An Al2O3 sensor for low humidity content: characterization by impedance spectroscopy

Sberveglieri, G.; Anchisini, R.; Murri, R.; Ercoli, Chiara; Pinto, Nicola

doi:10.1016/0925-4005(96)80100-6

Cited by 17 publications

(7 citation statements)

References 3 publications

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“…The humidity-sensing properties of alumina, discovered almost 50 years ago, [83][84][85][86][87][88][89][90][91][92][93][94] are based upon ionic conduction; the presence of an adsorbed layer of water at the surface reduces the total sensor impedance because of the increase in the ionic conductivity, as well as capacitance due to the high dielectric constant of water. The humiditysensing characteristics of a given sensing element depend upon the material used, the method of preparation, and the resulting surface topology.…”

Section: The Water Vapor Sensing Performance Of Highly Ordered Nanopomentioning

confidence: 99%

Metal Oxide Nanoarchitectures for Environmental Sensing

Varghese

Grimes²

2003

j nanosci nanotechnol

222

132

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Metal oxide materials are widely used for gas sensing. Capable of operating at elevated temperatures and in harsh environments, they are mechanically robust and relatively inexpensive and offer exquisite sensing capabilities, the performance of which is dependent upon the nanoscale morphology. In this paper we first review different routes for the fabrication of metal oxide nanoarchitectures useful to sensing applications, including mesoporous thin films, nanowires, and nanotubes. Two sensor test cases are then presented. The first case examines the use of highly uniform nanoporous Al2O3 for humidity sensing; we find that such materials can be successfully used as a wide-range humidity sensor. The second test case examines the use of TiO2 nanotubes for hydrogen sensing. Going from a nitrogen atmosphere to one containing 1000 ppm of hydrogen, at 290 degrees C, 22-nm-diameter titania nanotubes demonstrate a 10(4) change in measured resistance with no measurement hysteresis.

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Section: The Water Vapor Sensing Performance Of Highly Ordered Nanopomentioning

confidence: 99%

Metal Oxide Nanoarchitectures for Environmental Sensing

Varghese

Grimes²

2003

j nanosci nanotechnol

222

132

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“…Our interest is in developing reliable, high performance ceramic materials of large surface area for humidity and gas sensing. Therefore we have revisited the use of nanoporous alumina, a topic of considerable interest since the discovery of its moisture sensitive properties almost fifty years ago [21][22][23][24][25][26][27][28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Room Temperature Ammonia and Humidity Sensing Using Highly Ordered Nanoporous Alumina Films

Dickey

Varghese

Ong

et al. 2002

Sensors

130

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Abstract:The effect of pore size and uniformity on the response of nanoporous alumina, formed on aluminum thick films through an anodization process, to ammonia and humidity at room temperature is reported. Pore sizes examined range from 13 nm to 48 nm, with pore size standard deviations ranging from 2.6 nm to 7.8 nm. The response of the material to ammonia and humidity is a strong function of pore size and operating frequency. At 5 kHz an alumina sensor with an average pore size of 13.6 nm, standard deviation 2.6 nm, exhibits a factor of two change in impedance magnitude as it is cycled between an ammonia and argon environment. At 5 kHz the same sensor exhibits a well-behaved change in impedance magnitude of 10 3 over 20% to 90% relative humidity. Cole-Cole plots of the 5 Hz to 13 MHz measured impedance spectra, modeled using equivalent circuits, are used to resolve the effects of adsorption and ion migration.

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“…To obtain desired sensitivity for measuring humidity in trace level, the optimum pore size should be in the nanometer range [30]. The morphology of the nanostructure, electrode geometry and the dielectric constant of vapor molecules have a significant role in improving the characteristics of the sensor [31][32][33]. It has been noticed that as the sensing area of the sensor increases the sensitivity increases.…”

Section: Resultsmentioning

confidence: 98%