A Comparative Study on the Moisture Response of Nanoporous γ-Alumina with Parallel Plate and Micro-Interdigital Electrodes
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Nanoporous γ-alumina thick films were prepared from its aqueous sol which in turn was prepared from an organometallic precursor. Ethylacetoacetate was added into the sol as a crack suppressing agent. The sensing behavior of the said film was measured in capacitive mode both in percentage relative humidity (%RH) level as well as parts per million by volume (ppmv) level moisture present in the gas phase. Two different electrode designs viz. parallel plate [parallel electrode configuration (PEC)] and micro-interdigital (inter-digital configuration) were employed for the sensing study. PEC shows superior sensing behavior over the interdigital electrode. The capacitance of the sensor with PE and ID configuration increase from ∼ 17 pF to ∼ 153 pF and ∼ 15 pF to ∼ 24 pF, respectively, as the moisture content increased from 2 ppm to 100 ppm. Further, the capacitance of the sensor with PE and ID configuration increased from ∼ 151 pF to ∼ 963 pF and ∼ 97 pF to ∼ 521 pF, respectively, as moisture content increased from 5% to 60%RH. Schematic and equivalent circuit diagrams for both electrode designs were invoked to explain the achieved superior sensitivity. In addition, the fabricated γ-alumina thick film based capacitive moisture sensor in parallel plate electrode geometry demonstrates low hysteresis (∼ 10 pF at 60%RH and ∼ 0.8 pF at 50 ppmv moisture content), appreciable repeatability over 15 cycles, prolonged stability for 12 months, robustness, drift-free measurement, impressive resolution, usability at high temperature, magnetic field, radiative and corrosive/toxic gas environment.
KeywordsNanoporous γ-alumina interdigital electrode parallel plate electrode thick films capacitive moisture sensor
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The authors are thankful to (DST–SERB, Sanction Letter No. EEQ/2016/000190, GAP 0361) for financial support. The authors are also thankful to the director of the CSIR-Central Glass and Ceramic Research Institute, Kolkata, for rendering all sorts of cooperation for conducting the research work.
Conflict of interest
The authors declare that they have no conflict of interest.
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