Synthesis and characterization of nanocrystalline FexOy/Gd2O3/SiO2 composite powder

In this work, sol gel method was used to prepare FexOy/Gd2O3/SiO2 composite system starting from two different iron precursors: iron nitrate and iron oxide xerogel. The obtained samples were subjected to heat treatment at different temperatures under atmospheric conditions. Thermal evolution of the prepared samples has been systematically investigated by using X-ray diffraction (XRD) analysis and Fourier transform infrared spectroscopy (FTIR). Samples calcined at 1030 degrees C were also characterized by transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) experimental techniques. Effect of thermal treatment on phase formation in the prepared composite system has been discussed. It was found that iron nitrate based sample developed only alpha-Fe2O3 structural phase, while the sample based on the iron oxide xerogel developed alpha-Fe2O3 and gamma-Fe2O3 phases, with both of them remaining stable up to temperatures as high as 1030 degrees C. Gadolinium precursor crystallized directly in low-temperature triclinic B-type gadolinium disilicate Gd2Si2O7 (Gd2O3 center dot 2SiO(2)) phase at 900 degrees C, without formation of intermediate monosilicate phase. No other crystalline phases related to gadolinium were observed.