Potentiometric CO(2) Sensor Using Li(+) Ion Conducting Li(3)PO(4) Thin Film Electrolyte

Li(+) ion conducting Li(3)PO(4) thin film electrolytes with thickness 300nm, 650nm and 1.2μm were deposited on Al(2)O(3) substrate at room temperature by thermal evaporation method. Reference and sensing electrodes were printed on Au interfaces by conventional screen printing technique. The overall dimension of the sensor was 3 × 3 mm and of electrodes were 1 × 1.5 mm each. The fabricated solid state potentiometric CO(2) sensors of type: CO(2), O(2), Au, Li(2)TiO(3)-TiO(2)| Li(3)PO(4) |Li(2)CO(3), Au, CO(2), O(2) have been investigated for CO(2) sensing properties. The electromotive force (emf) and Δemf/dec values of the sensors are dependent on the thickness of the electrolyte film. 1.2μm thickness deposited sensor has shown good sensing behavior than the sensors with less thickness. The Δemf values of the sensor are linearly increased up to 460°C operating temperature and became stable above 460°C. Between 460-500°C temperatures region the sensor has reached an equilibrium state and the experimentally obtained Δemf values are about 80% of the theoretically calculated values. A Nernst's slope of -61mV/decade has been obtained between 250 to 5000 ppm of CO(2) concentration at 500°C temperature. The sensor is suitable for ease of mass production in view of its miniaturization and cost effectiveness after some further improvement.