In this work, we have succeeded in synthesizing monoclinic and hexagonal La₂O₂CO₃ using two different routes and revealed that both of them are sensitive to CO₂ to the same degree. Moreover, we observed that the resistance of the sensor based on hexagonal phase is much higher and more stable than the one of the sensors based on the monoclinic phase. Using Operando and time resolved XRD measurements, we have also demonstrated that the resistivity of the sensor based on monoclinic La₂O₂CO₃ increases because of the material transformation into the hexagonal phase during an exemplarily aging process.

Rare-earth oxycarbonates have been proposed as promising chemoresistive materials for CO₂ sensors. In this contribution we present the results of a broad investigation focused on selecting the best candidates in the rare-earth compounds and, in the case of the best performing material, preliminary results dealing with the understanding of sensing by the operando methods.