Synthesis And Characterization Of La-sr-fe-mn-o System And Pr-k-fe-mo-o System

In this paper, a series of perovskite La1-xSrxFe1-xMnxO3(0.3<x<0.7) and double perovskite PrKFexMo2-xO6(0.8≤x≤1.1) samples have been successfully synthesized by conventional reaction processing. By means of X-ray diffraction, vibrating sample magnetometer and electrical resistivity measurement, we investigated the crystal structure, magnetic and electric properties. The main works and results of the dissertation are as follow:1. Perovskite:X-ray diffraction pattern suggests that the crystal structure of all the series of perovskite La1-xSrxFe1-xMnxO3(0.3≤x≤0.7) samples belongs to orthorhombic structure with Pnma space group. The lattice parameter a, decreases firstly and following increase with Sr2+ and Mn4+ doped. The cell parameters b and c, decrease slightly with coupled substitution of Sr2+ for La3+ and Mn4+ for Fe3+. The magnetization of La1-xSrxFe1-xMnxO3 (0.3≤x≤0.7) samples decreases slowly with temperature. The magnetic transition temperatures of the samples are below 80.0 K. In the paramagnetic temperature range magnetic cluster is proposed and the sizes decrease with Mn4+ and Sr2+ doping up to 0.5, following magnetic cluster sizes increase sharply with continuing doping. The electrical behaviors of La1-xSrxFe1-xMnxO3 (0.3≤x≤0.7) samples demonstrate insulator and the electrical resistivity increases with Mn4+ and Sr2+ ions doped. The detailing analysis of electrical transport shows that the electrical process of some samples are controlled by variable range hopping model at low temperature and that the electrical transport of the others are described by two steps transport of small polaron model at low temperature and that electrical transport of all specimens is described by bipolaron model at high temperature.2. Double perovskite:The crystal structure of the samples PrKFexMo2-xO6(0.8≤x≤1.1) presented monoclinic system. The space group of samples is P21. The lattice parameter decreases with the x increaseing. The magnetization of the series of PrKFexMo2-xO6(0.8≤x≤1.1) decreased with the magnetic field and decreased with the temperature. The samples were antiferromagnetic and the transition temperature was not observed in the studied temperature range. It means the curie temperature is below 80K.