Electromagnetic wave absorbing composition and electromagnetic wave absorber

Abstract

An electromagnetic wave absorption composition and an electromagnetic wave absorber are disclosed. The disclosed electromagnetic wave absorbing composition may be composed of: a main component containing iron oxide (FexOy, x=1, 2, 3, and y=1, 3, 4) in a content of 38 mol% to 52 mol%, manganese oxide (MnxOy, x=1, 2, 3, and y=1, 3, 4, 7) in a content of 18 mol% to 40 mol%, and zinc oxide (ZNO) in a content of 14 mol% to 30 mol%; a sub-component containing copper oxide (CuxOy, x=1, 2, and y=1, 2, 3) in a content of 1 mol% to 4 mol% and cobalt oxide (CoxOy, x=1, 2, 3, and y=1, 3, 4) as a remainder; and an additive including a simple substance or a compound containing sodium (Na) in a content of 10 ppm to 200 ppm.

Description

Electromagnetic wave absorption composition and electromagnetic wave absorber

[0001] The present invention relates to electromagnetic wave absorption technology, and more specifically, to an electromagnetic wave absorption composition and an electromagnetic wave absorber.

[0002] With the advancement of electronic and information and communication devices, the operating frequency of circuits is increasing to high-frequency bands ranging from several to tens of MHz, and there is a trend toward the multifunctionality, miniaturization, and portability of electronic devices. Various problems can arise, such as device malfunctions and signal quality degradation caused by electromagnetic interference or noise between these devices, as well as harm to the human body due to electromagnetic radiation. Consequently, the suppression of unnecessary radio waves is required, and to address this, the demand for electromagnetic absorbers is rising. Furthermore, due to the increase in electronic circuits and components resulting from the advanced electrification of automobiles and electronic products, regulations regarding electromagnetic noise generated in daily life are being required. To regulate the aforementioned electromagnetic noise, the CISPR 36 standard, which evolved from the CISPR 25 standard, has been established to standardize evaluation and measurement methods for test sites at frequencies below 30 MHz. Accordingly, there is an increasing demand for anechoic chambers capable of measuring electromagnetic noise at low frequencies below 30 MHz.

[0003] In addition to being used as a wall material for a radio wave anechoic chamber, preventing antenna signal interference and increasing signal range for smartphones, the above-mentioned radio wave absorber can also be wound around wires and used as a ferrite core for a low-pass filter.

[0004] Furthermore, the materials used for these electromagnetic wave absorbers include sintered ferrites. For instance, Mn-Zn ferrites and Ni-Zn ferrites have been developed as materials for electromagnetic wave absorbers. However, manufacturing costs for Ni-Zn ferrite absorbers can increase due to the high cost of nickel (Ni). On the other hand, compared to Ni-Zn ferrite absorbers, Mn-Zn ferrite absorbers are cheaper and can exhibit excellent reflection attenuation characteristics while remaining thin. Consequently, Mn-Zn ferrite absorbers are gaining attention as they can be manufactured at a lower cost than Ni-Zn ferrite absorbers. However, while Mn-Zn ferrites satisfy the required characteristics of electromagnetic wave absorbers by adding small amounts of rare metals, there are risk factors such as supply instability and price surges caused by the recent weaponization of rare metals by countries like the United States and China to control their exports.

[0005] Meanwhile, when the above-mentioned electromagnetic wave absorber is used as an inner wall for an electromagnetic anechoic chamber, processing is required because a certain level of dimensional precision is necessary; however, chips may be generated during processing or installation. Since these chips are a factor that leads to increased costs due to reduced yield, the electromagnetic wave absorber is required to have chipping resistance.

[0006] In order to improve this, calcium oxide (CaO) and vanadium pentoxide (V2O5) are conventionally used as additives in Mn-Zn ferrites. However, if a large amount of CaO is used, a liquid phase is formed at the grain boundaries during the firing of the absorber, causing excessive grain growth and potentially lowering the flexural strength. When the strength of the Mn-Zn ferrite is low, it is prone to breakage during machining or assembly of the fired body. This not only lowers the firing yield but also poses a risk of breakage due to low toughness, making it difficult to use as an electromagnetic wave absorber for anechoic chambers.

