Influence of Grinding and Pressing of the Powder 50.0 wt% Fe, 47.0 wt% BaTiO3 and 3.0 wt% TiO2 on Morphology, Microstructure and Magnetic Properties

Abstract

Mixing the powders Fe (50.0 wt%), BaTiO3 (47.0 wt%) and TiO2 (3.0wt%) provides a mixture consisting of a matrix of smaller particles BaTiO3 in which larger particles Fe and TiO2 were embedded. The powder grinding results in the crystal grains cracking, increase in both dislocations and internal microstrains, aggregates formation, decrease in the content of crystalline phases due to formation of amorphous and oxidation of Fe in its oxides. Crushing of Fe crystalline grains with increasing grinding time up to 110 min causes an increase in magnetization. With further increase in the grinding time up to 170 min, the magnetization decreases due to lowering of the Fe content, resulting from FeO formation. From 170 min to 220 min, the oxidation of FeO to Fe3O4 and Fe2O3 causes an increase in the magnetization. Annealing the pressed sample ground for 110 minutes from 270 to 400°C results in the structural relaxation and thus, the increase in magnetization of the cooled sample. In the temperature range of 400 to 620°C, by increasing the annealing temperature up to 440°C the magnetization of the cooled sample increases, reaches its maximum and hereafter decreases. This magnetization change is mainly due to sudden increase in the size of Fe crystal grains and oxidation of Fe to FeO.