Síntese de nanocristais de ferritas por rota solvotérmica

Abstract

In this study are presented cases on four ferrites (MFe2O4), the solvothermal method was chosen to synthesize the magnetic particles (ferrites) which has been standing out for allowing control over the size of the particles and for not permitting the formation of undesirable agglomerates in the material. The samples were characterized by x-ray diffraction (XRD), infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electrical characterizations performed with the thin films. The program MAUD (Material Analysis Using Diffraction) was used to evaluate the phases of the material and crystallite size of the ferrite samples. The materials presented grain size of 126 nm for CuFe2O4, 179 nm for CoFe2O4, 132 nm for ZnFe2O4 and 163 nm for NiFe2O4. Infrared spectroscopy was used to assess the ligand agent from Oleic acid, the results indicated the oleate group bound to the inorganic nanocrystals are responsible for stabilizing the colloidal solution and thus controlling the size of the nanoparticles. The TEM images confirm the size of the nanocrystals determined by xray diffractions, however the grains on the images did not present uniformity. The SEM images showed the surfaces of the thin films classified as homogeneous without evidence of cracks except to zinc ferrite. During the electrical characterization, all of the thin films presented Ohmic behavior on the measurements in the used bias and thermoresistance presents semiconductor behavior for the materials. The values of resistance, at temperature, around 573 K, was for the cobalt ferrite 919,7 kΩ, nickel 23,7 MΩ, copper 51,7 Kω and zinc 24,8 MΩ. The solvothermal method showed itself to be efficient in obtaining ferrite nanocrystals with crystallite size between 126 and 179 nm for syntheses of 48 hours.