[0007] Therefore, there is a need to develop an electromagnetic wave absorbing composition and an electromagnetic wave absorber having excellent chipping resistance and flexural strength while limiting the content of rare metals, CaO, and V2O5 used in the electromagnetic wave absorber.

[0008] The technical problem that the present invention aims to solve is to provide an electromagnetic wave absorbing composition that is capable of low-cost manufacturing while limiting the content of rare metals, CaO, and V2O5, and possesses excellent chipping resistance, fracture toughness, and flexural strength.

[0009] In addition, the invention provides an electromagnetic wave absorbing composition that enables stable sintering even when sintering large molded bodies by making it possible to increase sinterability.

[0010] In addition, the invention provides an electromagnetic wave absorber having a low reflection coefficient (high absorption performance) even in the low frequency band.

[0011] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be understood by those skilled in the art from the description below.

[0012] According to one embodiment of the present invention, iron oxide (Fe) having a content of 38 mol% to 52 mol% x O y , x=1, 2, 3, y=1, 3, 4), manganese oxide (Mn) having a content of 18 mol% to 40 mol% x O y A main component comprising zinc oxide (ZnO) having a content of 14 mol% to 30 mol% and x=1, 2, 3, y=1, 3, 4, 7); and copper oxide (Cu) having a content of 1 mol% to 4 mol%. x O y x=1, 2, y=1, 2, 3) and the remainder cobalt oxide (Co x O yAn electromagnetic wave absorbing composition may be provided, comprising an auxiliary component including , x=1, 2, 3, y=1, 3, 4); and an additive including a single element or compound including sodium (Na) having a content of 10 ppm to 2000 ppm.

[0013] The above additive may further include a component or compound containing a transition metal or alkaline earth metal having a content of several hundred ppm or less.

[0014] In one embodiment, the element or compound containing the alkaline earth metal contains calcium oxide (CaO), and the element or compound containing the transition metal contains vanadium pentoxide (V2O5), and the total content of the calcium oxide (CaO) and the vanadium pentoxide (V2O5) may be 300 ppm or less.

[0015] According to another embodiment of the present invention, an electromagnetic wave absorber composed of the described electromagnetic wave absorbing composition may be provided.

[0016] The matching thickness of the electromagnetic wave absorber is in the range of 4 mm to 10 mm, and the reflection coefficient of the electromagnetic wave absorber may be -18 dB or less at 10 MHz. The reflection coefficient of the electromagnetic wave absorber is -22 dB or less at 30 MHz.

[0017] According to another embodiment of the present invention, iron oxide (Fe) having a content of 38 mol% to 52 mol% x O y , x=1, 2, 3, y=1, 3, 4), manganese oxide (Mn) having a content of 18 mol% to 40 mol% x O y , x=1, 2, 3, y=1, 3, 4, 7) and first raw material powders of the main component comprising zinc oxide (ZnO) having a content of 14 mol% to 30 mol%, and copper oxide (Cu) having a content of 1 mol% to 4 mol%. x O yx=1, 2, y=1, 2, 3) and the remainder cobalt oxide (Co x O y A method for manufacturing an electromagnetic wave absorber may be provided, comprising the steps of: preparing a second raw material powder of a minor component including x=1, 2, 3, y=1, 3, 4); and preparing an additive including a single component or compound including sodium (Na) having a content of 10 ppm to 2000 ppm; mixing the first raw material powder, the second raw material powder, and the additive; and molding the mixture to form a molded body.

[0018] In one embodiment, the step of forming a molded body by molding the mixture may include the step of heat-treating the mixture to produce intermediate particles; the step of wet-grinding the intermediate particles; the step of mixing the ground intermediate particles with a solvent to form pellets; and the step of compressing the pellets to form a molded body. The step of drying the ground intermediate particles may be further included.

[0019] In one embodiment, the additive may further include a component or compound containing a transition metal or alkaline earth metal having a content of several hundred ppm or less. The component or compound containing the alkaline earth metal may contain calcium oxide (CaO), and the component or compound containing the transition metal may contain vanadium pentoxide (V2O5), and the total content of the calcium oxide (CaO) and the vanadium pentoxide (V2O5) may be 300 ppm or less.

