Microstructure and electrical properties of MgAl[sub 2]O[sub 4] thin films for humidity sensing

Journal Article · Mon Mar 01 00:00:00 EST 1993 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1993.tb03669.x· OSTI ID:6301516

Gusmano, G; Montesperelli, G; Traversa, E ^[1]; Mattogno, G ^[2]

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1. Univ. di Roma Tor Vergata, Rome (Italy). Dept. di Scienze e Tecnologie Chimiche
2. CNR, Rome (Italy). Inst. di Teroria e Struttura Electronica

Active elements for humidity sensors based upon MgAl[sub 2]O[sub 4] thin films or sintered pellets were investigated. Thin films were deposited on Si/SiO[sub 2] substrates by radiofrequency (rf) sputtering. Sintered MgAl[sub 2]O[sub 4] 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 MgAl[sub 2]O[sub 4]. Sintered MgAl[sub 2]O[sub 4] 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 40C in environments at different relative humidity (RH) values between 2% and 95%, using ac impedance spectroscopy. MgAl[sub 2]O[sub 4] 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 MgAl[sub 2]O[sub 4] pellets and thin films were correlated with their different microstructures.

• OSTI ID: 6301516
• Journal Information: Journal of the American Ceramic Society; (United States), Vol. 76:3; ISSN 0002-7820
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
ELECTRICAL PROPERTIES
MICROSTRUCTURE
MAGNESIUM OXIDES
COMPARATIVE EVALUATIONS
ELECTRIC CONDUCTIVITY
ELECTRIC IMPEDANCE
EXPERIMENTAL DATA
MOISTURE GAGES
PELLETS
PHOTOELECTRON SPECTROSCOPY
POROSITY
SAMPLE PREPARATION
SCANNING ELECTRON MICROSCOPY
SILICON
SILICON OXIDES
SINTERING
SPECTROSCOPY
SPUTTERING
STOICHIOMETRY
SUBSTRATES
THIN FILMS
X-RAY SPECTROSCOPY
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
DATA
ELECTRON MICROSCOPY
ELECTRON SPECTROSCOPY
ELEMENTS
EVALUATION
FABRICATION
FILMS
IMPEDANCE
INFORMATION
MAGNESIUM COMPOUNDS
MEASURING INSTRUMENTS
MICROSCOPY
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SEMIMETALS
SILICON COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360204 - Ceramics
Cermets
& Refractories- Physical Properties