Electrical and CO-sensing properties of NdFe1-xCoxO3 perovskite system

NdFe1-xCoxO3 (x=0.0-0.5) powders were prepared by a sol-gel citric method. X-ray diffraction was used to confirm the phase composition of the powders. All the samples are orthorhombic structure. The unit cell volume and grain size decreased with an increase of Co content x. The conduction type of the NdFe1-xCoxO3 perovskite oxides changed with the increasing Co content x. When x<0.3, the oxides showed p-type conduction behavior, and then changed to n-type when x>0.3. All the sensors presented higher responses and lower optimal operating temperatures. The highest response to 0.03% CO gas reached 1215% at 170 °C for NdFeO3 sensor; however, Co2+ doping in NdFeO3 did not improve the gas responses.