[0020] According to an embodiment of the present invention, an electromagnetic wave absorbing composition has an iron oxide (Fe) content of 38 mol% to 52 mol%. x O y , x=1, 2, 3, y=1, 3, 4), manganese oxide (Mn) having a content of 18 mol% to 40 mol% x O y, x=1, 2, 3, y=1, 3, 4, 7) and zinc oxide (ZnO) having a content of 14 mol% to 30 mol%, copper oxide (Cu) having a content of 1 mol% to 4 mol% x O y By being composed of an additive comprising a single element or compound containing x=1, 2, y=1, 2, 3), the remainder being cobalt oxide (CoxOy, x=1, 2, 3, y=1, 3, 4) and sodium (Na) having a content of 10 ppm to 2000 ppm, it is possible to provide an electromagnetic wave absorbing composition that has excellent chipping resistance, fracture toughness, and flexural strength while limiting the content of rare metals, CaO, and V2O5, and enabling low-cost manufacturing.

[0021] In addition, it is possible to increase sinterability, thereby providing an electromagnetic wave absorbing composition that enables stable sintering even when sintering large molded bodies.

[0022] In addition, it is possible to provide an electromagnetic wave absorber having a low reflection coefficient (high absorption performance) even in the low frequency band.

[0023] However, the effects of the present invention are not limited to the above effects and can be extended in various ways without departing from the technical concept and scope of the present invention.

[0024] FIG. 1 is a graph showing the composition ratio and reflection coefficient in the electromagnetic wave absorbing compositions of Examples 1 to 5 and Comparative Examples 1 to 3.

[0025] FIG. 2 is a graph showing the composition ratio and reflection coefficient in the electromagnetic wave absorbing compositions of Examples 6 to 9 and Comparative Examples 4 and 5.

[0026] FIG. 3 is a graph showing the composition ratio, reflection coefficient, and bending strength in the electromagnetic wave absorbing compositions of Examples 10 to 12 and Comparative Examples 6 and 7.

[0027] Figure 4 is a graph showing the absorption performance of the electromagnetic wave absorbing compositions of Example 9 and Comparative Example 5.

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0029] The embodiments of the present invention described below are provided to more clearly explain the present invention to those skilled in the art, and the scope of the present invention is not limited by the following embodiments, and the following embodiments may be modified in various other forms.

[0030] The terms used herein are for describing specific embodiments and are not intended to limit the invention. Terms used herein in the singular form may include plural forms unless the context clearly indicates otherwise. Additionally, the terms “comprise” and / or “comprising” used herein specify the presence of the mentioned features, steps, numbers, actions, components, elements, and / or groups thereof, and do not exclude the presence or addition of one or more other features, steps, numbers, actions, components, elements, and / or groups thereof. Furthermore, the term “connected” used herein means not only that components are directly connected, but also includes the concept of indirectly connecting components through the interposition of additional components between them.

[0031] Furthermore, when a component is described in this specification as being located "on" another component, this includes not only cases where a component is in contact with another component, but also cases where another component exists between the two components. The term "and / or" as used in this specification includes any one of the listed items and all combinations of one or more thereof. Additionally, terms of degree such as "about" and "substantially" as used in this specification are used to mean a range of numerical values ​​or degrees or approximate values, taking into account inherent manufacturing and material tolerances, and are used to prevent an infringer from unfairly exploiting the disclosures in which precise or absolute figures provided to aid in understanding this specification are mentioned.

[0032] Embodiments of the present invention will be described in detail below with reference to the attached drawings. The sizes or thicknesses of the areas or parts depicted in the attached drawings may be slightly exaggerated for the clarity of the specification and convenience of explanation. Throughout the detailed description, the same reference numerals indicate the same components.

