Mixed-potential-type NO2 sensor using stabilized zirconia and Cr2O3–WO3 nanocomposites

A series of mixed W/Cr oxides with different ratio of W and Cr (1:6, 1:2 and 3:2) have been prepared by using polymeric precursor method. By comparing their sensitivities to 20–300 ppm NO2, it was found that the sensor using oxide with 3:2 W/Cr gave the largest response value. For 3:2 W/Cr oxide, the effect of the sintering temperature on the electrode microstructure was also investigated. As a result, the device sintered at 1000 °C showed the best performance. The response value to 100 ppm NO2 is 51.6 mV, the response time is within 20 s and the sensing device also shows an excellent selectivity against other coexisting gases. The characteristics of SEM and TEM revealed that the special microstructure of oxide electrode formed by sintering plays a significant role in better sensing performance.