EPR studies of some thick film ferrates, aluminates and their correlation with humidity sensitivity

Ceramic types of humidity sensors using aluminates and ferrates have attracted attention of workers as stable sensors. It is expected that there are some active centers on the surface of the sensors which are responsible to break the water vapor molecule in to H3O+ and OH− ions. These active centers can be unpaired spins or dangling bonds which can be measured using electron paramagnetic resonance (EPR). In the present paper, the dangling bond density of various samples of magnesium aluminates, magnesium ferrates and their mixtures prepared at different temperatures is monitored and correlated with the sensitivity of the humidity sensor prepared. It is found that the sensitivity is increasing as the dangling bond density increases.