Rare earth element doped nickel ferrite and method for preparing the same

Abstract

The present invention relates to nickel ferrite doped with rare earth elements and a method for manufacturing the same. One embodiment of the present invention provides nickel ferrite doped with rare earth elements comprising a compound of the following chemical formula 1: [Chemical Formula 1] NiMxFe2-xO4 In the above chemical formula 1, M is a rare earth element, and x is a number greater than 0 and less than 2.

Description

Technology Field

[0001] The present invention relates to nickel ferrite doped with rare earth elements and a method for manufacturing the same. Background Technology

[0003] Spinel ferrite (MFe2O4, where 'M' is a divalent metal ion) has long been a focus of research due to its technical and scientific applications in fields such as electrochemistry, technology, magnetic fluids, synthetic biology, and high-frequency energy storage systems, as well as in electronic devices, magnetic materials, and optical devices. Furthermore, the potential for using MFe2O4 compounds as electrode materials in lithium-ion batteries and solid oxide fuel cells has recently garnered significant attention. These materials are ideal for applications in magnetic materials and electronic devices because they exhibit unique properties such as high DC electrical resistivity, large saturation magnetization, and high permeability at high frequencies. The structural formula of this ferrite is MFe2O4, where M is Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ Or it is a divalent metal ion derived from the composition of these elements. Other ions that can be included in the spinel lattice include Li + , Mg 2+ , Cr 3+ , Ti 4+ and Sb 5+ These metal ions have also been widely used as transformer cores in electronic applications due to their high resistivity and smooth FM characteristics.

[0004] Among ferrites, centrosymmetric magnetic nanophase NiFe2O4 (NFO) is a well-known material that has received significant attention due to its unique inverse spinel structure, soft FM properties, and electrical characteristics. The ductility and hardness of transition metal oxides blended with ferrite materials are useful in aerospace technology, and there is a wide range of technically excellent application possibilities in the field of magnetism, including electronic devices, magnetic fluids, organic synthesis, microwave adsorbents, smart tapes and disc recording, refrigerators, magnetic levitation systems, magnetic drug delivery, and magnetic fluids.

[0005] In particular, regarding the use of these materials in the magneto-optical field, research is continuously being conducted on how various ion substitutions affect the magnetic properties of ferrite materials.

[0007] (Patent Document 1) KR 10-2017-0124347 A The problem to be solved

[0009] The present invention provides a nickel ferrite doped with rare earth elements with improved magnetic properties and a method for manufacturing the same.

[0010] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention belongs from the description below. means of solving the problem

[0012] To achieve the above technical objective, one embodiment of the present invention provides a nickel ferrite doped with a rare earth element, comprising a compound of the following chemical formula 1:

[0013] [Chemical Formula 1]

[0014] NiM x Fe 2-x O4

[0015] In the above chemical formula 1, M is a rare earth element, and x is a number greater than 0 and less than 2.

[0016] In an embodiment of the present invention, the rare earth element may comprise at least one selected from the group consisting of europium (Eu), lanthanum (La), yttrium (Y), actinium (Ac), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and ruthenium (Lu).

[0017] In an embodiment of the present invention, the nickel ferrite doped with the rare earth element may comprise a single-phase FCC crystal structure having an Fm3m space group.

[0018] In an embodiment of the present invention, the nickel ferrite doped with rare earth elements may have a saturation magnetization (Ms) value in the range of 40 emu / g to 50 emu / g, a residual magnetization (Mr) value in the range of 20 emu / g to 35 emu / g, and a coercivity value in the range of 80 Oe to 150 Oe.

[0019] To achieve the above technical objective, another embodiment of the present invention provides a method for manufacturing nickel ferrite doped with rare earth elements, comprising the steps of: preparing a precursor mixture by mixing a nickel precursor, an iron precursor, and a rare earth precursor; preparing a combustion mixture by mixing a combustion agent into the mixture; obtaining a ash product by burning the combustion mixture; and forming nickel ferrite doped with rare earth elements by sintering the ash product.

[0020] In an embodiment of the present invention, the nickel ferrite doped with a rare earth element may comprise a compound of the following chemical formula 1:

[0021] [Chemical Formula 1]

[0022] NiM x Fe 2-xO4

[0023] In the above chemical formula 1, M is a rare earth element, and x is a number greater than 0 and less than 2.

