Humidity Sensitivity of Chemically Synthesized ZnAl2O4/Al

Humidity sensitivity is evaluated for chemically synthesized ZnAl2O4/Al devices. We succeeded
in synthesizing the ZnAl2O4/Al device by applying chemical techniques only. Hydrothermal
treatment for the anodized aluminum (AlOx/Al) gives us the device of the ZnAl2O4/Al structure.
All fabrication processes were conducted under 400 C. The key was focusing on ZnAl2O4 as the
sensing material instead of MgAl2O4, which is generally investigated as the humidity sensor. The
evaluation of this ZnAl2O4/Al device clarified its effectiveness as a sensor. Both electrical capacitance,
Cp, and the resistivity, Rp, measured by an LCR meter, obviously responded to the humidity with
good sensitivity and appreciable repeatability. Our synthesis technique is possible in principle to
improve on the process for the device with a complex structure providing a large surface area. These
characteristics are believed to expand the application study of spinel aluminate devices as the sensor.