TWI573772B - Mn-zn ferrite powder - Google Patents

Description

Mn-Zn ferrite powder

The present invention relates to a manganese-zinc ferrite magnetic powder, and more particularly to a manganese-zinc ferrite magnetic powder which can be used in an amplifying circuit to produce a high squareness ratio magnetic core.

Mn-Zn ferrite cores have the advantages of high resistivity, initial permeability, saturation flux density, Curie temperature and low iron loss, so they are widely used in switching power transformers, using the characteristics of their saturated inductors, feedback To control the power transformer. Generally, in the magnetic properties, a high squareness ratio (Squareness ratio) represents a square ratio of magnetic hysteresis curve (Br/Bs, Br: residual magnetic induction, Bs: saturation magnetic induction), and a low coercive force (Hc) can be utilized. Saturation can be achieved to control the stability of the initial voltage of the power transformer. Among them, Bs high will be higher than the signal to noise ratio. In addition, the magnetic permeability (μi) is high to reduce the core volume, and the core magnetic loss is low to avoid heat and waste energy.

U.S. Patent No. 2,715,109 discloses the use of 5 to 60 mol% of manganese oxide (MnO), 8 to 50 mol% of magnesium oxide (MgO), and 25 to 50 mol% of ferric oxide (Fe ₂ O ₃ ). and 0.5 ~ 7mol% of other metal oxides such as calcium oxide (CaO), cadmium oxide (CdO), yttria (Y ₂ O ₃₎ and other magnetic formulated. As shown in the first and second embodiments, although the rectangular ratio of the obtained magnetic core is 90 to 95%, the magnetic permeability is low, only 40 to 45, and the Hc is about 0.65 to 1.5, and the Bs is about 1780. 2000 Gauss, did not mention the related improvement method of magnetic loss.

In addition, a magnetic core made of 40 to 53 mol% of ferric oxide, 1 to 30 mol% of copper oxide (CuO), and 20 to 60 mol% of manganese oxide is also disclosed in the U.S. Patent No. 2,818,387. Although the ratio is 71~90%, but Bs is only 700~1905 Gauss, there is no mention of the magnetic loss and magnetic permeability improvement method.

Therefore, it is necessary to provide a manganese-zinc ferrite magnetic powder, which can produce a magnetic core having a high squareness ratio, excellent magnetic characteristics, and low magnetic loss to solve the problems of the conventional technology.

The main object of the present invention is to provide a manganese-zinc ferrite magnetic powder, adjusting the ratio of ferric oxide, manganese oxide and zinc oxide, and adding a small amount of auxiliary components, and the magnetic core prepared by the manganese-zinc ferrite powder after sintering has The high squareness ratio and excellent magnetic properties make it possible to achieve low magnetic loss, high magnetic permeability and low coercive force in a wide temperature range of 25 to 100 ° C, which is particularly advantageous for use in a switching power transformer.

To achieve the above object, an embodiment of the present invention provides a manganese zinc ferromagnetic powder comprising: a main component comprising 48.9 to 50 mol% of ferric oxide (Fe ₂ O _{3 )} in mole percent 47.5 to 51.5 mol% of manganese oxide (MnO); and 0 to 2.70 mol% of zinc oxide (ZnO), and the sum of the ferric oxide, the manganese oxide and the molar percentage of the zinc oxide is 100 mol% And a component comprising, in an amount of 100 parts by weight based on the total weight of the main component, 0.02 to 0.04 parts by weight of bismuth trioxide (Bi ₂ O ₃ ); and 0.05 to 0.08 parts by weight of three Molybdenum oxide (MoO ₃ ).

In an embodiment of the invention, the molar ratio of the ferric oxide and the manganese oxide is ferric oxide: manganese oxide = 1:0.95 to 1.05.

In an embodiment of the invention, the manganese zinc ferrite powder has a particle diameter of 1.1 to 1.2 micrometers (μm).