[0024] In an embodiment of the present invention, in the step of preparing a precursor mixture by mixing the nickel precursor, the iron precursor, and the rare earth precursor, the nickel precursor and the iron precursor may be dissolved in deionized water in a molar ratio of 1:2.

[0025] In an embodiment of the present invention, the nickel precursor may comprise at least one selected from the group consisting of nickel nitrate (Ni(NO3)2), nickel sulfate (NiSO4), nickel sulfate hexahydrate (NiSO4), nickel chloride (NiCl2), nickel bromide (NiBr2), nickel fluoride (NiF2), nickel sulfamate (Ni(NH2SO3)2), and ammonium nickel sulfate ((NH4)2Ni(SO4)2) and their hydrates.

[0026] In an embodiment of the present invention, the iron precursor may comprise at least one selected from the group consisting of iron nitrate (Fe(NO3)2), iron chloride (FeCl2), iron sulfate (FeSO4), iron acetate (Fe(CH3CO2)2) and their hydrates.

[0027] In an embodiment of the present invention, the rare earth precursor may include a Europarticle precursor.

[0028] In an embodiment of the present invention, the europium precursor may comprise at least one selected from the group consisting of europium nitrate (Eu(NO3)2), europium oxide (Eu2O3), europium chloride (EuCl3), europium acetate (Eu(CH3COO)3) and hydrates thereof.

[0029] In an embodiment of the present invention, the combustion agent may comprise at least one selected from the group consisting of citric acid, malic acid, tartaric acid, acetic acid, nitric acid, succinic acid, fumaric acid, gluconic acid, glycolic acid, lactic acid, oxalic acid, salicylic acid, α-hydroxycaprylic acid, and phosphoric acid.

[0030] In an embodiment of the present invention, the step of preparing a combustion mixture by mixing a combustion agent into the mixture may involve heating the mixture to 50°C to 100°C while mixing and stirring the combustion agent with the mixture.

[0031] In an embodiment of the present invention, the step of obtaining a re-product by burning the combustion mixture may involve heating the combustion mixture to 80°C to 150°C after ignition to evaporate the water.

[0032] In an embodiment of the present invention, the step of sintering the reproduct to form nickel ferrite doped with rare earth elements may be to sinter for 30 minutes to 600 minutes at a temperature range of 500 ℃ to 1,000 ℃. Effects of the invention

[0034] According to an embodiment of the present invention, the nickel ferrite doped with rare earth elements according to the present invention exhibits increased coercivity, high dielectric constant at low frequencies, and a decrease in dielectric constant as the frequency increases. Therefore, the nickel ferrite doped with rare earth elements according to the present invention is highly useful for various applications in high-frequency microwave devices and aerospace applications.

[0035] According to an embodiment of the present invention, the method for manufacturing nickel ferrite doped with rare earth elements according to the present invention includes a combustion reaction by a sol-gel auto-combustion method from a solution state through a gel state to a powder state, so that nickel ferrite doped with rare earth elements having a single-phase FCC crystal structure having an Fm3m space group can be manufactured.

[0036] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description of the invention or the claims. Brief explanation of the drawing

[0038] FIG. 1 is a flowchart illustrating a method for manufacturing nickel ferrite doped with rare earth elements according to one embodiment of the present invention. FIG. 2 is a schematic diagram of a method for preparing Eu-doped NiFe2O4 nanoparticles according to an embodiment of the present invention. Figure 3 is a diagram showing a pit formed by the Rietveld refining method of Eu-doped NiFe2O4 nanoparticles according to an embodiment of the present invention. FIG. 4 shows pure NFO and Eu according to an embodiment of the present invention. 3+ To evaluate the thermal behavior and stability of doped NFO nanoparticles, the results of thermogravimetric analysis at 5 °C / min in nitrogen are shown. FIG. 5 shows pure NFO nanoparticles and Eu according to an embodiment of the present invention. 3+ This is an FESEM microscope image of a sample of doped NFO nanoparticles. FIG. 6 is an external m according to an embodiment of the present invention. 0. Pure and Eu in ZFC and FC modes at H = 0.5 T 3+ - This is the isothermal magnetic measurement [M(T)] obtained for doped NFO nanoparticles. Fig. 7 shows Eu subjected to a magnetic field of 2T at room temperature. 3+This is the result showing the isothermal magnetization [M(H)] of the doped NFO sample. FIG. 9 is a figure showing Mr, Ms, Hc, and Rs of Eu-doped NFO nanoparticles at room temperature according to an embodiment of the present invention. FIG. 10 is a diagram showing ε', ε'', and Tan δ of Eu-doped NFO nanoparticles at room temperature according to an embodiment of the present invention. Specific details for implementing the invention

