The influence of the heat treatment temperature in the magnetic characteristics of a SiO2-Li2O-Fe2O3 glass prepared by sol-gel

The glass with the molar composition 88SiO(2)-2Li(2)O-10Fe(2)O(3) (mole %) was prepared by the sol-gel route and after heat-treated at temperatures between 250 and 1000 degrees C under oxidizing conditions. Crystalline phases (LiFe5O8, SiO2, Fe2O3 and LiFe(Si2O6)) were observed by X-ray powder diffraction in the glasses treated at temperatures above 800 degrees C. Scanning electron micrographs reveal the presence of particles in the samples heat-treated up to 800 degrees C, which are essentially amorphous or with an incipient crystallization. The increase of the heat-treatment temperature promotes the coarsening of particles. The magnetic characteristics of the prepared glasses and glass ceramics were performed using a vibrating sample magnetometer in function of the magnetic field amplitude (-10 T <= B <= 10 T) and in function of temperature (5 K-300 K). The samples heat-treated at 900 and 1000 degrees C present a ferrimagnetic behavior accompanied by the appearance of peaks corresponding to the lithium ferrite phase (LiFe5O8). A curious aspect is the saturation magnetization of the sample heat-treated at 800 degrees C is the highest of all samples, indicating the highest amount of LiFe5O8 crystals. The Mossbauer results are in accordance with the magnetization and magnetic susceptibility measurements. (C) 2014 Elsevier B.V. All rights reserved.