KR20200069908A - A ferri-magnetic material and method of preparaing the magnetic material - Google Patents

Abstract

According to one aspect, an object of the present invention is to provide a magnetic material having a high coercive force including an ε-Fe_2O_3 phase without a medium, and a manufacturing method thereof. The present invention relates to the magnetic material containing the ε-Fe_2O_3 phase, not including a Y_3Fe_5O_12 phase prepared by heat-treating mixed powder of a yttrium precursor and an iron precursor.

Description

A ferri-magnetic material and method of preparaing the magnetic material

It relates to a magnetic material and a method for manufacturing the same.

In the magnetic field such as magnetic printing and wireless communication, a magnetic material is used as a medium for storing and transmitting various information.

In particular, in order to increase the performance of a storage medium such as a hard disk, the coercive force, which is the strength of the magnetic field required to make the magnetization rate "0", must be high. Therefore, various attempts have been made to increase the coercive force of the magnetic body.

In this regard, the ε-Fe ₂ O ₃ phase in the iron oxide crystal phase included in the ferri-magnetic material has been expected to provide a high coercive force, but the ε-Fe ₂ O ₃ phase is inherently unstable, so α-Fe ₂ O ₃ and Since the phase is rapidly converted to γ-Fe ₂ O ₃ , it is still a difficult task to prepare a magnetic body stably containing the ε-Fe ₂ O ₃ phase.

In order to solve the above problems, a method for preparing nanoparticles having an ε-Fe ₂ O ₃ phase using a silica gel matrix has been reported, but the reaction conditions and manufacturing process are necessary in that a medium such as a silica gel matrix is required. There are limitations of being tricky

Therefore, there is still a need for a magnetic material having a high coercive force including an ε-Fe ₂ O ₃ phase without a medium and a method for manufacturing the same.

According to one aspect, to provide a magnetic material having a high coercive force including an ε-Fe ₂ O ₃ phase without a medium and a method for manufacturing the same.

According to one aspect, there is provided a magnetic body comprising a ε-Fe ₂ O ₃ phase that does not include the Y ₃ Fe ₅ O ₁₂ phase, which is prepared by heat-treating a mixture powder of a yttrium precursor and an iron precursor.

According to one embodiment, the heat treatment is a single heat treatment.

According to one embodiment, the heat treatment includes firing the mixture at 850°C.

According to one embodiment, the heat treatment is heated to 850°C at a rate of 7 to 8°C/min from 20°C in an oxygen atmosphere, and then maintained at 850°C for 120 minutes, and a rate of -7 to -8°C/min It is carried out by a method of reducing the temperature to 20°C.

According to one embodiment, the magnetic material has a plurality of peaks from 200 cm ^-1 to 650 cm ^-1 in Raman spectroscopy.

According to one embodiment, the magnetic material has a coercive force (Hc) value of 17 kOe or more.

A magnetic material prepared by heat-treating a mixture powder of a yttrium precursor and an iron precursor according to one aspect includes an ε-Fe ₂ O ₃ phase, but does not include a Y ₃ Fe ₅ O ₁₂ phase, and has a high coercive force (Hc) value of 17 kOe or more Have

1 is a Raman spectrum for the magnetic material of Example 1.
2 is XRD data for Example 1 and Comparative Example 1.
3 is a hysteresis curve for Example 1 and Comparative Example 1.

The present inventive concept described below may apply various transformations and may have various embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit this creative idea to a specific embodiment, and it should be understood to include all conversions, equivalents, or substitutes included in the technical scope of the creative idea.

The terms used below are only used to describe specific embodiments and are not intended to limit the creative ideas. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the following, the terms "comprises" or "have" are intended to indicate the presence of features, numbers, steps, acts, components, parts, components, materials or combinations thereof described in the specification, one or more thereof. It should be understood that the above other features, numbers, steps, operations, components, parts, components, materials or combinations thereof are not excluded in advance. "/" used below may be interpreted as "and" or "or" depending on the situation.

According to one aspect, there is provided a magnetic body comprising a ε-Fe ₂ O ₃ phase that does not include the Y ₃ Fe ₅ O ₁₂ phase, which is prepared by heat-treating a mixture powder of a yttrium precursor and an iron precursor.

Among ferromagnetic materials having high magnetic properties, ferrimagnetic materials are based on iron oxide. Among various crystal phases included in the ferrimagnetic material, the ε-Fe ₂ O ₃ phase is known as a phase that provides a high coercive force to the magnetic material. However, the ε-Fe ₂ O ₃ phase includes highly unstable general, immediately formed a stable form of α-Fe ₂ O ₃ phase and a γ-Fe ₂ since the switch to the O ₃ phase, ε-Fe ₂ O ₃ phase is Obtaining the containing magnetic body has been considered as one of the very difficult tasks.