[0039] The present invention will be described below with reference to the attached drawings. However, the present invention may be implemented in various different forms and is therefore not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification have been given similar reference numerals.

[0040] Throughout the specification, when it is stated that a part is "connected (connected, in contact, combined)" with another part, this includes not only cases where they are "directly connected," but also cases where they are "indirectly connected" with other members interposed between them. Furthermore, when it is stated that a part "includes" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but rather allows for the inclusion of additional components.

[0041] The terms used herein are merely for describing specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising” or “having” are intended to indicate the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0043] Embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0045] One embodiment of the present invention provides a nickel ferrite doped with a rare earth element, comprising a compound of the following chemical formula 1:

[0046] [Chemical Formula 1]

[0047] NiM x Fe 2-x O4

[0048] In the above chemical formula 1, M is a rare earth element, and x is a number greater than 0 and less than 2.

[0049] The above rare earth element may include at least one selected from the group consisting of europium (Eu), lanthanum (La), yttrium (Y), actinium (Ac), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and ruthenium (Lu).

[0050] Preferably, the rare earth element may be europium (Eu).

[0051] Accordingly, the nickel ferrite doped with a rare earth element according to one embodiment of the present invention may be NiEuFeO4, which is a compound represented by the following chemical formula 2:

[0052] [Chemical Formula 2]

[0053] NiEuFe 2-x O4

[0054] In the above chemical formula 2, x is a number greater than 0 and less than 2.

[0055] Preferably, the above x may be 0.02 to 0.15.

[0056] The nickel ferrite doped with the above rare earth element may include a single-phase FCC crystal structure having an Fm3m space group.

[0057] When the crystals on the particle surface of the nickel ferrite doped with the rare earth element of the present invention were analyzed using powder X-ray diffraction (PXRD), it was found that it contains a single-phase FCC crystal structure having the Fd3M space group.

[0058] The nickel ferrite doped with the rare earth element above may have an average crystal grain size of nanoparticles of 220 nm to 250 nm; 220 nm to 240 nm; 220 nm to 230 nm; 225 nm to 250 nm; 225 nm to 240 nm; 225 nm to 230 nm; 230 nm to 250 nm; 230 nm to 240 nm; or 240 nm to 250 nm.

[0059] Preferably, the average grain size of the nickel ferrite nanoparticles doped with the rare earth element may be 225 nm to 250 nm.

[0060] The nickel ferrite doped with the above rare earth element has a saturation magnetization (Ms) value of 40 emu / g to 50 emu / g; 40 emu / g to 48 emu / g; 40 emu / g to 46 emu / g; 40 emu / g to 44 emu / g; 40 emu / g to 42 emu / g; 42 emu / g to 50 emu / g; 42 emu / g to 48 emu / g; 42 emu / g to 46 emu / g; 42 emu / g to 44 emu / g; 44 emu / g to 50 emu / g; 44 emu / g to 48 emu / g; 44 emu / g to 46 emu / g; 46 emu / g to 50 emu / g; 46 emu / g to 48 emu / g; Or it may be in the range of 48 emu / g to 50 emu / g.

