4. Conclusion
A novel nano composite material, Ni0.9Zn0.1O/ZnO, has been successfully obtained via the thermal decomposition of mixed precursor compound synthesized using a facile coprecipitation route and its gas sensing properties investigated for many gases (CO, H2 and NO2). According to the XRD results the nano composite materials were a homogeneous mixture of Ni0.9Zn0.1O and ZnO, excluding the possibility of the simple NiO/ZnO nano composite. Enhanced sensing properties with respect to CO were observed by comparison with those of pure Ni0.9Zn0.1O and ZnO structures and the optimal operating temperature was found to be 300◦C. It was also found that the as synthesized composite material can be used at lower operating temperature (225◦C) as selective NO2gas sensor. The humidity has no significant influence on the response of sensor beyond 20%. The heterojunction between Ni0.9Zn0.1O and ZnO and their catalytic activities are probably the principal factor responsible for the enhanced gas sensing performance of the composite material.