NASICON based CO2 gas sensor with an auxiliary electrode composed of LiCO3-metal oxide mixtures

Stability of CO2 sensing performance was strongly influenced by additives to the auxiliary electrode layer for the sensor with CO2,Pt/Li2CO3/Na3Zr2Si2PO12/Pt structure. Use of a mixture of Li2CO3 with some metal oxide was effective to stabilize the response behavior, and a stable response was achieved in a shorter period for the as-prepared sensor. It is proposed that a layer composed of the oxide particles covered with carbonates acts as a stable diffusion boundary layer to separate an auxiliary electrode and the NASICON phase. The formation of the metal oxide covered with carbonate was also effective to increase the activity in the auxiliary electrode phase. The increase in the activity is contributed to the balance of the chemical potential and the electrostatic forces for the ions in the diffusion boundary layer. (c) 2006 Elsevier B.V. All rights reserved.