| There has long been interest in perovskite-structured compounds (of general formula ABO3) because of their unique catalytic action, colossal magnetoresistance effects and gas-sensing properties. The functional characteristic of ABO3-type with perovskite structure can be controlled by selecting suitable A and B atoms or chemical doping. Actuators based on ABO3-type oxide material of rare-earth elements were found to have a high sensitivity, a good selectivity and an excellent stability. Due to its potential use in gas sensor application, the gas-sensing materials based on perovskite -type oxide attracts much attention and becomes one of the most active topics in the field of functional materials. Among these materials, much attention was paid to LaFeO3.But the resistance of LaFeO3-based sensor is very high, which is a disadvantage in application, and with the shortcoming of its long response and recovery times. They may be modified when some part of the lanthanum in LaFeO3 is replaced by lower valent-cations, such as Ca, Sr and Ba. In this dissertation, the samples La(Pb)Fe(Co,Ni)O3 was prepared by the sol-gel citrate method. The structure, electrical and sensing properties were investigated. Following are summary of our works:1. The structure, electrical and sensing properties of La1-xPbxFeO3 (x≤0.3) samples(1) XRD patterns showed that La1-xPbxFeO3 (x≤0.3) samples were still perovskite phase with orthorhombic structure; With an increase of x value, the mean crystallite size reduces. It means that Pb-doping can restrain the growth of the grain size; Because Pb2+ ion is larger than the La3+, when the La3+ is replaced by the Pb2+ at the A-site, the unit cell volume should become larger with increasing x value. On the other hand, in the view of charge compensation, oxygen vacancies are produced to maintain a neutral charge. The lattice might be somewhat smaller in order to maintain normal perovskite structure. Therefore, when x = 0.2, the unit cell of the sample is...
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