The above and other objects, features, and advantages of the present invention will become more apparent from In addition, the singular forms "a," "," For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof; "%" as referred to in the present specification means "percent by weight (wt%)" unless otherwise specified; For example, 10%~11% of A) include upper and lower limits (ie 10% ≦A≦11%) unless otherwise specified; if the value range does not define a lower limit (such as B below 0.2%, or 0.2) B) below B) means that the lower limit may be 0 (ie 0% ≦ B ≦ 0.2%); the proportional relationship of the "weight percentage" of each component may also be replaced by the proportional relationship of "parts by weight". The above terms are used to illustrate and understand the present invention and are not intended to limit the invention.

An embodiment of the present invention provides a manganese zinc ferromagnetic powder comprising a main component and a subcomponent. The main component comprises 48.9 to 50 mol% of ferric oxide (Fe ₂ O ₃ ), 47.5 to 51.5 mol% of manganese oxide (MnO), and 0 to 2.7 mol% of zinc oxide (ZnO) in terms of a percentage of moles, and The sum of the ferric oxide, the manganese oxide and the molar percentage of the zinc oxide is 100 mol%. Preferably, the molar ratio of the ferric oxide and the manganese oxide is ferric oxide: manganese oxide = 1:0.95 to 1.05. Further, the total weight of the main component is 100 parts by weight, and the subcomponent contains 0.02 to 0.04 parts by weight of bismuth trioxide (Bi ₂ O ₃ ) and 0.05 to 0.08 parts by weight of the third component. Molybdenum oxide (MoO ₃ ). For example, if the MnZn ferromagnetic powder comprises a main component having a total weight of 100 g; the MnZn ferromagnetic powder further comprises a subcomponent having 0.02 to 0.04 g of bismuth trioxide (Bi ₂ O ₃ ) and 0.05 Up to 0.08 grams of molybdenum trioxide (MoO ₃ ).

Further, the particle size of the MnZn ferromagnetic powder is preferably from 1.1 to 1.2 μm. The magnetic core made of the Mn-Zn ferromagnetic powder has excellent magnetic properties, and the Br/Bs of the hysteresis curve is measured at a squareness ratio of 25 ° C at an operating temperature range of 25 to 100 ° C. : Residual magnetic induction, Bs: saturation magnetic induction) calculated from a rectangular ratio greater than 89%, a magnetic permeability (μi) greater than 250, a coercive force (Hc) less than 0.65 Å, and a saturation magnetic induction (Bs) greater than 4100 Gauss. According to an embodiment of the invention, the manganese-zinc ferrite core obtained by the manganese-zinc ferrite magnetic powder has a magnetic loss per unit volume of PL _{25 kHz-0.2 T-100 ° C of} less than 330 kW/m 3 _{at 100 ° C.} Preferably, the Mn-Zn ferrite core of less than 300 kilowatts per unit volume of the magnetic loss of 120 ℃ PL _{25KHz-0.2T-120 ℃} / m ^. Therefore, the manganese zinc ferrite powder of the present invention is advantageously used in a magnetic amplification circuit.

In order to verify the magnetic properties of the MnZn ferromagnetic powder of the present invention, please refer to the actual manufacturing process described below. However, the manufacturing method is merely an example, and is not intended to limit the processes, steps, and product components thereof.

Preparation of manganese-zinc ferrite magnetic powder and magnetic core: mixing the main components of ferric oxide, manganese oxide and zinc oxide into a furnace, simmering at 900 ° C for 60 minutes, cooling to room temperature 25 ° C, and then The subcomponents are mixed with the main component after the above calcination. The proportions of the main components and subcomponents are shown in Table 1 below.

Next, wet milling was carried out to obtain a manganese-zinc ferrite powder having a particle diameter of about 1.1 to 1.2 μm, and a binder of 1 wt% of polyvinyl alcohol (PVA) was added to the above mixture, followed by manual sieving. Then, granulation is carried out to form granules, and the granulated powder has a particle diameter of 80 to 240 μm. The granulated particles are then molded into a green body of a desired shape by a mold, for example, an embryo having an outer diameter × an inner diameter × a thickness = 8 × 4 × 5 mm (mm), and the green embryos are subjected to the following procedures (a) to (e). After sintering sequentially, a manganese-zinc ferrite core having a high squareness ratio of more than 89% can be obtained, and its grain size is about 15 μm.

