Specialty materials processing techniques for enhanced resonant frequency hexaferrite materials for antenna applications and other electronic devices
View Patent ↗Processing techniques for forming a textured hexagonal ferrite materials such as Z-phase barium cobalt ferrite Ba 3 Co 2 Fe 24 O 41 (Co 2 Z) to enhance the resonant frequency and other magnetic properties of the material for high frequency applications are provided. The processing techniques include magnetic texturing by using fine grain particles and sintering the material at a lower temperature than conventional firing temperatures to inhibit reduction of iron. The processing techniques also may include aligning M-phase (BaFe 12 O 19 uniaxial magnetization) with non-magnetic additives in a static magnetic field and reacting with BaO source and CoO to form Z-phase (Ba 3 Me 2 Fe 24 O 42 ). In some implementations, processing techniques includes aligning Co 2 Z phase (planar magnetization) with magnetic texturing occurring in a rotating magnetic field.
1. A method of increasing the resonant frequency of a hexagonal ferrite material, comprising:
forming a fine grain hexagonal ferrite powder comprising Z-phase barium cobalt ferrite having the formula Ba 3 Co 2 Fe 24 O 41 and having an average particle size of between 300-600 nm; and
firing the hexagonal ferrite powder at a sintering temperature selected to form a hexagonal ferrite material having reduced magnetorestriction.
2. The method of claim 1 further comprising compacting the hexagonal ferrite powder prior to firing.
3. The method of claim 1 wherein the fine grain hexagonal ferrite powder has an average surface area of greater than 6 m 2 /g.
4. The method of claim 1 wherein the sintering temperature is between 1100 and 1250° C.
5. The method of claim 3 wherein the fine grain hexagonal ferrite powder has an average surface area of greater than 15 m 2 /g.
6. The method of claim 1 wherein the fine grain hexagonal ferrite powder is formed by a process selected from the group consisting of co-precipitation, sol-gel, and mechanical milling.