STUDY OF THE CONDUCTION MECHANISM OF MGAL2O4 AT DIFFERENT ENVIRONMENTAL HUMIDITIES

In this paper, the electrical properties of MgAl2O4, which has been proposed as a sensitive material for humidity detection devices, are discussed in relation to its microstructure. MgAl2O4 was studied both in bulk and in thin-film forms. Different pellets of MgAl2O4 were obtained by sintering powders prepared by different processes, in order to produce a different microstructure. 80 nm thick thin-films were prepared by radio-frequency sputtering on a Si/SiO2 substrate. Surface area, density and pore-size distribution were measured for the pellets. The microstructure of all the specimens was observed using SEM. The electrical behaviour of the specimens was studied using electrochemical impedance spectroscopy in the frequency range from 10(-2) to 10(5)Hz at relative humidity (RH) values ranging from 5 to 85%. The variation of dielectric parameters, calculated at different frequencies as a function of RH, was investigated to study the conduction mechanism. The humidity-sensitive electrical properties of MgAl2O4 were correlated with its microstructure. In order to determine the conduction carriers, the samples were polarized at 1 V dc and the charging and discharging currents were measured.