Active elements for humidity sensors based upon MgAl2O4 thin films or sintered pellets were investigated. Thin films were deposited on Si/SiO2 substrates by radiofrequency (rf) sputtering. Sintered MgAl2O4 pellets were prepared by traditional ceramic processing. Scanning electron microscopy (SEM) analysis showed that the thin films were rather dense and homogeneous, made up of clustered particles of about 20–30 nm, while the pellets showed a wide pore‐size distribution. X‐ray photoelectron spectroscopy (XPS) demonstrated that the thin films have a stoichiometry close to that of MgAl2O4. Sintered MgAl2O4 is crystalline, while it is disordered in thin‐film form. The presence of two different components of the Al 2p peaks was correlated with the structural difference between pellets and thin films. The relationship between good film–substrate adhesive properties and the chemical composition at the interface was studied. The electrical properties of the sensing elements were studied at 40°C in environments at different relative humidity (RH) values between 2% and 95%, using ac impedance spectroscopy. MgAl2O4 thin films showed interesting characteristics in terms of their use in humidity‐measurement devices. Resistance versus RH sensitivity values showed variations as high as 4 orders of magnitude in the RH range tested for thin films, and 5 orders of magnitude for pellets. The differences in the electrical behavior of MgAl2O4 pellets and thin films were correlated with their different microstructures.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of the American Ceramic Society|
|State||Published - Jan 1 1993|
ASJC Scopus subject areas
- Ceramics and Composites
- Materials Chemistry