Effects of the addition of SiO
2-CaO and the partial pressure of oxygen in the sintering process on the grain growth and magnetic properties of Mn-Zn ferrite were studied to obtain a fine grain structure as well as superior magnetic properties. The results obtained are summarized as follows.
(1) With the addition of SiO
2-CaO up to 0.05 mass%, the density of Mn-Zn ferrite decreased, beyond which it increased inversely up to 0.2 mass% of SiO
2-CaO.
(2) After a significant increase with the addition of 0.02 mass% of SiO
2-CaO, the electrical resistivity showed a rapid decrease at 0.05 mass% addition and then an increase up to the addition of 0.20 mass% of SiO
2-CaO.
(3) Fine grains were observed in the specimen without the addition of SiO
2-CaO. In the specimen with the addition of SiO
2-CaO, its grains became coarsened with the addition up to 0.05 mass%, while they
showed a tendency to become finer with the addition of more than 0.05 mass%.
(4) The Q values at the frequencies from 0.1 to 5.0 MHz varied in a similar way to the resistivity when the addition of SiO
2-CaO increased. However, the μ values varied in a different way from the resistivity, and μ with the addition of 0.05 mass%SiO
2-CaO showed a maximum at 0.1 MHz, and this maximum decreased and changed to a minimum when the frequency increased up to 5.0 MHz.
(5) Grains of the specimen with the addition of 0.05 mass%SiO
2-CaO became coarsened with increasing O
2 partial pressure up to 1.0%, while they became finer with the values more than 1.0%. Corresponding to this tendency of grain size, the density decreased with the increase of O
2 partial pressure up to 100%. On the other hand, the resistivity was very low at 0.01% of O
2 partial pressure and showed a remarkable increase at 0.05%. Beyond this point, the resistivity decreased with the increase of O
2 partial pressure up to 1.0%, and then it increased up to 100%.
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