[0061] The nickel ferrite doped with the rare earth element above has a residual magnetization (Mr) value in the range of 20 emu / g to 35 emu / g; 20 emu / g to 33 emu / g; 20 emu / g to 30 emu / g; 20 emu / g to 28 emu / g; 20 emu / g to 25 emu / g; 20 emu / g to 23 emu / g; 23 emu / g to 35 emu / g; 23 emu / g to 33 emu / g; 23 emu / g to 30 emu / g; 23 emu / g to 28 emu / g; 23 emu / g to 25 emu / g; 25 emu / g to 35 emu / g; 25 emu / g to 33 emu / g; It may be in the range of 25 emu / g to 30 emu / g; the range of 25 emu / g to 28 emu / g; the range of 28 emu / g to 35 emu / g; the range of 28 emu / g to 33 emu / g; the range of 28 emu / g to 30 emu / g; the range of 30 emu / g to 35 emu / g; the range of 30 emu / g to 33 emu / g; or the range of 33 emu / g to 35 emu / g.

[0062] The nickel ferrite doped with the rare earth element above may have a coercivity value in the range of 80 Oe to 150 Oe; 80 Oe to 130 Oe; 80 Oe to 100 Oe; 90 Oe to 150 Oe; 90 Oe to 130 Oe; 90 Oe to 100 Oe; 100 Oe to 150 Oe; 100 Oe to 130 Oe; 110 Oe to 150 Oe; 110 Oe to 130 Oe; 120 Oe to 150 Oe; 120 Oe to 130 Oe; or 130 Oe to 150 Oe.

[0063] Doping rare earth elements into the Fe sites reduced the saturation magnetization value, while the total coercivity increased with the concentration of rare earth elements; this may be due to the enhancement of crystal magnetic anisotropy caused by anisotropic Fe ions located in the tetrahedral sites. Substituting rare earth elements may reduce the hopping rate of Fe at the octahedral sites of the doped nanoparticles, which could lead to a decrease in both the dielectric constant and the loss factor.

[0064] Nickel ferrite doped with rare earth elements according to one embodiment of the present invention exhibits increased coercivity, high dielectric constant at low frequencies, and a decrease in dielectric constant as the frequency increases. Therefore, nickel ferrite doped with rare earth elements according to the present invention is highly useful for various applications in high-frequency microwave devices and aerospace applications. In particular, it is highly useful for application in hypersonic flow environments.

[0066] Another embodiment of the present invention provides a method for manufacturing nickel ferrite doped with rare earth elements, comprising the steps of: preparing a precursor mixture by mixing a nickel precursor, an iron precursor, and a rare earth precursor; preparing a combustion mixture by mixing a combustion agent into the mixture; obtaining a reproduct by burning the combustion mixture; and forming nickel ferrite doped with rare earth elements by sintering the reproduct.

[0067] FIG. 1 is a flowchart illustrating a method for manufacturing nickel ferrite doped with rare earth elements according to one embodiment of the present invention.

[0068] Referring to FIG. 1, a method for manufacturing nickel ferrite doped with rare earth elements according to one embodiment of the present invention comprises a precursor mixture preparation step (110), a combustion mixture preparation step (120), a reproduct obtaining step (130), and a reproduct sintering step (140).

[0069] The above precursor mixture preparation step (110) is to prepare a precursor mixture by mixing a nickel precursor, an iron precursor, and a rare earth precursor.

[0070] The nickel precursor may comprise at least one selected from the group consisting of nickel nitrate (Ni(NO3)2), nickel sulfate (NiSO4), nickel sulfate hexahydrate (NiSO4), nickel chloride (NiCl2), nickel bromide (NiBr2), nickel fluoride (NiF2), nickel sulfamate (Ni(NH2SO3)2), and ammonium nickel sulfate ((NH4)2Ni(SO4)2) and their hydrates.

[0071] Preferably, the nickel precursor may be Ni(NO3)2.6H2O (nickel nitrate hydrate).

[0072] The above iron precursor may comprise at least one selected from the group consisting of iron nitrate (Fe(NO3)2), iron chloride (FeCl2), iron sulfate (FeSO4), iron acetate (Fe(CH3CO2)2) and their hydrates.

[0073] Preferably, the iron precursor may be Fe(NO3)3.9H2O (ferrous nitrate hydrate).

[0074] The above rare earth precursor may include a Europarticle precursor.

[0075] The europium precursor may comprise at least one selected from the group consisting of europium nitrate (Eu(NO3)2), europium oxide (Eu2O3), europium chloride (EuCl3), europium acetate (Eu(CH3COO)3) and hydrates thereof.

