HUMIDITY-SENSITIVE ELECTRICAL RESPONSE OF SINTERED MGFE2O4

Pellets of MgFe2O4 were prepared by sintering, at different temperatur es, powders prepared either by solid-state reaction between MgO and Fe 2O3, Or by the thermal decomposition of hydroxide mixtures, co-precipi tated from magnesium and iron nitrate solutions with an Mg/Fe ratio of 1 :2. Mercury porosimetry, specific surface area measurements and sca nning electron microscopy were used in order to determine the main mic rostructural characteristics of the pellets. Electrochemical impedance spectroscopy (EIS) was used to correlate the humidity-sensitive elect rical response of the pellets with their microstructure, in particular with total open porosity and pore-size distribution. EIS measurements showed a close correlation between their relative humidity dependence of the electrical resistance and the microstructure of the sintered b odies. Rather good reproducibility and a fast response time to humidit y variations, evaluated from d.c. measurements, were also observed. Th ese properties are also strictly dependent on the microstructure.