MICROSTRUCTURE AND ELECTRICAL-PROPERTIES OF MGAL2O4 AND MGFE2O4 SPINEL POROUS COMPACTS FOR USE IN HUMIDITY SENSORS

Among the various materials proposed in the relevant literature, porou s ceramic oxides possess suitable characteristics for use as active el ements in humidity sensors. Particular attention has been paid to the study of spinel-like oxides, which have also been used in prototype de vices, showing good humidity sensitivity in their electrical propertie s and fast response times. This paper discusses the performance of MgA l2O4 and MgFe2O4 spinels as sintered porous compacts in terms of their electrical response to relative humidity. The compacts were prepared by forming and sintering powders with different microstructures. The h umidity-sensitive electrical properties of the sintered compacts were correlated with their microstructural characteristics, which were dete rmined by means of scanning electron microscopy (SEM), mercury porosim etry, and specific surface area measurements, using the BET method wit h N2 as adsorbate.