Abstract
Low temperature sintering of microwave magnetic materials, Bi-incorporated CVG materials, (Bi0.75Ca1.2Y1.05)(V0.6Fe4.4)O12, was investigated. Sintering behavior and magnetic properties of Bi-CVG materials prepared using nano-sized powders were compared with those of the materials prepared from micron-sized powders and these of microwave sintered samples were also compared. The activation energy for densification (Ed), which was derived from temperature and time dependence of materials’ density, is markedly reduced by using nano-sized powders as starting materials, viz. (Ed)nano=7.04 kJ/mole and (Ed)□=39.5 kJ/mole for nano-powder and micron-powder derived samples, respectively. The activation energy for densification is even more pronouncedly lowered by using microwave sintering process that is, (Ed)ms=4.59 kJ/mole. However, the activation energy for grain growth is not pronouncedly different for the two categories of materials ((Eg)nano=40.4 kJ/mole and (Eg)□=73.5 kJ/mole). The saturate magnetization (Br) of the Bi-CVG materials is the same, as long as the samples possess the same high density, whereas, the coercive field (Hc) of the materials is larger for fine grain samples and vice versa. The low frequency magnetic properties of the Bi-CVG materials are microstructural dependent, while the microwave magnetic properties of the materials are not. Whether the materials were prepared from nano-sized or micron-sized materials and sintered by conventional or microwave sintering process is not a predominating factor.