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Preparation, Characterization, Magnetic and Electrical Properties of Double Perovskite Sr2FeMoO6

Author: ZhangZhang
Tutor: DiYongQing
School: Hebei University
Course: Inorganic Chemistry
Keywords: Magnetoresistance Double perovskite Sol - gel method . Microwave sintering Doping
CLC: O614
Type: Master's thesis
Year: 2010
Downloads: 51
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Abstract


Sol - gel method and microwave method successfully synthesized the double perovskite of magnetoresistance materials Sr2FeMoO6 and A Bit replace the series of compounds, and X-ray powder diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM ) phase structure, particle size, morphology and electromagnetic properties of the analysis and characterization of the synthetic product. First, the use of inexpensive activated carbon powder as a reducing agent using sol - gel method and successfully synthesized double perovskite Sr2FeMoO6 single phase to study the impact of synthetic samples of process conditions on the structure and magnetic properties of the product can determine the best process condition. Obtained the sample Sr2FeMoO6 case tetragonal lattice and has I4/mmm space group, unit cell parameters: a = 5.580?, C = 7.882?; Grain size less than 100nm; Curie temperature above room temperature, 1T magnetic field, the sample saturation magnetization at room temperature for 13.59A · m2/kg, room temperature magnetoresistance change was -10.02%; samples conductive mechanism belongs to a small polaron variable range hopping conduction mechanism. Then respectively replaced by Li, Na, K, Gd3 the Sr2 Sr2FeMoO6, sample structure and magnetic properties of A-site substitution. The results showed that: different contribution to the system due to doping ion induced spatial effects and electronic doping effects, Li, Na, K replace the lattice parameters of the samples presented a decreasing trend, while Gd replace the cell parameters of the sample than the undoped sample cell parameters; Li, Na, K replace the saturation magnetization of the sample are presented with the doping amount first increases and then decreases, with Gd3 substituted samples saturation magnetization The significant increase in the doping amount decreases. In to Sr1.9K0.1FeMoO6 example, the sol - gel method the synthesis Sr1.9K0.1FeMoO6 the reaction mechanism. Finally, explore a synthesis the double perovskite Sr2FeMoO6 new technology - microwave sintering method, with the traditional high-temperature solid-phase sintering method, and sol-gel method, compared with the synthetic short time, and energy efficient. The law of the samples remain tetragonal crystal system, space group I4/mmm, with unit cell parameters: a = 5.571?, C = 7.872? The electromagnetic properties that: microwave sintering method is conducive to improve the saturation magnetization of the sample and the magnetoresistance change rate 1T magnetic field, samples of the saturation magnetization at room temperature for 17.949A m2/kg room temperature magnetoresistance change rate of -15.63% of the samples were higher than the sol-gel method; belong to the adiabatic small polaron conduction mechanism of the conduction mechanisms. In addition, the combination of the results of XRD and infrared analysis, suggesting the reaction course: the microwave field, SrCO3, Fe2O3, MoO3 First reaction to generate precursors Sr2Fe2O5 and - prepared SrMoO4; precursor through activated carbon reduction, led to the formation of Fe-O-Mo bond thereby generate final product Sr2FeMoO6.

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Metal elements and their compounds
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