Magnetic Characteristics and Microstructure of Some Ferrite Antenna and Inductor Cores Doped with Co, Ca, and Si
This work gives accounts of an attempt to produce two types of commercial ferrite material whose magnetic characteristics were to be studied in relation to some additives and the microstructure. Two compositions, MgZn- and NiZn-based ferrites, were prepared by the oxide method and characterised m...
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| Format: | Thesis |
| Language: | English English |
| Published: |
1996
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/8604/1/FSAS_1996_2_A.pdf |
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| Summary: | This work gives accounts of an attempt to produce two types of commercial
ferrite material whose magnetic characteristics were to be studied in relation to some
additives and the microstructure. Two compositions, MgZn- and NiZn-based ferrites,
were prepared by the oxide method and characterised mainly in terms of magnetic
properties and microstructure. The former composition was to be used as the material
for antenna bars and the latter for high-frequency inductors. The antenna material was
shaped into bars and toroids while the inductor material into rectangular plates and
toroids. The properties of the two compositions were investigated as functions of the
amount of additives (CaD and Si02 and CoO). The influence of sintering temperature and forming pressure on magnetic and mechanical properties and average grain size
was also studied. The experimental investigation consists of three parts.
Firstly, various compositions of MgZn-based territes were prepared and the
properties upgraded by suitable additions of CaO and SiOl. The inexpensive raw
material powder MgO was used to substitute NiO in a composition of commercial
NiZn-based ferrite commonly used for antenna bars. A MgZn-territe composition with
properties matching the commercial material's properties was successfully obtained.
Secondly, the effect of directly-added CoO to MgZn- and NiZn-based ferrites
was studied. The addition of CoO for these two original compositions decreased the
initial permeability and minimised the variation of initial permeability with
temperature. However. the frequency range and the Curie temperature increased with
the increase of CoO content. The variations of the properties as a function of the
amount of CoO were discussed in tenns of the contribution of C0²⁻ ions to
magnetocrystalline anisotropy.
Thirdly, intentional changes of microstructure for both original compositions
were made by varying the forming pressure and sintering temperature. No significant
changes on magnetic and mechanical properties and microstructure were found with
the increase of forming pressure. However, the average grain size increased with the sintering temperature, thus, influencing the magnetic and mechanical properties of the
samples. The initial penneability increased linearly with grain size. |
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