[0076] Preferably, the europium precursor is Eu(NO3) 2.5 It may be using H2O (europium nitrate hydrate).

[0077] In the step of preparing a precursor mixture by mixing the nickel precursor, iron precursor, and rare earth precursor, the nickel precursor and iron precursor may be dissolved in deionized water in a molar ratio of 1:2.

[0078] The above combustion mixture preparation step (120) is to prepare a combustion mixture by mixing a combustion agent into the mixture.

[0079] The above combustion agent may include at least one selected from the group consisting of citric acid, malic acid, tartaric acid, acetic acid, nitric acid, succinic acid, fumaric acid, gluconic acid, glycolic acid, lactic acid, oxalic acid, salicylic acid, α-hydroxycaprylic acid, and phosphoric acid.

[0080] Preferably, the combustion agent may be citric acid.

[0081] The step of preparing a combustion mixture by mixing a combustion agent into the above mixture may involve mixing the combustion agent into the above mixture and stirring while heating to 50 ℃ to 100 ℃; 50 ℃ to 90 ℃; 50 ℃ to 80 ℃; 50 ℃ to 70 ℃; 50 ℃ to 60 ℃; 60 ℃ to 100 ℃; 60 ℃ to 90 ℃; 60 ℃ to 80 ℃; 60 ℃ to 70 ℃; 70 ℃ to 100 ℃; 70 ℃ to 90 ℃; 70 ℃ to 80 ℃; 80 ℃ to 100 ℃; 80 ℃ to 90 ℃; or 90 ℃ to 100 ℃.

[0082] Preferably, the step of preparing the combustion mixture may be to heat it in a temperature range of 70°C to 90°C.

[0083] The step of obtaining the above-mentioned reproduct (130) is to obtain the reproduct by burning the combustion mixture.

[0084] The step of obtaining a re-product by burning the combustion mixture comprises, after ignition of the combustion mixture, 80 ℃ to 150 ℃; 80 ℃ to 140 ℃; 80 ℃ to 130 ℃; 80 ℃ to 120 ℃; 80 ℃ to 110 ℃; 80 ℃ to 100 ℃; 80 ℃ to 90 ℃; 90 ℃ to 150 ℃; 90 ℃ to 140 ℃; 90 ℃ to 130 ℃; 90 ℃ to 120 ℃; 90 ℃ to 110 ℃; 90 ℃ to 100 ℃; 100 ℃ to 150 ℃; 100 ℃ to 140 ℃; 100 ℃ to 130 ℃; 100 ℃ to 120 ℃; Water may be evaporated by heating to 100 ℃ to 110 ℃; 120 ℃ to 150 ℃; 120 ℃ to 140 ℃; 120 ℃ to 130 ℃; 130 ℃ to 150 ℃; or 130 ℃ to 140 ℃.

[0085] Preferably, the combustion mixture may be heated to 90°C to 110°C after ignition to evaporate excess water.

[0086] The above-mentioned reproduct sintering step (140) is to sinter the reproduct to form nickel ferrite doped with rare earth elements.

[0087] In an embodiment of the present invention, the step of sintering the reproduct to form nickel ferrite doped with rare earth elements comprises: 500 ℃ to 1,000 ℃; 500 ℃ to 900 ℃; 500 ℃ to 800 ℃; 500 ℃ to 700 ℃; 500 ℃ to 600 ℃; 600 ℃ to 1,000 ℃; 600 ℃ to 900 ℃; 600 ℃ to 800 ℃; 600 ℃ to 700 ℃; 700 ℃ to 1,000 ℃; 700 ℃ to 900 ℃; 700 ℃ to 800 ℃; 800 ℃ to 1,000 ℃; 800 ℃ to 900 ℃; Or, sintering may be performed at a temperature range of 900 ℃ to 1,000 ℃ for 30 minutes to 600 minutes; 30 minutes to 500 minutes; 30 minutes to 300 minutes; 30 minutes to 100 minutes; 60 minutes to 600 minutes; 60 minutes to 500 minutes; 60 minutes to 300 minutes; 60 minutes to 100 minutes; 120 minutes to 600 minutes; 120 minutes to 500 minutes; 120 minutes to 300 minutes; 240 minutes to 600 minutes; 240 minutes to 500 minutes; 240 minutes to 300 minutes; 360 minutes to 600 minutes; 360 minutes to 500 minutes; 480 minutes to 600 minutes.

