Microstructure-dependent humidity sensitivity of porous MgFe2O4–CeO2 ceramic

In this paper cerium oxide is added to MgFe2O4 at concentrations of 2 wt%, 4 wt% and 6 wt% in the precursor, while preparing the samples by a ceramic method in our laboratory. All samples are highly resistive of the order of mega ohms at room temperature and humidity. The decrease in resistance has been observed from 52 MΩ to 2 MΩ for the addition of 6 wt% cerium oxide, obviously with increasing the relative humidity using a two pressure technique-based standard humidity generator. The relative humidity generated is in the range from 10% RH to 90% RH at 25 °C. The addition of cerium oxide in the spinel lattice increases the intergranular porosity, distribution of pore size and open pores. The porosity increases from 2.5% to 26%. With the addition of cerium oxide the sensitivity at low RH increases and shows a better linearity than that of pure magnesium ferrite. The d log R/d RH is measured for all cerium oxide added samples in a range of 40–60% RH range. The spinel phase present in the samples is confirmed by X-ray diffraction (XRD). The porosity is calculated by a porosity equation and confirmed by analyzing the scanning electron micrographs of the samples.