[0033] The electromagnetic wave absorbing composition of the present invention is an Mn-Zn ferrite, and as a main component, iron oxide (Fe x O y , x=1, 2, 3, y=1, 3, 4), manganese oxide (Mn x O y It contains , x=1, 2, 3, y=1, 3, 4, 7) and zinc oxide (ZnO), and as a minor component, copper oxide (Cu x O y , x=1, 2, y=1, 2, 3) and cobalt oxide (Co x O y, x=1, 2, 3, y=1, 3, 4) and may include an element or compound containing sodium (Na) as an additive. The iron oxide is a compound of iron and oxygen and may include any one of FeO, Fe2O3 (tri-ferrous oxide) or Fe3O4 (tetra-ferrous oxide); the manganese oxide may include any one of MnO, Mn2O3, Mn3O4, or Mn2O7; the copper oxide may include any one of CuO, Cu2O, Cu2O3, or CuO2; and the cobalt oxide may include any one of CoO, Co2O3, and Co3O4. Non-limitingly, the element or compound containing sodium (Na) may be sodium oxide (Na2O).

[0034] The above main component is iron oxide (Fe) having a content of 38 mol% to 52 mol%. x O y , x=1, 2, 3, y=1, 3, 4), manganese oxide (Mn) having a content of 18 mol% to 40 mol% x O y It may be composed of ) and zinc oxide (ZnO) having a content of 14 mol% to 30 mol%. Preferably, the manganese oxide (Mn x O y ) has a content of 21 mol% to 35 mol%. The above auxiliary component is copper oxide (Cu) having a content of 1 mol% to 4 mol%. x O y x=1, 2, y=1, 2, 3) and the remainder cobalt oxide (Co x O y It may include x=1, 2, 3, y=1, 3, 4). The additive may include a single element or a compound containing the element sodium (Na) having a content of 10 ppm to 2000 ppm. Here, 1 ppm = 0.0001 wt%.

[0035] The critical significance of the numerical limitation of each oxide composition constituting the electromagnetic wave absorbing composition is as follows.

[0036] (Fe x O y : 38.0 mol% to 52.0 mol%

[0037] Fe x O y If this is less than 38.0 mol%, T c The Curie temperature (or Curie point) decreases, making it impractical for use as an electromagnetic wave absorber. In other words, if the Curie temperature is significantly low, the temperature of the absorber itself easily exceeds the Curie temperature due to converted heat, leading to a problem where it loses its magnetism and fails to function as an electromagnetic wave absorber. On the other hand, Fe x O y If this exceeds 52.0 mol%, the resistivity of the material decreases and the dielectric constant increases, which may weaken the electromagnetic wave absorption performance. The above Curie temperature refers to the transition temperature at which a ferromagnetic material changes from a ferromagnetic state to a paramagnetic state or vice versa. If a ferromagnetic material, such as a magnet, is heated above the Curie temperature, it may lose its magnetic properties.

[0038] (Mn x O y : 18 mol% to 40 mol%

[0039] Manganese oxide (Mn x O y ) can satisfy reflection characteristics such that the reflection coefficient is -18dB or less at 10MHz to 30MHz, or -22dB or less at 30MHz, within the range of 18 mol% to 40 mol%. Manganese oxide (Mn x O y If the content of ) falls outside the range of 18 mol% to 40 mol%, the reflection properties decrease, making it difficult to satisfy the required reflection properties.

[0040] (ZnO: 14 mol% to 30 mol%)

[0041] If ZnO is less than 14 mol %, T c As the amount increases, the real part of μ' (complex permeability) increases, and the electromagnetic wave absorption performance may be weakened. On the other hand, when the amount of ZnO exceeds 30 mol %, the imaginary part of μ' (complex permeability) decreases, so it becomes impossible to obtain a sufficient electromagnetic wave absorption effect.

[0042] (Cu x O y : 1 mol% to 4 mol%

[0043] Copper oxide (Cu x O y If the content of ) falls outside the range of 1 mol% to 4 mol%, the electromagnetic wave absorption performance may be weakened.

[0044] (Co x O y : Remaining part (residual)

[0045] Fe x O y , Mn x O y , ZnO, Cu x O y and Co x O y To make the total amount of 100 mol%, the previously described Fe x O y , Mn x O y , ZnO, Cu x O y As the remainder part according to each prescribed amount of Co x O y It can contain.

