Experimental Investigation on Moisture Sensing Behavior of La2O3 with La(OH)3 at Nanoscale

ABSTRACT This article reports the moisture-sensing behavior of a nanostructured La2O3 and La(OH)3. Pellets of this material were prepared and used as a sensing element after successive thermal annealing for 2 h at different temperatures of 200, 400, 600, and 800°C. After each annealing step, this sensing element was placed in a conductivity holder and exposed to humidity. Variations in resistance with relative humidity were recorded. The sensing material was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). A close look of the scanning electron micrographs confirms that the sensing element annealed at 400°C was more porous and uniform than the other samples. The maximum average sensitivity obtained was 19 MΩ/% relative humidity (RH) and results were found to be reproducible. The crystallite size of the sensing material was found to be in the range of 30–140 nm. The mass loss of the sensing material at different temperatures was also studied.