SYNTHESIS BY COMBUSTION REACTION AND CHARACTERIZATION OF IRONPEROVSKITES LaxBi1-xFeO3 (x = 0.00, 0.10, 0.20 and 0.30), APPLIED TO MULTIFERROICS
Perovskite, BiFeO3, multiferroic, dieletrics and distorted antiferromagnetism
The multiferroics in single phase of the perovskite BiFeO3 for LaxBi1-xFeO3 (x = 0.00, 0.10, 0.20 and 0.30) with the attributions BFO P.C., BFO700, BFO 830, L0.10BFO700, L0.20BFO700 and L0.30BFO700 were obtained by the method of adapted combustion reaction. The principal goal, this synthesis, is decrease the metastability of the BiFeO3 in doping with La3+ in temperatures of sintering of 700 and 830oC, influencing in their electrical and magnetic parameters. The materials formed were characterized by Rietveld refinement (DRX-Rietveld), Medium Infrared with Fourier transform (FTIR), Scanning Electron Microscopy with by Energy Dispersive Spectroscopy (SEM/EDS/ MAPPING), Thermal Analysis (TG/DTA) and Properties Magnetic and Electrical (VSM, ɛ’, ɛ’’ e tang δ). The preliminary results showed that the perovskite BiFeO3, (BFO single phase) sinterized in temperatures at 700 oC (BFO/ Rhombohedral /R3c) and 830 oC (BFO/ Triclinic /P1) were directly dependent of the termic parameters. The dopagens by La3+ in the samples BFO700, L0.10BFO700, L0.20BFO700 and L0.30BFO700 presented different values of saturation magnetization, which resulted in different symmetries and space groups being the Rhombohedral/R3c - 0,011314 µB/[f.u.], Orthorhombic/Pnma - 0,006516 µB/[f.u.], Orthorhombic/Pbnm - 0,011503 µB/[f.u.] and Orthorhombic/Pbnm - 0,009509 µB/[f.u.]), respectively. The analysis by FTIR/DRX-Rietveld showed the strong vibrations (530.34; 531.61; 551.51cm-1) attributed to octahedral stretch for perovskite (BiFeO3) that is a characteristic of the FeO6 geometries, related to distorted antiferromagnetic structures. The dielectricity of ceramics is greater than 6 and the tangent of losses smaller than -0.13 in range 0 – 0.5 GHz. The quality factor was measured and all were smaller than -10 the -25dB. These results of chemical substrates shows that the investigated ceramics can be applied to multiferroics antenna.