NASICON-based potentiometric CO₂ sensor combined with new materials operative at room temperature

The improvement for the deterioration of CO₂ sensing properties in lower humidity condition was attempted to a NASICON-based potentiometric CO₂ device operative at room temperature. To optimize the sensing electrode, the device was fabricated by using ITO powders with a large specific surface area and by using a mixture of ITO and basic oxide powders. Although CO₂ sensing properties of the device were markedly improved by applying the above ideas in lower humidity condition, it was confirmed that the basic EMF drifts with changing the humidity conditions. Further, to find out the appreciate reference electrode material, the thermal and chemical stabilities were examined by XRD measurement for three kinds of oxides such as Li _0.62CoO₂, Na_0.6CoO₂ and Li ₂TiO₃. As the results, Na_0.6CoO₂ and Li₂TiO₃ were much stabler than Li_0.62CoO ₂ thermally and chemically. It was also found that Li ₂TiO₃ has a poor electric conductivity. Therefore, Na _0.6CoO₂ is the most suitable material for the reference electrode of the NASICON-based device operative at room temperature.