Preparation And Study On N Doped LaFeO₃ Perovskite Material

There has been a great deal of interest and studies in perovskite materials, due to their interesting electrical, magnetic and catalytic properties, and applications in colossal magnetoresistance, magnetocaloric effect and ferroelectricity. The researches mainly focus on two aspects: (1) cations doping in perovskite materials, (2) and creating oxygen vacancies. However, there are few researches on other nonmetal ions doping at oxygen site of perovskite materials. Oxygen ions constitute the octahedra which build the basic microstructure of perovskite materials. And the exchange mechanism involving 3d electrons of transition metal ions is via oxygen porbitals. Thus, it is essential to research oxygen ions replaced by other nonmetal ions in perovskite materials. In this paper, we research the effect of nitrogen ions doping on properties of perovskite material LaFeO₃. Some main results and innovations are listed as follows:1. The sol-gel method was used to prepare LaFeO₃ fine crystalline ceramic sample, which was sintered in gaseous environment of NH3, and the sample nitrogen ions doping in LaFeO₃ perovskite was obtained. It remains an orthorhombic perovskite structure with a space group Pnma. But nitride ions doping has increased its unit cell parameters to some extent and has an direct effect on the local environment of Fe ions in it.2. Further researches reveal that nitrogen ions doping in LaFeO₃ have changed its magnetism. LaFeO₃ is antiferromagnetic while the nitrogen ions doping sample shows an enhanced weak ferromagnetism. And the weak ferromagnetism is enhanced with the increase of nitrogen ions doping. The model of residual moment from a canted spin structure gives reasonable explanations to the enhanced weak ferromagnetism.