[0046] By including each subcomponent within the above numerical range, it is possible to obtain a good reflection coefficient of -22dB or less at room temperature (15 to 25℃). If the content of either subcomponent is less than the above lower limit, this effect cannot be obtained. On the other hand, if the content of either subcomponent exceeds the above upper limit, the crystal grain size becomes fine and the soft magnetic properties may be weakened.

[0047] In one embodiment, the additive may further include a single element or compound containing a transition metal having a content of hundreds of ppm or less. The transition metal of the additive may be different from the transition metal included in the main component and the minor component. The transition metal element may include at least one of a fourth-period transition element (3d element) including Sc to Cu, a fifth-period transition element (4d element) including Y to Ag, a sixth-period transition element (5d, 4f element) including La to Au, and a seventh-period transition element (5f element) including Ac to Lr.

[0048] Alternatively, the additive may further include a component or compound containing an alkaline earth metal having a content of several hundred ppm or less. Specifically, the component or compound containing the alkaline earth metal may contain calcium oxide (CaO), and the component or compound containing the transition metal may contain vanadium pentoxide (V2O5). The total content of the calcium oxide (CaO) and the vanadium pentoxide (V2O5) may be 300 ppm or less.

[0049] (CaO + V2O5: 300 ppm or less)

[0050] By keeping the total amount of CaO and V2O5 within the above numerical range, it becomes possible to suppress the occurrence of chipping. If the total amount exceeds the above upper limit, the structure becomes such that grain boundary fracture proceeds abnormally due to an increase in grain boundary thickness and grain refinement, which may reduce the fracture toughness and flexural strength of the electromagnetic wave absorbing material.

[0051] (Na2O: 10 ppm to 2000 ppm)

[0052] By including Na2O within the above numerical range, it is possible to improve the reflection coefficient performance in the low frequency band. Specifically, it is possible to improve properties by increasing the permeability (μ') through controlling the size of the crystal grains within the sintered body. If the content of Na2O is below the above lower limit, this effect cannot be obtained. On the other hand, if the content of Na2O exceeds the above upper limit, the growth of the crystal grains becomes non-uniform and proceeds excessively, i.e., abnormal grain growth occurs, which may lead to a weakening of soft magnetic properties and a decrease in mechanical strength.

[0053] Meanwhile, since the content of each component and additive described above in the present invention is very small, there is no problem with strength or humidity stability similar to that of an electromagnetic wave absorber of Mn-Zn ferrite, and a radio wave absorbing material having high strength and humidity stability can be obtained.

[0054] Next, we will describe the results of preparing various examples and comparative examples of radio wave absorbing compositions with varying compositional ratios of each oxide, and measuring the performance (reflection coefficient) of radio wave absorbers using the prepared compositions. The preparation conditions of the radio wave absorbing compositions and the measurement conditions of the performance (reflection coefficient) in these examples and comparative examples were as follows.

[0055] Finally, the raw powders were mixed to achieve the compositional ratio described below, and calcined in air at approximately 600°C to 1000°C for about 2 to 4 hours. The obtained calcined powder was wet-milled using a ball mill and then dried. After drying, a small amount of solvent (e.g., water, acetone, alcohol) was added to the powder to form granules, and the granules (or pellets) were formed onto a disc of a predetermined diameter and thickness at a volume of approximately 1 to 2 ton / cm² 2A molded body was formed. The molded body was heated in air to 1000°C to 1500°C at a rate of approximately 100 to 200°C per hour or less and maintained for approximately 3 hours. Afterward, the atmosphere was switched to nitrogen, and the temperature was lowered to room temperature at a rate of approximately 200°C per hour or less. Subsequently, a test specimen was cut into a ring shape from the obtained plate-shaped sintered body, and the impedance of the test specimen was measured using a network analyzer. The test specimen was machined into a ring shape with an outer diameter of 39 mm and an inner diameter of 17 mm, and the measurement was performed at 6.7 mm. If the matching thickness was 6.7 mm or less, the test specimen was machined to match the matching thickness and measured; if the matching thickness was 6.7 mm or more, the specimen was machined to 6.7 mm and measured using a network analyzer to obtain the value. The reflection coefficient for electromagnetic waves was measured using a network analyzer in the range of 10 MHz to 30 MHz.