In this connection, there have been reported various techniques for forming ε-Fe ₂ O ₃ phase in the matrix in order to maintain the ε-Fe ₂ O ₃ phase. As a representative example, a method of forming nanoparticles having an ε-Fe ₂ O ₃ phase in pores of a silicon-based matrix is known. However, since nanoparticles having an ε-Fe ₂ O ₃ phase have very low surface energy, it is difficult to prevent phase conversion to α-Fe ₂ O ₃ phase and γ-Fe ₂ O ₃ phase when increasing the particle size. This still exists. In addition, since a silicon matrix is used as an essential component, a separate process for separating nanoparticles having an ε-Fe ₂ O ₃ phase is required, and thus there is still a need for improvement in complexity in the manufacturing process.

In contrast, a magnetic material prepared according to one aspect and not including the Y ₃ Fe ₅ O ₁₂ phase and the ε-Fe ₂ O ₃ phase does not use a mediator such as a silicon matrix, a yttrium precursor and an iron precursor It contains ε-Fe ₂ O ₃ phase by a simple process of mixing and single heat treatment, and has a high coercive force. On the other hand, when additional heat treatment is performed on the magnetic body manufactured according to one aspect, since the coercive force decreases as the ε-Fe ₂ O ₃ phase is converted to the Y ₃ Fe ₅ O ₁₂ phase, a single heat treatment is very important. By having high coercive force, it is possible to maintain high magnetic properties even when the external magnetic field is zero. As a result, it is applied in electric and electronic applications closely related to real life, such as household electrical equipment, iron cores for transmission transformers, communication equipment, and memory devices of high-speed computer This is possible.

The yttrium precursor may be selected from yttrium nitride, oxide, carbide, chloride, sulfide, or hydroxide. For example, the yttrium precursor is yttrium nitrate.

The iron precursor may be selected from iron nitride, oxide, carbide, chloride, sulfide, or hydroxide. For example, the iron precursor is iron nitrate.

The mixture powder of the yttrium precursor and the iron precursor may be prepared by drying from an aqueous mixture solution mixed in an acidic solution. The acidic solution is an aqueous solution of pH 1. The acidic solution may be an aqueous citric acid solution.

The mixture powder of the yttrium precursor and the iron precursor can be obtained by heating and drying the aqueous mixture solution at a temperature of 100°C or higher. Heating and drying can be performed by heating the aqueous solution itself, or in an oven.

Before the heat treatment of the mixture powder, the step of grinding the mixture powder into particulate powder may be further performed. The grinding process may be performed by a mechanical grinding method. For example, the crushing process may be performed by ball milling or agate triggering. The mechanical grinding method is performed until the density of the fine particle powder calculated by the Archimedes method below becomes 95% or more.

In addition, the pulverized mixture fine powder as described above may be subjected to a further step of sintering prior to heat treatment. By subjecting the mixture fine particle powder to heat treatment, uniform heat can be transferred to the fine particle powder, and as a result, a magnetic body having a high coercive force including the desired ε-Fe ₂ O ₃ phase can be obtained. However, when the mixture fine powder is heat-treated in a bulk state without being subdivided, the heat transfer rates inside and outside the fine particle powder simple substance are different, and as a result, a magnetic body having sufficient coercive force cannot be obtained. The subdivision may be placed in a container used for heat treatment, for example, in the bottom of the crucible, in the amount of 30% by volume or less of the total volume of the crucible.

For example, it may be subdivided in an amount arranged to have a height of 15 mm or less based on a crucible of 50 mm height, and may be, for example, 3.7 g to 4.0 g.

The heat treatment is carried out in an oxygen atmosphere at room temperature, for example, from 20°C to 850°C at a rate of 7 to 8°C/min, maintained at 850°C for 120 minutes, and at a rate of -7 to -8°C/min. It is carried out by a method of reducing the temperature to 20°C. The gentle temperature increase and temperature reduction rate suppress the rapid growth of crystals, contribute to the stable formation of ε-Fe ₂ O ₃ phase, and stable crystal growth through heat treatment at 850°C.

The magnetic material according to one embodiment obtained a Raman spectrum of the magnetic material as shown in FIG. 1 by Raman spectroscopy. Referring to Figure 1, the magnetic body has a plurality of peaks from 200 cm ^-1 to 650 cm ^-1 . This peak proves that the magnetic body contains an ε-Fe ₂ O ₃ phase.

The present invention is described in more detail through the following examples and comparative examples. However, the examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example 1

(Production of citric acid)

Citric acid (C ₆ H ₈ O _{7 ㆍ} H ₂ O) (purchased from Sigma-Aldrich) 9.222 g was added in 200 ml of distilled water (DIwater) and stirred at 300 K at a stirring speed of 300 rpm for 20 hours to prepare a citric acid aqueous solution. . The obtained aqueous solution of citric acid had a pH of 1.

(Manufacturing of magnetic material)

Yttrium(III) nitratehexahydrate (Sigma-Aldrich product number 237957-500G) 6.950g and Iron(III)nitratenonahydrate (Sigma-Aldrich product number 216828-100G) 12.120g were added to 200 ml of the citric acid aqueous solution prepared above and 24 at 80°C. The mixture was stirred with time to prepare a mixed solution having a concentration of 0.48 mol.

The mixture solution prepared above was heated at a temperature of 100° C. or higher to obtain a mixture powder from which solvent and moisture were removed.

