DE1671033B1 - USE OF STRONTIUM FERRITE AS A PERMANENT MAGNETIC MATERIAL - Google Patents

Description

The invention relates to the use of sulfate and silicon-containing strontium ferrite of the basic composition of SrO · χ Fe ₂ O ₃ as a permanently magnetic material.

It is already known that, of the so-called magnetoplumbite ferrites, the strontium ferrite is distinguished by the best permanent magnetic properties under certain conditions. It is known that strontium ferrite with a strontium sulfate content of 0.1 to 2 percent by weight has a high magnetic energy product. The optimum value of the magnetic energy coefficient has so far been found in substoichiometric ferrites of this type, ie that χ, that is the molar ratio between Fe ₃ O ^ and SrO, has values between 5 and 6. When using strontium carbonate as one of the ferrite-forming starting substances, a range between 10 and 25 percent by weight has been specified with an optimum of 15.2 percent by weight. This corresponds to a molar ratio χ = 5.6. It is also known that the properties of such ferrites can be improved by adding silicon dioxide up to 2 percent by weight.

By "Journal of Applied Physics", 27, pp. 1052 and 1053 (1956), "Advanced Physics", 8, p. 152 (1959), and “Compt. rde. ”, 242, from June 1956, pp. 2817/2820, ferrites with a coercive force of up to 10,000 Oe are already known. The remanence induction in these ferrites is, however, at an undesirably low level Decreased value.

The invention is based on the object, the magnetic Ettergiepfödukt and in particular the To increase the coercive field strength of such sulfate- and silicon-containing Strontiuiriterrite. A big Coercive force is especially essential when the material is highly demagnetizing Fields is exposed because the permanent magnetic strontium ferrite is at high coercive force behaves practically insensitive to demagnetizing fields. The magnetic energy product is a quality factor for permanent magnetic bodies.

On the basis of extensive investigations

confirms that in the range between χ = 5 and 6 optimal magnetic properties can be achieved with strontium ferrite. However, it was surprisingly found that, depending on the molar ratio between Fe ₂ O ₃ and SrO, very different proportions of strontium sulfate and silicon dioxide are required in order to achieve really optimal properties.

ao ten, in particular to arrive at optimally high coercive field strengths. The general statement, e.g. B. to use up to 2 percent by weight of SrSO ₄ is not yet able to convey a directly practicable teaching to your skilled person for achieving the best possible magnetic values.

The invention consists in specifying precisely defined optimal proportions of strontium sulfate and silicon dioxide as a teaching for technical action for special molar ratios between χ = 4.4 and χ = 6.5. This is specified in more detail in the following table.

Fe ₂ O ₃ : SrO
Mole SrSO ₄
Weight percent SiO ₂
Weight percent kOe Sr
kG (ßH) _max
MGOe 4.1 0.85 to 1.45 1.85 to 2.15 4.0
2.0 3.3
3.8 2.5
3.1 4.4 0.8 to 1.4 1.4 to 1.8 4.1
2.8 3.3
3.8 2.6
3.3 4.7 0.8 to 1.4 1.0 to 1.4 4.2
3.0 3.3
3.8 2.7
3.4 5.1 0.7 to 1.3 0.6 to 1.0 4.25
3.4 3.3
3.8 2.7
3.5 5.5 0.4 to 1.4 0.2 to 0.6 4.3
3.7 3.3
3.8 2.7
3.45 6.0 0.3 to 1.0 0.3 to 0.7 4.15
2.8 3.3
3.8 2.6
3.3 6.5 0.2 to 0.8 0.35 to 0.75 4.1
2.1 3.3
3.8 2.5
3.2

With reference to FIGS. 1 and 2, the invention is nodh explained in more detail.

In FIG. 1 shows the coercive field strength with constant remanence induction of B _r = 3.8 kG as a function of the molar ratio χ for various strontium ferrites. Curve A applies to strontium ferrite free of strontium sulfate and silicon dioxide. The coercive field strength is increased considerably by adding strontium sulfate. About the same increase can be achieved by adding silicon dioxide instead of strontium sulfate. With the addition of both components, namely strontium sulfate and silicon oxide, an extraordinarily large coercive field strength is achieved, which goes far beyond the pure liquid effect of the two individual compositions. The "proportions of the additives are chosen in such a way that * maximum iH _c values are achieved with the same remanence induction.

In FIG. 2, the optimal ranges of the strontium sulfate content and the silicon dioxide content that apply to various molar ratios X are shown. For a molar ratio χ = 4.1, the optimum range is between approximately 0.85 and 1.45 percent by weight SrSO ₄ and between 1.85 and 2.15 percent by weight SiO ₂ . The optimal range with regard to the coercive field strength of this strontium ferrite is therefore partly outside of the previously known circumscribed _{by the lines I 3 2 and 3}

th share range. With an increasing molar ratio between the iron oxide and the strontium oxide up to about χ = 5.5, the optimal ranges are surprisingly found with lower silicon oxide contents. The proportion of strontium sulfate for the optimum ranges also decreases, albeit to a much lesser extent. For a molar ratio χ = 6.0 or more, the silicon oxide proportion increases again for the optimum range, while the strontium sulfate proportion decreases more sharply. The enveloping curve U indicates the total range of optimally achievable values for the molar ratios between χ = 4.1 and χ = 6.5.

The magnetic values given in the table relate to those which can be used according to the invention Strontium ferrite with a magnetic anisotropy, the magnetic values in the magnetic Preferred direction are measured.

Claims (7)

Claims: 20 1. Use of strontium ferrite with a basic composition of SrO.4.1 Fe ₂ O ₃ , an SrSO ₄ content of 0.85 to 1.45 percent by weight and an SiO ₂ content of 1.85 to 2.15 percent by weight as a permanent magnet Material. 2. Use of strontium ferrite with a basic composition of SrO.4.4 Fe ₂ O ₃ , an SrSO ₄ proportion of 0.8 to 1.4 percent by weight and an SiO ₂ proportion of 1.4 to 1.8 percent by weight as a permanent magnet Material. 3. Use of strontium ferrite with a basic composition of SrO.4.7 Fe ₂ O ₃ , an SrSO ₄ proportion of 0.8 to 1.4 percent by weight and an SiO ₂ proportion of 1.0 to 1.4 percent by weight as a permanent magnet Material. 4. Use of strontium ferrite with a basic composition of SrO.5.1 Fe ₂ O ₃ , an SrSO ₄ content of 0.7 to 1.3 percent by weight and an SiO ₂ content of 0.6 to 1.0 percent by weight as a permanent magnet Material. 5. Use of strontium ferrite with a basic composition of SrO.5.5 Fe ₂ O ₃ , an SrSO ₄ proportion of 0.4 to 1.4 percent by weight and an SiO ₂ proportion of 0.2 to 0.6 percent by weight as a permanent magnet Material. 6. Use of strontium ferrite with a basic composition of SrO · 6.0 Fe ₂ O ₃ , an SrSO ₄ proportion of 0.3 to 1.0 percent by weight and an SiO ₂ proportion of 0.3 to 0.7 percent by weight as a permanent magnet Material. 7. Use of strontium ferrite with a basic composition of SrO · 6.5 Fe ₂ O ₃ , an SrSO ₄ proportion of 0.2 to 0.8 percent by weight and an SiO ₂ proportion of 0.35 to 0.75 percent by weight as permanent magnetic material. 1 sheet of COPY drawings