Tailoring the temperature characteristics of the magnetic permeability of NiZn ferrites

Tsakaloudi, V.; Zaspalis, V.T.

doi:10.1016/j.jmmm.2009.10.007

Cited by 7 publications

(1 citation statement)

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“…Finally, it is worthwhile to mention that, as indicated in Figure 4c, sintering in Nitrogen atmospheres leads to faster densification. Although this process is not compatible with modern industrial NiCuZn-ferrite production where sintering takes place in the air, as found earlier [27], it leads to lower permeabilities and losses higher by a factor of almost 2 when compared to those achieved when sintering takes place in the air.…”

Section: Resultsmentioning

confidence: 80%

The Effect of Sintering Temperature on the Densification and Magnetic Performance of NiCuZn-Ferrites (CuO: 0–6 wt.%)

Zaspalis,

Kogias,

Zaspalis

2024

Materials

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This article reported on the effect of Cu-content and sintering temperature on the magnetic permeability and power losses of monolithic iron-deficient NiCuZn-ferrite components with low Cu-contents aimed to be used for power applications at frequencies up to 1 MHz. In particular NiαZnb1−xCuxFe1.9O4 ferrite compositions are investigated with a constant Ni/Zn atomic ratio a/b = 0.9 and 0 < x < 0.017. As found, the addition of Cu enables the achievement of good magnetic performance at lower sintering temperatures and, therefore, lower production cost. At all Cu-contents, the initial permeability as a function of the sintering temperature passes through a maximum above which structural deterioration due to asymmetric grain growth occurs. The temperature at which this maximum permeability occurs depends on the Cu content and coincides with the achievement of the maximum density of 5.1–5.2 g cm−3 (relative density ~97%). At Cu-contents x = 0.006–0.012 and sintering temperatures 1200–1100 °C power losses (tan(δ)/μ at 1 MHz, 25 °C) οf 50 × 10−6 could be achieved and initial permeabilities (10 kHz, 0.1 mT, 25 °C) of around 400 with very good frequency and temperature stability. At CuO content higher than 4 wt.% (i.e., x > 0.012) and sintering temperatures higher than 1150 °C, pronounced microstructural disturbances due to asymmetric grain growth result in low permeabilities and high losses. It is suggested that at low CuO contents and low sintering temperatures, the densification enhancement may not proceed through Cu-rich phase segregation but through the creation of oxygen vacancies.

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Section: Resultsmentioning

confidence: 80%