The mixture powder was subjected to a mechanical grinding operation using an agate trigger and a mesh. The mechanical grinding operation was performed until the density of the pulverized mixture powder became 95% or more according to the calculation by the Archimedes method.

3.7004 g of the pulverized mixture was fractionated and placed in a crucible.

The pulverized mixture powder placed in the crucible was heat-treated under an oxygen atmosphere at room temperature (20° C.) until it reached 850° C. at a rate of 7.5° C./min (about 110 minutes), and thereafter 120 at 850° C. Heat treatment was performed for a minute. Thereafter, heat treatment was carried out while reducing the temperature at a rate of -7.5°C/min until it reached room temperature (about 110 minutes) to obtain a magnetic body containing red desired ε-Fe ₂ O ₃ .

Comparative Example 1

The magnetic body obtained in Example 1 was subjected to an additional heat treatment at 1400° C. to obtain a material having a composition of Y ₃ Fe ₅ O ₁₂ .

(Evaluation example)

XRD evaluation

XRD evaluation was performed on the materials obtained in Example 1 and Comparative Example 1, and the XRD evaluation results are shown in FIG. 2. In FIG. 2, #43-0507 is the XRD pattern of Y3Fe5O12, #39-1346 is the XRD pattern of γ-Fe ₂ O ₃ crystals, #16-0653 is the XRD pattern of ε-Fe ₂ O ₃ crystals, and #33 -0664 is the XRD pattern of the α-Fe ₂ O ₃ crystal.

Referring to Figure 2, it can be seen that the material obtained in Comparative Example 1 coincides with the reference XRD peak of the Y ₃ Fe ₅ O ₁₂ material, which is a ferrimagnetic material. In contrast, it can be seen that the magnetic material obtained in Example 1 does not match the reference XRD peak of the Y ₃ Fe ₅ O ₁₂ material, and thus has different crystals from Y ₃ Fe ₅ O ₁₂ .

These results are thought to form Y ₃ Fe ₅ O ₁₂ , which is a new type of crystal, by rapid growth and fusion of crystals in a high temperature heat treatment process at 1400°C.

In addition, it can be confirmed that the magnetic body obtained in Example 1 includes an XRD pattern for ε-Fe ₂ O ₃ crystals.

Coercivity evaluation

The coercive force of the materials obtained in Example 1 and Comparative Example 1 was measured, and the results are shown in Table 1 and FIGS. 3(a) and 3(b), respectively.

Heat treatment temperature M _s (emu/g) M _r (emu/g) H _c (Oe) Example 1 1.650 0.702 18917 Comparative Example 1 28.162 2.019 56

Referring to Table 1 and FIGS. 3(a) and 3(b), in the case of a magnetic material subjected to a single heat treatment at 850° C., a coercive force approximately 335 times greater than that of a material subjected to an additional heat treatment at 1400° C. You can see it has.

The difference in the coercive force values is considered to be due to the presence of the ε-Fe ₂ O ₃ phase in the magnetic material. In contrast, in the case of the magnetic material of Comparative Example 1 heat-treated twice, the ε-Fe ₂ O ₃ phase is transferred to the Y ₃ Fe ₅ O ₁₂ crystal phase, so that the coercive force value is considered to have a value close to zero.

Raman spectrum evaluation (ε- Fe ₂ O ₃ of Existence check)

The Raman spectrum of the magnetic body obtained in Example 1 was obtained by Raman spectroscopy. The results are shown in FIG. 1.

Referring to FIG. 1, a plurality of peaks at 200 cm ^-1 to 650 cm ^-1 and peaks at 1300 cm ^-1 are observed. The multiple peaks from 200 cm ^-1 to 650 cm ^-1 correspond to the intrinsic peaks by continuous oscillating motion on the ε-Fe ₂ O ₃ phase. Therefore, it can be confirmed that the magnetic body obtained in Example 1 contains the ε-Fe ₂ O ₃ phase.

In the above, a preferred embodiment according to the present invention has been described with reference to the drawings and examples, but this is merely exemplary, and various modifications and equivalent other implementations are possible from those skilled in the art. Will be able to understand. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims (7)

A magnetic material containing ε-Fe ₂ O ₃ phase without Y ₃ Fe ₅ O ₁₂ phase prepared by heat-treating the mixture powder of yttrium precursor and iron precursor. According to claim 1,
The heat treatment is a single heat treatment, a magnetic body. According to claim 1,
The heat treatment includes baking the mixture at 850° C., a magnetic body. According to claim 1,
The heat treatment, after heating up to 850 °C at a rate of 7 to 8 °C / min, maintained at 850 °C for 120 minutes, and reduced to room temperature at a rate of -7 to -8 °C / min, magnetic material. According to claim 1,
Before the heat treatment, further comprising sintering the mixture powder, a magnetic body. According to claim 1,
The magnetic material has a plurality of peaks from 200 cm ^-1 to 650 cm ^-1 in Raman spectroscopy. According to claim 1,
The magnetic material has a coercive force (Hc) value of 17 kOe or more.

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