[0056] FIG. 1 is a graph showing the composition ratios of the radio wave absorbing compositions of Examples 1 to 5 and Comparative Examples 1 to 3, and the reflection coefficients for radio waves of 10 MHz and 30 MHz that were measured.

[0057] Referring to FIG. 1, Examples 1 to 5 of the electromagnetic wave absorbing composition have different compositional ratios of Fe2O3, MnO, ZnO, CuO, and CoO within an effective range, while Comparative Examples 1 to 3 have different compositional ratios of Fe2O3, MnO, ZnO, CuO, and CoO such that at least one of them falls outside the effective range. The compositional ratio of Na2O in the electromagnetic wave absorbing composition was fixed at 0.05 within the effective range. In Examples 1 to 5, which satisfy the compositional ratios of the components constituting the electromagnetic wave absorbing composition, a reflection coefficient of -18 dB or less at 10 MHz and -22 dB or less at 30 MHz can be achieved in all of them. On the other hand, in Comparative Examples 1 to 3, where at least one of the compositional ratios of Fe2O3, MnO, ZnO, CuO, and CoO falls outside the effective range, a reflection coefficient of -18 dB or less at 10 MHz and -22 dB or less at 30 MHz could not be achieved. The reason for this decrease in electromagnetic wave absorption performance appears to be due to a reduction in the material's resistivity and an increase in dielectric constant.

[0058] FIG. 2 is a graph showing the composition ratios of the electromagnetic wave absorbing compositions of Examples 6 to 9 and Comparative Examples 4 and 5, and the reflection coefficients for electromagnetic waves of 10 MHz and 30 MHz that were measured.

[0059] Referring to FIG. 2, Examples 6 to 8 and Comparative Examples 4 to 5 of these had different compositional ratios of Fe2O3, MnO, ZnO, CuO, and CoO constituting the electromagnetic wave absorbing composition within an effective range. Then, while increasing the compositional ratio of Na2O constituting the electromagnetic wave absorbing composition, the reflection coefficients were measured at 10 MHz and 30 MHz, respectively.

[0060] In Examples 6 to 9, which satisfy the composition ratio of the components constituting the electromagnetic wave absorbing composition, reflection coefficients of -18dB or less and -22dB or less were achieved at 10MHz and 30MHz, respectively. However, in Comparative Examples 4 and 5, where the composition ratio of Na2O falls outside the effective range, it can be observed that the reflection coefficient decreases at 10MHz and 30MHz. This appears to be because the amount of NaOH increases excessively, leading to a decrease in electromagnetic wave absorption performance. It can be seen that increasing the composition ratio of Na2O within the effective range improves electromagnetic wave absorption performance at 10MHz to 30MHz.

[0061] FIG. 3 is a graph showing the composition ratio, reflection coefficient, and bending strength in the electromagnetic wave absorbing compositions of Examples 9 to 11 and Comparative Examples 6 and 7.

[0062] Referring to FIG. 3, Examples 10 to 12 and Comparative Examples 6 and 7 of these compositions had different compositional ratios of Fe2O3, MnO, ZnO, CuO, CoO, and Na2O within an effective range for constituting the electromagnetic wave absorbing composition. Here, to increase the flexural strength of the electromagnetic wave absorber, the reflection coefficient and flexural strength were measured at 10 MHz and 30 MHz, respectively, while increasing the amounts of CaO and V2O5.

[0063] In Examples 10 to 12, which satisfy the composition ratio of the components constituting the electromagnetic wave absorbing composition, it can be seen that in all of them, the reflection coefficients at 10 MHz and 30 MHz are -18 dB or less and -22 dB or less, respectively, while maintaining improved flexural strength. However, looking at Comparative Examples 6 and 7, where the total content of CaO and V2O5 falls outside the effective range, it can be confirmed that although the flexural strength increases when CaO and V2O5 are increased, the characteristics of the reflection coefficient at 10 MHz and 30 MHz deteriorate. In other words, it can be seen that while adjusting the composition ratio of CaO and V2O5 increases the flexural strength, if the total content of the composition ratio of CaO and V2O5 exceeds 300 ppm wt%, the reflection coefficient decreases at 10 MHz and 30 MHz.

