Role of \Bi2{\O}3 Additives on the Microstructure Development and Magnetic Properties of NiCuZn-Tb Ferrites.

The role of \Bi2{\O}3 addition on the structural and magnetic properties of NiCuZn-Tb ferrites with composition \Ni0.5{\Cu}0.25{\Zn}0.25{\Tb}0.1{\Fe}1.9{\O}4+{\xBi}2{\O}3 has been investigated, where values of x (in wt %) are 0, 1, 2 and 3. Samples were prepared by the sol-gel auto combustion synthesis. The crystallographic, structural and magnetic properties of the samples were investigated by X-ray diffraction (XRD), scanning electron micrography, vibrating sample magnetometer and permeability measurements. Cubic spinel structure was observed from the XRD pattern for all the samples, implying that the \Bi2{\O}3 additives did not form a visible second phase in \leq 2 wt% of \Bi2{\O}3. Microstructural studies showed that \Bi2{\O}3 forms a liquid-like phase and promotes the grain growth. The average grain size increased for \leq 2 and then decreased for > 2 wt% of \Bi2{\O}3 content. The maximal grain size appears with 2 wt% \Bi2{\O}3. These characteristics evidently affect the magnetic properties, such as saturation magnetization (Ms) and permeability of the NiCuZn-Tb ferrites. \Bi2{\O}3 increase the Ms, bulk density (dB) and permeability effectively, while excessive \Bi2{\O}3 concentration results in the abnormal grain growth and decrease of Ms and dB. [ABSTRACT FROM PUBLISHER]