Gas Sensing Measurements of a Novel NO₂ Sensor Using K₂CO₃/Al₂O₃ Composite Pellets From Resistive Aspect

K2CO3/Al2O3 composite pellets connected to gold contacts were employed as a resistive NO2 sensor. Gas sensing experiments showed that this structure has an acceptable response to NO2 at room temperature (RT) and its response increases drastically as the operating temperature decreases. It was found that highest gas–solid interactions occurred at
$\boldsymbol {T}$
= 10 °C with a sensor response of 44 in the presence of 900-ppb NO2. Evaluations of the response and recovery times of the sensor suggested that these parameters also significantly improved when sensor operates at RT. Typically, the response and recovery times to 900-ppb NO2 at RT (25 °C) were 65 and 473 s, respectively. NO2 detection limit is estimated to be 4 ppb at RT and 2 ppb at 10 °C. The linearity of the calibration curve in the NO2 concentration range between 40 and 1500 ppb combined with good selectivity, especially among alcoholic gases, makes this structure a good sub-ppm selective NO2 sensor at RT and cold body state.