Gas sensing properties of ZnFe2O4/ZnO screen-printed thick films

This paper investigates the use of iron and zinc oxide thick film materials, screen-printed onto glass substrates with silver electrodes. The sensor was interfaced with three resistors to form a bridge circuit. This was then used to detect methanol, ethanol and propanol vapours within a concentration range of 0-3000 ppm. The sensitivity of the sensor is defined as the change in bridge output voltage (mV) per change in gas concentration (ppm). The sensitivity of the sensor to 3000 ppm methanol, ethanol and propanol at room temperature was 3.5, 6.6, 22 μV/ppm while the relative resistance change of the sensor was calculated as (ΔR/R) × 100 and was 0.84, 2.5 and 5.2, respectively. The device exhibited the highest sensitivity to propanol, followed by ethanol and methanol, respectively. The recorded sensitivity decreased when the temperature was increased from room temperature 25 to 65 °C. The response/recovery times of the sensor to 1000 ppm propanol were seen to improve with increased temperature, being 45/90 s at 25  °C and 22.5/45 s at 65 °C.