Crystal Structure And Property Of Double Perovskites Sr_2-xA_xCoSbO₆ (A=La, K) And Sr₂Co_1-xFe_xSbO₆ Metal Oxides Systems

In this paper, double perovskite compound samples Sr2-xAxCoSbO6 (A = La, K) and Sr2Co1-xFexSbO6 (0.0≤x≤1.0) have been prepared by conventional solid-state reaction processing. The crystal structure has been characterized by X-ray powder diffraction (XRD) and infrared radiation (IR) spectroscopy, the magnetic and electrical properties have been studied by Alternating Gradient Magnetometer (AGM) and four-point probe method, respectively, the main results of the dissertation are as follows:For the compound Sr2CoSbO6, the Rietveld refinement of the structure was performed using the Fullprof program by XRD data. The result shows that it has a monoclinic system with the space group P21/n, and no impurity phase exists in the sample. There is a partial ordering (80%) of the Co3+ and Sb5+ cations over the B positions; The infrared spectra show typical of double perovskite oxide; The sample shows paramagnetic at room temperature, and the effective magnetic moment is 3.929μB. The thermal magnetization (M-T) curve shows that the magnetic phase transition temperature TN is about 50K; Sample Sr2CoSbO6 exhibits semiconductor behavior between 300 and 473K. The electrical transportation can be described by the small polaron variable-range hopping model.For the series of samples Sr2Co1-xFexSbO6 (0.1≤x≤1.0), the structure is monoclinic with the space group P21/n, and they are all single-phase. The unit cell volume increases and then decreases with the addition of Fe; The infrared spectra show typical of double perovskite oxides; The compounds show paramagnetic at room temperature, and the effective magnetic moment increases with the doping amount x increasing; The samples exhibit semiconductor behavior, and resistivity increases with the addition of Fe; The conductive mechanism of the samples belongs to the small polaron variable-range hopping model.For the series of samples Sr2-xKxCoSbO6 (0.1≤x≤0.5), the structure is monoclinic with the space group P21/n, and they are all single-phase. The unit cell volume decreases and then increases with the addition of K; The infrared spectra show typical of double perovskite oxides; The compounds show paramagnetic at room temperature, and the effective magnetic moment increases with the doping amount x increasing; The samples exhibit semiconductor behavior, and resistivity increases with the addition of K; The electrical transportation of the samples of x = 0.1, 0.3, 0.5 can be described by the small polaron variable-range hopping model, that of x = 0.2, 0.4 belongs to the adiabatic small polaron hopping model.For the series of samples Sr2-xLaxCoSbO6 (0.5≤x≤1.0), the structure is monoclinic with the space group P21/n, and they are all single-phase. The unit cell volume increases with the doping amount x increasing; The infrared spectra show typical of double perovskite oxides; The samples show paramagnetic at room temperature, and the effective magnetic moment increases with the addition of La; The samples exhibit semiconductor behavior, and resistivity increases with the addition of La; The conductive mechanism of the samples can be described as the small polaron variable-range hopping model.