A capacitive-type NO2 gas sensor, developed by replacing metal in metal-insulator-semiconductor structure with solid electrolyte as sensing material, was investigated to improve the response and recovery rates and the operating temperature by modifying NaNO2-sensing material. Binary sensing materials of NaNO2-Ca3(PO4)2 and NaNO2-WO3 were tested for auxiliary phase of the device. The Ca3(PO4)2-containing phase showed a response closer to ideal Nernstian behavior at 140 °C as compared to WO3-containing phase. On the other hand, the WO3- containing phase showed faster response and recovery rates at 160 °C, while the response deviated from Nernstian correlation. In order to obtain optimum sensor response, a ternary phase of NaNO2-Ca3(PO 4)2-WO3 was used as sensing phase. The device with ternary auxiliary phase was found to show more stable and faster response and recovery rates at 130 °C, as compared to previous devices attached with binary phases, corresponding Nernstian correlation in the concentration range of 20-500 ppb NO2. Furthermore, the effects of modification process on the auxiliary phase were investigated through SEM observation of the surface structures and measurement of ionic conductivity.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Surfaces, Coatings and Films
- Metals and Alloys
- Electrical and Electronic Engineering
- Materials Chemistry