with R3c space group. The humidity-sensing properties were investigated in a wide range of working humidity (11–97% RH) and frequency (100 Hz–100 kHz). The obtained results confirm that the optimum measuring frequency is 1 kHz. A great advantage of LaCoO3 is its porosity, which is essential for a humidity sensor. These pores serve as humidity adsorption sites. Another advantage is its high resistivity, which is reduced by approximately eight times its normal magnitude with increasing the surrounding humidity. The average crystallite size and surface area of the sample are 12.88 nm and 154.125 m2/g respectively. According to VSM results, the hysteresis loop of the sample indicates its paramagnetic nature. Furthermore, the ferroelectric hysteresis loop, that was observed at room temperature, implies the antiferroelectric nature of LaCoO3 nanoparticles. The obtained data confirms that the LaCoO3 sample is very sensitive to humidity and can be commercially used as a humidity sensing element.