[0088] Preferably, the sintering of the above-mentioned product may be performed at a temperature range of 600°C to 900°C for 60 minutes to 300 minutes.

[0089] The nickel ferrite doped with the rare earth element manufactured by sintering may be in the form of nanoparticles in powder form.

[0090] The nickel ferrite doped with the above rare earth element may comprise a compound of the following chemical formula 1:

[0091] [Chemical Formula 1]

[0092] NiM x Fe 2-x O4

[0093] In the above chemical formula 1, M is a rare earth element, and x is a number greater than 0 and less than 2.

[0094] The above rare earth element may include at least one selected from the group consisting of europium (Eu), lanthanum (La), yttrium (Y), actinium (Ac), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and ruthenium (Lu).

[0095] Preferably, the rare earth element may be europium (Eu).

[0096] Accordingly, the nickel ferrite doped with a rare earth element according to one embodiment of the present invention may be NiEuFeO4, which is a compound represented by the following chemical formula 2:

[0097] [Chemical Formula 2]

[0098] NiEuFe 2-x O4

[0099] In the above chemical formula 2, x is a number greater than 0 and less than 2.

[0100] Preferably, the above x may be 0.02 to 0.15.

[0101] The method for producing nickel ferrite doped with rare earth elements according to the present invention includes a combustion reaction by a sol-gel auto-combustion method from a solution state through a gel state to a powder state, so that nickel ferrite doped with rare earth elements having a single-phase FCC crystal structure having an Fm3m space group can be produced.

[0102] Furthermore, since a sol-gel is formed, highly uniform mixing is possible; because the starting materials are dissolved in an aqueous solution, it is easy to adjust the chemical composition; and because organometallic salts with large molecular weights coordinated to organic materials are not used, the yield of nickel ferrite doped with rare earth elements is high.

[0104] The present invention will be explained in more detail below through examples.

[0105] However, the following examples are merely for illustrating the present invention, and the content of the present invention is not limited to the following examples.

[0107] [Example]

[0108] In an embodiment of the present invention, rare earth Eu 3+ NiFe2O4 (x = 0.00, 0.04, 0.08, 0.12) nanoferrites doped with Eu... were prepared using a sol-gel auto-combustion method. Eu... regarding the structural, morphological, thermal, magnetic, and dielectric properties of NiFe2O4... 3+ The effect of doped NiFe2O4 is observed. The XRD patterns of the samples show that samples x = 0.00, 0.04, and 0.08 have a single-phase FCC structure with an Fd3m space group, whereas sample x = 0.12 has a higher Eu 3+ It was confirmed that secondary phase EuFeO3 formation occurs at this concentration.

[0109] Based on XRD analysis, as Eu content increases, the lattice constant (a c) and cell volume increase. Furthermore, TGA analysis shows thermal decomposition and weight loss of the pure and doped materials. According to FESEM analysis, Eu 3+ The addition of [it] generates nanoparticles (NPs) with an average particle size of 220–250 nm, and the EDAX spectrum indicates the presence of Eu, Ni, Fe, and O, as confirmed by elemental mapping. Furthermore, the room temperature magnetic hysteresis curves show clearly defined soft FM behavior for all prepared nanoparticles, with saturation magnetization (Ms) values ​​ranging from 48.42 emu / g to 43.15 emu / g and remanent magnetization (Mr) ranging from 32.64 emu / g to 23.65 emu / g. However, Fe 3+ Eu on the site 3+ Replacing ions increases the overall coercivity (90 Oe - 140 Oe). Additionally, the permittivity (ε') of all samples is high at low frequencies and gradually decreases as the frequency increases. Furthermore, Fe at the octahedral positions of the doped nanoparticles 3+ Because the hopping rate for decreases, Eu 3+ Substituting it reduces both the dielectric constant (ε') and the loss factor (tan δ). Therefore, a lower tan δ value is Eu 3+ - This indicates that doped NiFe2O4 nanoparticles are suitable for high-frequency microwave device applications.

