Preparation And Characterization Of Double Perovskite La-K-Fe-Mo-O System

In this paper, double perovskite LaKFeMoO₆,LaKFe_1-xNi_xMoO₆ (x=0.05, 0.1, 0.15) and LaKFeMoO_6-xS_x (x=0.1, 0.3, 0.5, 0.7, 1) samples have been successfully synthesized by conventional reaction processing. By means of X-ray diffraction meter, vibrating sample magnetometer and four-point probes method, the crystal structure, magnetic and electric properties have been investigated. The main results of this work are shown as follows:The structure of the double perovskite LaKFeMoO₆ sample belongs to monoclinic system with space group P21/n. X-ray diffraction pattern suggests that the lattice parameters are a= 5.5782A, b= 5.5981A, c= 7.8866A,β= 89.9542°, and V= 246.277A3. Thermal magnetization shows that the magnetization decreases slowly with temperature, and the transition temperature was not observed in the studied temperature range (80-300K) which indicated that the transition temperature is over 300K. The magnetic moment in the FC mode is higher than that in the ZFC mode. The electrical behavers of the samples belongs to the characteristic of the semi-conductor properties, the electrical transport can be described by polaron of non-adiabatic model.The structures of the series of double perovskite LaKFe_1-xNi_xMoO₆(x=0.05, 0.1, 0.15) samples belong to monoclinic system with space group P21/n. The lattice volumes decrease with the content of Ni increasing. Thermal magnetization shows that the magnetization decreases slowly with temperature, and the transition temperature was not observed in the studied temperature range (80-300K) which indicated that the transition temperature is over 300K. The magnetic moment increases gradually with the increase of magnetic field, and the magnetic moments increase with the content of Ni increasing.The structures of the series of double perovskite LaKFeMoO_6-xS_x (x=0.1, 0.3, 0.5, 0.7, 1) samples belong to monoclinic system with space group P21/n. The lattice volumes increase with the content of S increasing. Thermal magnetization shows that the magnetization decreases slowly with temperature, and the transition temperature was not observed in the studied temperature range (80-300K) which indicated that the transition temperature is over 300K. The magnetic moment increases with the increase gradually of magnetic field; The magnetic moment first increase and then decrease with the content of S increasing, it is max when x=0.5. The electrical behavers of the samples belong to the characteristic of the semi-conductor. The samples show distinct magnetoresistance effects. The electrical transportation of LaKFeMoO_6-xS_x (x=0.1, 0.3, 0.7, 1) can be described by homing activation model, while that of LaKFeMoO_6-xS_x (x=0.5) can be described by variable range hopping of small polaron model.