Static characteristic of planar-type CO2 sensor based on NASICON and with an inner-heater

The structure and the static characteristic of planar-type solid electrolyte CO2 sensor are introduced. It was fabricated by the combination of carbonate auxiliary phase with a NASICON chip (2.5 x 0.5 mm), while a passage of Pt wire coiled into suitable form acting as inner-heater was pressed into the chip. When being measured in static state, it exhibited stable EMF response to 100-2000 ppm CO2 in air over a current range of 200-300 mA, and its characteristic was almost independent of partial pressure of O-2. The 90% response time were less than 10 and 50 s, respectively when the heating current was kept at 270 mA. Furthermore, the difference in characteristic due to different carbonate auxiliary phase and its sensing mechanism are also preliminary investigated. (C) 1997 Elsevier Science S.A. All rights reserved.