Nanostructured Cu/Zn/Al-based oxide as a new sensing material for NO2 detection

The gas sensing properties of a ternary mixed-metal oxide (CuO/ZnO/Al2O3, CZA) are here reported. The CZA-based powder was prepared by co-precipitation synthesis technique. Then, the sensing material was screen-printed onto alumina substrates with interdigitated platinum electrodes and calcined at 350 °C for 1 h. The sensors were first tested under 25 ppm NO2 at different temperatures, ranging between 24 up to 200 °C. The best compromise between the sensor response and the recovery times was achieved at 100 °C. Then, the investigated concentration range was varied from 250 ppb up to 25 ppm and a maximum response of about 95 % was measured under 25 ppm of the target gas. Response times were reasonably fast while, on the contrary, recovery times were quite long. In addition, the CZA sensor was also able to detect from 3 up to 300 ppm of NH3 at a working temperature of 200 °C. Interferences were also studied with NO2-humid air and in the presence of CO2-dried gas.