Microscopic study of grain-boundary region in polycrystalline ferrites

Abstract

The nature of grain boundary of manganese zinc ferrites is critical for magnetic properties. Many studies on grain-boundary structure and chemistry have been done, and those experimental results do not seem to fully describe the magnetic properties. In this study, close analysis of the grain-boundary region using high-resolution electron microscopy has made it clear that each grain consists of many small regions of 5–10 nm in size. The crystallographic orientation of each region is slightly different from each other in the order of 0.1–0.4°. And some defects are observed in lower permeability ferrites. Auger microprobe analyses clarify the segregation of Ca and Si and increase of Fe/O ratio at the grain boundary. The structural features will be discussed in relation to segregation and change of composition at the grain boundary.