Effect of Piezoelectric Vibration on the Humidity Sensing Behavior of Nanoporous Alumina
Date Issued
2012
Date
2012
Author(s)
Huang, Po-Cheng
Abstract
Nanoporous anodic aluminum oxide (AAO) has attracted great attention due to its potential application in humidity sensing. The effect of raising temperature on the adsorbed water layer at AAO surface was widely studied. In this study, the effect and mechanism of piezoelectric vibration on the adsorbed water layer at the AAO surface, which were not reported before, has been investigated by impedance spectroscopy (IS) and capacitance measurement. This is achieved by building a composite structure consisting of an AAO layer and a piezoelectric ceramic layer.
At high relative humidity (RH) values, due to the large amount of water covered on AAO surface, the piezoelectric vibration only disturbs the conduction in low measuring frequencies. In contrast, at low RH values, the piezoelectric vibration mainly repels part of the adsorbed water layer at the AAO surface, producing an impedance curve similar to that of a lower RH under no piezoelectric vibration.
AAO humidity sensor exhibits a good sensing sensitivity at low measuring frequencies. When the piezoelectric vibration is applied, the sensitivity at low RH values sharply increases, but the linearity is lost. Under a long period of piezoelectric vibration, the AAO surface experiences a fatigue phenomenon, an issue that needs to be considered during its application.
Subjects
Anodic aluminum oxide (AAO)
Humidity sensing
Piezoelectric vibration
Impedance spectroscopy
Dielectric properties
Equivalent circuit.
Type
thesis
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