CO gas sensing properties of ZnO–CuO composite

In order to correct the reproducibility problem inherent in the hetero-contact gas sensor and to see the possibility of using the electrical composite material as a gas sensor, porous ZnO(n)–CuO(p) composite system was selected for the investigation. The electrical conductivity and CO gas sensing properties were examined between 70 and 530°C at a fixed relative humidity of 23%. ZnO–CuO samples containing pure CuO showed small gas sensitivity to 200 ppm CO, however those containing Al-doped CuO showed high sensitivity to the same gas near 200°C. The shape of the electrical conductivity curve was related to the gas sensitivity. The temperature showing maximum CO gas sensitivity decreased with the addition of CuO. These observations were explained by both the microstructure and the electrical properties of p/n contact of the composite.