GAS-SENSING INTERFACES OF SOLID-ELECTROLYTE BASED CARBON-DIOXIDE SENSORS ATTACHED WITH METAL CARBONATE

The solid electrolyte CO2 sensor which has combined a NASICON based el ectrochemical cell with a metal carbonate auxiliary phase is shown to have two gas-sensitive interfaces, i.e., NASICON/sensing electrode (O- 2-sensitive) and carbonate/ sensing electrode (CO2-sensitive). The lat ter interface dominates the EMF of the device in the high temperature region, providing the device with CO2 sensing capability. In the lower temperature region, on the other hand, the former interface becomes d ominant, resulting in a complete loss of CO2 sensitivity. The use of a binary carbonate auxiliary phase can effectively extend the lower lim iting temperature of CO2 sensing.