Pulsed laser annealing of sodium super ionic conductor for carbon dioxide sensors

This paper discussed a way to improve solid electrolyte carbon dioxide (CO₂) sensor by excimer laser annealing of sodium super ionic conductors (NASICON). The CO₂ sensor used in this paper consists of a thin NASICON layer. We additionally annealed the NASICON to improve its electrical conductivity by pulsed excimer laser. The laser annealing results in re-crystallization of the NASICON thin film and changes the conductivity, grain sizes, and the structure of grain boundaries. From the scanning electron microscope pictures, we saw that NASICON grain sizes were enlarged after laser annealing. Grain sizes were also correlated to laser annealing energy and annealing times. After 2 times annealing of 420 mJ laser energy with 7 pulses each time at 1 Hz repetition rate, the conductivity of NASICON was increased by 90%. When the CO₂ concentration was changed from 1000 ppm to 5000 ppm, the sensor resolution was enhanced up to 66%. These results suggested that appropriate laser annealing treatment not only enlarges NASICON grain sizes but also reduces its resistance. Therefore, the NASICON CO₂ sensor resolution can be improved accordingly.