A capacitive-type humidity sensor using polymer electrolytes of PVA-LiCl thick films

Capacitive-type humidity sensors have been prepared using polymer electrolyte of poly (vinyl alcohol) (PVA) and lithium chloride (LiCl) thick films. Microstructure of the films were studied using XRD and SEM. SEM images of resultant polymer electrolytes thick films shown that the films are stacked by microparticles with particles size about 1 mm. The diffraction spectra confirmed that the LiCl forms nanocrystallites. Sensing characteristics and the sensing mechanism of the humidity sensors have been investigated by measuring the complex impedance of at different humidities and at various frequencies. The PVA-LiCl thick film RH sensors showed excellent humidity sensing properties over the wide relative humidity range from 33% to 94% RH. The sensitivity of the RH sensors depend on the operating frequencies and give the best sensitivity at 1 kHz.