| Ways to advance coercivity | | | | Al and Cr will replace Fe ion of crystal, coercivity is |
| Magnetic experts said that the difference of plumbum | | | | advanced, but Br will lower a little. |
| shape of magnet and spinel shape of magnet are | | | | In A formula, if second additive becomes to: 0.6% |
| “R block” where is unavailable for | | | | CaCO3, 0.8% SrSO4, 1.0% Cr2O3, 0.4% Al2O3, the |
| less-symmetrical hexahedron 2b crystal to spinel | | | | magnetic parameter becomes to: 397mT Br, |
| ferrite. Fe3+ has such a great interplay of anion around | | | | HCB?276kA/m, HCJ?288kA/m, (BH)max:29kJ/m3; |
| triangle particle fields that yields a anisotropic higher | | | | adding SrSO4 can increase the activity of magnetic |
| than cubic crystal. That is to say, Fe3+ supply a higher | | | | material and advance the value of Br and HC. |
| anisotropic in the 2b. Besides 2b, 12k and Fe3+ on | | | | In A Formula, if the second additive changes to: 0.6% |
| other positions make a good contribution to anisotropic. | | | | CaCO3, 0.8% SrSO4, 1.0% Cr2O3, 0.4% Al2O3, the |
| To advance the coercivity by mechanism, we have | | | | magnetic performance parameter will change to: |
| gained a certain progress. Magnetic remanence value | | | | Br?390mT, HCJ?310kA/m. |
| Br has been very near to the theoretic value in | | | | B. if adding some SrCO3 in the second additive, it will |
| industry production, while the value of coercivity are still | | | | help to generate M phase and complete growth of |
| 1/3 less than the theoretic value-616ka/m(Sr ferrite) at | | | | broken crystal particle, If SiO2 is added into the second |
| least. | | | | additive, it will assemble on the ferrite crystal particles |
| Following are common ways to advance coercivity in | | | | to strengthen the surface resistance and prevent the |
| industrial manufacturing process | | | | crystal from growing. When the adding rate exceeds |
| 1. make the size of particle distributed on average at | | | | 0.2%, the force of coervicity will increase. Surely, it is |
| state of single domain, the particle size of single | | | | also favorable to advance coervicity by lowing the |
| domain for permanent magnetic ferrite are around 0.9u | | | | temperature of sintering or shortening the |
| normally. Under the condition of single domain, the | | | | attemperation time on the artwork. The way to make |
| magnet vector is enabled to rotate and Hcj is higher. In | | | | high performance permanent ferrite |
| facts, the single domain and multi domain are | | | | Just as mentioned in many files, the efficiency of |
| co-existence under mass production. The core of | | | | molding will be low and make it more complicated |
| anti-magnetization is still coming up and the magnet | | | | through milling the particle of permanent magnetic |
| vector is also rotated. Analyzer is important for | | | | ferrite. It will decrease Br to improve coercivity through |
| researching the manufacture machinery and the | | | | add oxid such as Al or Cr. If want to get coercivity up |
| particle of single domain. Now people are using | | | | to 320kA/m(over 4000Oe), meanwhile to keep the |
| average particle size analyzer step by step to test | | | | value of Br below 400MT or less, it can be hit through |
| particle size distribution, balling mill and grinder are used | | | | ion replacement which is certificated feasible in results |
| for making particle of single domain. Avoid using the | | | | of research and practice by many experts. The |
| vibrating mill as possible can prevent forming sheet | | | | property of mass production is as follow: |
| shape particle. | | | | 1. Br:426mT, HCB:297.3kA/m, HCJ:371.7kA/m, |
| 2. it is an important method to advance coercivity by | | | | (BH)max:34.3kJ/m3 |
| adjusting the formula and manufacture technology. | | | | 2. Br:4260Gs, HCB:3735Oe, HCJ:4670Oe, |
| The formula value “n” has some effects on | | | | (BH)max:4.31MGOe |
| coercivity. When n6, change the formula additive and | | | | It is feasible to choose oxide of rare earth La and |
| manufacturing technology, the coercivity can reach | | | | oxide of Co to replace hexangular crystal Sr ion and |
| 400ka/m or above, and Br will also reach above | | | | Fe ion of permanent magnetic ferrite, whose ionic |
| 400mt. Under special condition, when rate of mol | | | | radius is nearly the same. If keeping the number of ion |
| comes to 8 for Fe2O3 and SrCO3, which can lead | | | | the same in the replacing process, and balancing the |
| both Br and Hcj to theoretic value. | | | | compensate charge, it can advance the coervicity and |
| Herein comes a discussion on the change of coercivity | | | | Br greatly. By proving of testing, its property is best |
| value under n=6.1 when altering the additive: | | | | when the adding weight rate is within 0.5—5%, |
| A. n=6.1, both first additive and second additive are: | | | | TDK have released FB9 series, some labs of our |
| 0.4% CaCO3 and 0.4% kaolin | | | | country have also produced the same grade of |
| Magnetic parameters: Br:390mT, HCB:180kA/m, | | | | permanent magnetic ferrite with FB9, which is near the |
| HCJ:190ka/m, (BH)max:27.5kJ/m3 | | | | theoretic value of permanent magnetic ferrite. |
| In A formula, when adding 0.7% Cr2O3 and 0.6% | | | | Innovation for old products should include heighten |
| Al2O3 the second time, the magnetic performance | | | | produce efficiency, lowing cost and creating new |
| becomes to: Br?380Mt, HCB?250ka/m, HCJ?270ka/m, | | | | technical artwork besides improving parameters. |