Influence of mechanical activation on functional properties of barium hexaferrite ceramics

Abstract

Barium hexaferrite ceramics were prepared using mechanically activated mixtures of iron and barium titanate. The 60:40 mass% Fe:BaTiO 3 powder mixtures were mechanically activated for different times (100-240 min) and sintered at 1100 and 1200 o C in order to determine the influence of mechanical activation of the precursor on the magnetic and dielectric properties of the resulting barium hexaferrite ceramics. The final product contained 84-89 mass% of Ba 2 Fe 22.46 O 38 Ti 1.54 phase, with higher content corresponding to longer mechanical activation of the precursor. XRD and Raman measurements indicated that the remainder of the sample consists of leftover BaTiO 3 and hematite, which was formed by the oxidation of iron during mechanical activation and sintering in air. Magnetic properties of samples sintered at 1200 o C are superior to those sintered at 1100 o C, which can be attributed to higher Ba 2 Fe 22.46 O 38 Ti 1.54 phase content. The position of the Curie temperature in 350-420 o C temperature region is consistent with 0.8:1 ratio of Ti to Ba. Maximum magnetization was observed for samples activated for 120 min. Dielectric properties of samples sintered at 1200 o C showed a dependence on frequency, with a significant drop in relative permittivity with an increase in

Effects of mechanical activation on the formation and sintering kinetics of barium strontium titanate ceramics

“…A general trend of the increase in the values of activation energy at higher values of relative density suggests that there is an increase in the length of diffusion paths as the samples become more compact and particle size increases during sintering, leading to a higher barrier for further mass transport. Prolonged mechanical activation results in higher relative densities observed both at the beginning and the end of the sintering process, indicating a more compact final product, which is typically associated with improved functional properties [48,49]. Morphology of different BST samples with different composition, mechanically activated and sintered, is presented in Figs 8-10.…”