[0064] Figure 4 is a graph showing the absorption performance of the electromagnetic wave absorbing compositions of Example 9 and Comparative Example 5. The X-axis is the frequency band, and the y-axis is the reflection coefficient.

[0065] Referring to FIG. 4, in the frequency band of about 80 MHz or lower, the reflection coefficient of Example 9 was lower than that of Comparative Example 5, and in the frequency band of about 400 MHz or higher, the reflection coefficients of Comparative Example 5 and Example 9 were nearly similar. However, in the range of 80 MHz to 400 MHz, the reflection coefficient of Comparative Example 5 was lower than that of Example 9. Preferably, the present invention can achieve a reflection coefficient of -18 dB or less at 10 MHz and -22 dB or less at 30 MHz.

[0066] The effects of the present invention are clear from the experimental results above. That is, the present invention is an electromagnetic wave absorber composed of an Mn-Zn ferrite sintered body, wherein the electromagnetic wave absorber contains iron oxide (Fe₂O₃) having a content of 38 mol% to 52 mol%. x O y, x=1, 2, 3, y=1, 3, 4), manganese oxide (Mn) having a content of 18 mol% to 40 mol% x O y A main component comprising a main component including zinc oxide (ZnO) having a content of 14 mol% to 30 mol% and , x=1, 2, 3, y=1, 3, 4, 7), and copper oxide (Cu) having a content of 1 mol% to 4 mol% x O y x=1, 2, y=1, 2, 3) and the remainder cobalt oxide (Co x O y Since it is configured to have a minor component including , x=1, 2, 3, y=1, 3, 4), and to contain a predetermined amount of an additive including a compound or a component containing sodium (Na) having a content of 10 ppm to 2000 ppm with respect to 100 parts by weight of the main component and the minor component, it is possible to reduce manufacturing costs while maintaining the required characteristic level at a high level, and also improve chipping resistance, fracture toughness, and flexural strength.

[0067] As mentioned above, conventionally, Li metal elements are mainly used to secure properties in Mn-Zn-based electromagnetic wave absorbing compositions and electromagnetic wave absorbers, and Ca metal elements are often used to improve chipping resistance. Specifically, in the case of Li, Li elements may be included in the electromagnetic wave absorbing composition at concentrations of several hundred ppm or more, and in the case of Ca, Ca elements may be included in the electromagnetic wave absorbing composition at concentrations of 200 ppm or more. If Mn-Zn-based electromagnetic wave absorbing compositions or electromagnetic wave absorbers are manufactured without adding Li elements, a problem may arise in which primary particles become finer during manufacturing, leading to a decrease in the sintering yield.

[0068] In addition, it can be confirmed that chipping resistance is improved even when the amount of Ca element used to improve conventional chipping resistance is limited to less than 150 ppm and the amount of vanadium (V) element is also limited to less than 150 ppm.

[0069] This specification discloses preferred embodiments of the present invention. Although specific terms have been used, they are used merely in a general sense to facilitate the explanation of the technical content of the invention and to aid in understanding the invention, and are not intended to limit the scope of the invention. It is obvious to those skilled in the art that, in addition to the embodiments disclosed herein, other variations based on the technical concept of the present invention are possible. Those skilled in the art will understand that the electromagnetic wave absorbing composition and the electromagnetic wave absorber according to the embodiments described with reference to FIGS. 1 to 4 can be variously substituted, changed, and modified within the scope of the technical concept of the present invention. Therefore, the scope of the invention should not be determined by the described embodiments but by the technical concept described in the patent claims.

[0070] The electromagnetic wave absorbing composition and electromagnetic wave absorber according to the present invention can be widely used in various industrial fields where shielding and absorption of electromagnetic waves (EMI: Electromagnetic Interference) are required. In particular, since the electromagnetic wave absorbing composition of the present invention possesses excellent electromagnetic wave absorption characteristics along with thermal stability and mechanical strength, it can be usefully applied as a material for EMI / EMC countermeasures in various electronic devices, such as electronic devices, communication equipment, semiconductor packages, automotive electronic components, 5G communication modules, and radar systems, where malfunction or interference caused by electromagnetic waves is a problem.

