Powders of BaSnO3 were synthesized to obtain gas sensor thick films (using the screen printing technique) for the detection of O2 and CO. Impedance spectroscopy was used at different atmospheres and temperatures. In the presence of O2, the films showed a maximum value of sensitivity at 300 °C, with the powders formed by Pechini presenting greater reproducibility and sensitivity (with an order of magnitude greater than that for the powders formed by precipitation). Results showed that the films formed with powders obtained using the Pechini method presented a better response to CO, with a maximum sensitivity at 450 °C. In addition, in the presence of CO and for T > 250 °C, these films showed an anomalous behavior regarding their sensitivity as a function of time when platinum electrodes were used: a great increase in the electrical resistance value for exposure times greater than 10 min.
