SYNTHESIS AND CHARACTERIZATION OF Co 3 O 4 POWDERS FOR HUMIDITY SENSING

In last few decades, great deal of research efforts were directed towards the development of miniaturized gas-sensing devices, particularly for toxic gas detection and for pollution monitoring. Though various techniques are available for gas detection, solid state metal oxides offer wide spectrum of materials with their high sensitivities for the detection of different gaseous species. In this paper, we report the humidity sensing behavior of cobalt oxide ( Co 3 O 4 ) pellets. The Co 3 O 4 powder was prepared from the precipitation of CoSO 4 using NaOH solution. This as-prepared powder was heated at 600 °C for 2hr. The as-prepared powder was characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The humidity sensing behavior of Co 3 O 4 pellets (wt. ~ 0.5 gm, diameter ~ 10 mm) was noted by using home-built static gas sensing system. The characterization studies showed the high material purity and single phase Co 3 O 4 with cubic spinel symmetry in the as-prepared particles of resultant powders. The humidity sensing characteristics of Co 3 O 4 pellets were found to be good. The recovery time (~ 20 sec) was found to be small as compared to its response time (~ 60 sec).