[0071] In addition, since the electromagnetic wave absorber of the present invention can be manufactured in the form of a film, sheet, coating layer, molding material, or composite structure, it can be utilized as a component or structure for the purpose of electromagnetic shielding and absorption in a wide range of industrial fields, such as smartphones, laptops, displays, IoT devices, automotive sensors, aerospace electronics, and military communication systems.

[0072] Therefore, the present invention has very high industrial applicability as a technology capable of reducing electromagnetic interference problems caused by electromagnetic waves and improving the reliability and performance of electronic devices.

Claims

Iron oxide (Fe) having a content of 1.38 mol% to 52 mol% x O y , x=1, 2, 3, y=1, 3, 4), manganese oxide (Mn) having a content of 18 mol% to 40 mol% x O y A main component comprising zinc oxide (ZnO) having a content of 14 mol% to 30 mol% (x=1, 2, 3, y=1, 3, 4, 7); Copper oxide (Cu) having a content of 1 mol% to 4 mol% x O y x=1, 2, y=1, 2, 3) and the remainder cobalt oxide (Co x O y A subcomponent including , x=1, 2, 3, y=1, 3, 4); and An additive comprising a single element or compound containing sodium (Na) having a content of 10 ppm to 2000 ppm; Electromagnetic wave absorbing composition composed of 2. In Paragraph 1, The above additive is an electromagnetic wave absorbing composition further comprising a unit or compound containing at least one transition metal and an alkaline earth metal having a content of several hundred ppm or less.

3. In Paragraph 2, The element or compound containing the above alkaline earth metal contains calcium oxide (CaO), and The element or compound containing the above transition metal includes vanadium pentoxide (V2O5), and An electromagnetic wave absorbing composition having a total content of calcium oxide (CaO) and vanadium pentoxide (V2O5) of 300 ppm or less.

4. An electromagnetic wave absorber composed of the electromagnetic wave absorbing composition described in claim 1.

5. In Paragraph 4, The electromagnetic wave absorber has a matching thickness in the range of 4 mm to 10 mm.

6. In Paragraph 4, The above electromagnetic wave absorber has a reflection coefficient of -18dB or less at 10 MHz.

7. In Paragraph 4, The above electromagnetic wave absorber has a reflection coefficient of -22dB or less at 30 MHz. Iron oxide (Fe) having a content of 8.38 mol% to 52 mol% x O y , x=1, 2, 3, y=1, 3, 4), manganese oxide (Mn) having a content of 18 mol% to 40 mol% x O y , x=1, 2, 3, y=1, 3, 4, 7) and first raw material powders of the main component comprising zinc oxide (ZnO) having a content of 14 mol% to 30 mol%, and copper oxide (Cu) having a content of 1 mol% to 4 mol%. x O y x=1, 2, y=1, 2, 3) and the remainder cobalt oxide (Co x O y A step of preparing a second raw material powder of auxiliary components including , x=1, 2, 3, y=1, 3, 4); and an additive including a single element or compound containing sodium (Na) having a content of 10 ppm to 2000 ppm; A step of mixing the first raw material powder, the second raw material powders, and the additive; and A method for manufacturing an electromagnetic wave absorber comprising the step of forming a molded body by molding the above mixture.

9. In Paragraph 8, The step of forming a molded body by molding the above mixture A step of heat-treating the above mixture to produce intermediate particles; A step of wet-grinding the above intermediate particles; The step of mixing the above-mentioned crushed intermediate particles with a solvent to form pellets; and A method for manufacturing an electromagnetic wave absorber comprising the step of compressing the above pellets to form a molded body.

10. In Paragraph 11, A method for manufacturing an electromagnetic wave absorber comprising the step of drying the above-mentioned crushed intermediate particles.

11. In Paragraph 9, The above additive further comprises a single element or compound containing at least one transition metal and an alkaline earth metal having a content of several hundred ppm or less, and The element or compound containing the above alkaline earth metal contains calcium oxide (CaO), and The element or compound containing the above transition metal includes vanadium pentoxide (V2O5), and A method for manufacturing an electromagnetic wave absorber in which the total content of the calcium oxide (CaO) and the vanadium pentoxide (V2O5) is 300 ppm or less.

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