Humidity Sensing Properties of CuO, ZnO and NiO Composites

The mixed metal oxides were investigated for humidity sensing properties. The composites were prepared by mixing 1:1 mole ratio of CuO-ZnO, CuO-NiO, and NiO-ZnO compound. The samples sintered at 800 oC for 5h, were subjected to do resistance measurements as a function of relative humidity (RH) in the range of 5-98 % and the sensitivity factor was calculated. Among the three composites, CuO-NiO compound possessed the highest humidity sensitivity of 2834.8 while the other two possessed a very low sensitivity factor. The response and recovery of the CuO-NiO composites were 650 and 80 s. X-ray diffraction, and scanning electron microscopy (SEM) was employed to identify the structural phases, and surface morphology of the metal oxide compounds

Humidity Sensing Characteristics of Bi2O3- added TiO2 Composites

The TiO2-Bi2O3 composites heated up to 700 °C for 5 h were characterized by X-ray diffraction, and scanning electron microscopy (SEM) and studied for humidity sensor. The composites were in the mole ratio of 98:2, 95:5, 90:10, 80:20 and 100:0 of TiO2 and Bi2O3 labeled as TOBO-1, TOBO-2, TOBO-3, TOBO-4, and TOBO-5, respectively. The samples sintered at 800 oC for 5h formed a new phase Bi2Ti4O11. The composites were subjected to DC resistance measurements as a function of relative humidity (RH) in the range of 5-98 % and the sensitivity factor was calculated from the relation Sf = R5%/R98% where R5% and R98% were the DC resistances of 5 % and 98 % RH respectively. Among the various composites, TOBO-3 composite possessed the highest humidity response with Sf = 2391.3, while the TOBO-5 and TOBO-2 composites possessed low sensitivity factors of 396.2 and 329.7 respectively. The response and recovery characteristics of the TOBO-3 composite were 420 and 150 s respectively