NASICON-based Electrolyte Carbon Dioxide Sensor for Monitoring Air Quality inside Automobiles

In this paper, we report how to improve the performance of a solid-state carbon dioxide (CO₂) gas sensor based on NASICON solid electrolyte (Na₂Zr₂Si₂P₃O₁₂) with a Li₂CO₃ auxiliary layer. The sensor is fabricated by micromachining processes and the die size is 3.2mm × 4.5 mm. Both potentiometric and amperometric sensing methods for detecting the CO₂ concentration are discussed. It shows clearly that amperometric driving method is more suitable to be adopted in automobiles due to good linearity. In addition, the experimental results demonstrate that the sensing resolution of NASICON electrolyte can be improved by KrF (Krypton-Fluoride) excimer laser annealing because grain sizes of sensing chemicals are more uniform after annealing.