(a) heating at a heating rate of 100 ° C / hour for about 6 hours up to 600 ° C; (b) heating at a heating rate of 200 ° C / hour for about 1.5 hours up to 900 ° C; (c) heating at 250 ° C / hour Rate, heating for about 1.68~1.8 hours until 1320~1350 °C, then holding for 2.5 hours; (d) cooling at about 200 °C / hour, about 1.1~1.25 hours until 1100 °C; and (e) at 240 °C / The cooling rate of the hour was cooled from 1100 ° C for about 4.8 hours to normal temperature.

The oxygen content in the above process is reduced to less than 2% above 600 °C, and the temperature rising section 600 ° C (ie (b) ~ (c)) begins to reduce the oxygen content of air 21% to less than 2% oxygen content, and then maintain 2% oxygen content until the end of the cooling section.

Measurement of magnetic properties: The obtained magnetic core measures the hysteresis curve at 25 ° C and 100 ° C to obtain a squareness ratio thereof. Other magnetic properties such as: permeability μi can be measured at 100KHz using the magnetic permeability measuring device Agilent-4284A (LCR meter); magnetic loss per unit volume PL at 100 ° C and 120 ° C is measured by Iwatsu-8232; coercive force Hc The saturation magnetic induction intensity Bs and the residual magnetic induction intensity Br are measured by a YEW-3257 BH tracer tester under direct current. The detailed data of each group of manganese-zinc ferrite powders are shown in Table 2 below.

As can be seen from Tables 1 and 2, the magnetic powder of Comparative Example 1 contained less than 48.9 mol% of ferric oxide, and its Bs was lower than 4100 and 3500 Gauss at 25 ° C and 100 ° C, respectively, so that the signal-to-noise ratio was not sufficiently high. In Comparative Example 2, the zinc oxide contained in the magnetic powder is higher than 2.7 mol%, and the addition of molybdenum trioxide exceeds 800 ppm, and the squareness ratio is less than 89% and 65% at 25 ° C and 100 ° C, respectively, and the signal-to-noise ratio is not high enough. And the purpose of rapid feedback stability control cannot be achieved. Similarly, Comparative Example 3 contained less than 47.5 mol% of manganese oxide, and its squareness ratio was less than 89% and 65% at 25 ° C and 100 ° C, respectively, which made the signal-to-noise ratio insufficient and could not achieve rapid feedback and stable control.

The manganese-zinc ferrite magnetic powder according to the embodiments 1 to 4 of the present invention can form a manganese-zinc ferrite core having excellent magnetic properties, and the squareness ratio is greater than 89% and permeability at an operating temperature range of 25 to 100 °C. (μi) is greater than 250, coercive force (Hc) is less than 0.65 Å (Oe), and saturation magnetic induction (Bs) is greater than 4100 Gauss (G). In addition, the manganese-zinc ferrite powders of Examples 1 to 4 can achieve a magnetic loss rate per unit volume of 100 ° C PL _{25 KHz-0.2 T-100 ° C} less than 330 kW / m ^ 3 , and a magnetic loss per unit volume at 120 ° C PL _{25KHz-0.2T-120 °C is} less than 300 kW / m ^ 3, reducing magnetic loss can effectively avoid heat and waste energy.

The present invention has been disclosed in its preferred embodiments, and is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application.

Claims (3)

A manganese-zinc ferrite magnetic powder comprising: a main component comprising 48.9 to 50 mol% of ferric oxide; 47.5 to 51.5 mol% of manganese oxide; and 0 to 2.70 mol% of zinc oxide, and The ferric oxide, the sum of the manganese oxide and the molar percentage of the zinc oxide is 100 mol%; and a subcomponent having a relative weight of 100 parts by weight based on the total weight of the main component: 0.02 to 0.04 Parts by weight of antimony trioxide; and 0.05 to 0.08 parts by weight of molybdenum trioxide. The manganese-zinc ferrite magnetic powder according to claim 1, wherein the molar ratio of the ferric oxide and the manganese oxide is ferric oxide: manganese oxide = 1:0.95 to 1.05. The manganese-zinc ferrite magnetic powder according to claim 1, wherein the manganese-zinc ferrite powder has a particle diameter of 1.1 to 1.2 μm.