How many basic classifications are there for ferrite core materials?

Ferrite is a permanent magnet material made of iron oxide and alkaline earth metal oxides (such as SrO or BaO), also known as hard ferrite. They are made by ceramic processes (including pre-firing, crushing, grinding, pressing, sintering and grinding) and have a wide hysteresis loop, high coercivity and high remanence, capable of maintaining constant magnetism once magnetized. The crystal structure and chemical composition of ferrite are one of its basic characteristics.

In the ferrite crystal structure, oxygen ions are the densest, and they form a tightly packed three-dimensional structure. Iron and transition metal ions are inserted between these oxygen ions to form the crystal structure. Iron ions can be in two oxidation states, +2 and +3, while transition metal ions can be elements such as iron, zinc, nickel, and manganese.

The crystal structure of ferrite is highly symmetrical and usually appears as cubic, tetragonal and hexagonal systems. In these different crystal systems, the lattice constant, cell volume and cell symmetry of ferrite crystals are also different. The location and number of transition metal ions in the crystal structure of ferrite also affect its physical and chemical properties. In addition, the relative ratio between iron oxide and transition metal oxide also has an effect on the properties of ferrite.

Depending on the process, ferrite permanent magnets can be divided into two types: sintered ferrite and bonded ferrite. Sintered ferrite can be divided into dry pressing and wet pressing, bonded ferrite can be divided into extrusion molding, injection molding and rolling molding. There are two families of ferrite permanent magnets: isotropic and anisotropic. According to different forming processes, anisotropic ferrites can be divided into dry pressing and wet pressing. According to the classification of main components, ferrite permanent magnets are mainly divided into barium ferrite and strontium ferrite. Barium ferrite is the most widely used permanent magnet material on the market.

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