STUDY OF THE CONDUCTION MECHANISM OF MGAL2O4 AT DIFFERENT ENVIRONMENTAL HUMIDITIES

In this paper, the electrical properties of MgAl2O4, which has been pr oposed as a sensitive material for humidity detection devices, are dis cussed in relation to its microstructure. MgAl2O4 was studied both in bulk and in thin-film forms. Different pellets of MgAl2O4 were obtaine d by sintering powders prepared by different processes, in order to pr oduce a different microstructure. 80 nm thick thin-films were prepared by radio-frequency sputtering on a Si/SiO2 substrate. Surface area, d ensity and pore-size distribution were measured for the pellets. The m icrostructure of all the specimens was observed using SEM. The electri cal behaviour of the specimens was studied using electrochemical imped ance spectroscopy in the frequency range from 10(-2) to 10(5)Hz at rel ative humidity (RH) values ranging from 5 to 85%. The variation of die lectric parameters, calculated at different frequencies as a function of RH, was investigated to study the conduction mechanism. The humidit y-sensitive electrical properties of MgAl2O4 were correlated with its microstructure. In order to determine the conduction carriers, the sam ples were polarized at 1 V dc and the charging and discharging current s were measured.