[0111] Experimental Procedure

[0112] Synthesis process

[0113] 99.99% purity analytical grade Ni(NO3)2.6H2O (nickel nitrate), Fe(NO3)3.9H2O (iron nitrate) and Eu(NO3) 2.5 H2O (Europium Nitrate) was purchased from Sigma Aldrich.

[0114] FIG. 2 is a schematic diagram of a method for preparing Eu-doped NiFe2O4 nanoparticles according to an embodiment of the present invention.

[0115] As shown in Fig. 2, using the sol-gel auto-combustion method, NiEu x Fe 2-x O4 (where x = 0.00, 0.04, 0.08, 0.12 (referred to as Eu-0, Eu-4, Eu-8, and Eu-12 NPs, respectively)) nanoparticles (NPs) were prepared. Additionally, Ni(NO3)26H2O and Fe(NO3)39H2O were dissolved in deionized water at a 1:2 M ratio and stirred separately for 20 minutes. Finally, an aqueous solution of C6H8O7 (citric acid acting as a combustion agent) was slowly mixed into the solution and heated to 80 °C while stirring. After ignition, the re-product was heated to 100 °C to evaporate excess water. To form normal-phase crystals, the final product was annealed at 800 °C for 2 hours at a rate of 7 °C / min.

[0117] Specialized technology

[0118] Powder X-ray diffraction (PXRD) was performed using a Rigaku Smart-Lab XRD instrument with Cu K radiation operating at 40 kV and 30 mA, and a field emission scanning electron microscope (FESEM, Zeiss Ultra 55) was used for morphological analysis. In addition, thermogravimetric analysis (SII TG / DTA 6200 EXSTAR) was performed in a nitrogen atmosphere at temperatures ranging from 25 to 1000 °C with a heating rate of 5 °C / min to study the stability and weight loss trends of the samples at these temperatures. Isothermal magnetization was measured in an applied magnetic field of 2.5 T using a magnetometer (Quantum Design, MPMS 3), and thermomagnetic properties were investigated in the zero-field cooling and field cooling temperature ranges between 300 K and 2 K in helium. To perform genomic analysis, a programmable precision LCR bridge (Keysight: E4980A) was utilized in a frequency range of 100 Hz to 2 MHz at RT, and highly conductive silver layers were placed on both sides of the pellet (13 mm × 1.2 mm) to improve the ohmic contact of the material.

[0120] Results and Discussion

[0121] Figure 3 is a diagram showing a pit formed by the Rietveld refining method of Eu-doped NiFe2O4 nanoparticles according to an embodiment of the present invention.

[0122] Specifically, Figure 3 shows the Rietveld refinement fitting performed using the FULLPROF program to obtain the structural parameters of Eu-doped NiFe2O4 nanoparticles. The observed values ​​were 18.75°, 30.66°, 35.90°, 37.53°, 43.79°, 54.09°, 57.72°, and 63.43°, respectively, thus confirming a single-phase FCC structure with a space group of Fd3m. This is in good agreement with the values ​​of reference JCPDS card number: 86-226. Clearly, Eu in pure spinel ferrite 3+ As substitution (Eu = 12) increased, a secondary phase of EuFeO3 was observed at the maximum substitution of Eu. This concerns the secondary phase of EuFeO3. Clearly, Eu 3+ The ionic radius of is NiFe 2-x Eu x It had a significant effect on the formation of the EuFeO3 phase in the O4 sample. Fe 3+ Compared to the ion (0.67), Eu 3+ The ion (1.07) was larger. Also, Fe 3+ The amount of ions is Eu in the octahedral regions of the spinel system. 3+ It can be replaced by. This is excessive Eu 3+ This means that the Eu2O3 phase is formed as an impurity at the grain boundaries. The high-intensity peak of the reflection surface (311) shifted toward a lower diffraction angle as the Eu content increased due to internal stress generated by the distribution of dopant cations. Pure NFO and Eu 3+ The structural parameters of the doped NFO samples were calculated using the following mathematical formulas 1 to 6.

[0123] [Mathematical Formula 1]

[0124] D = kλ / (βcosθ)

[0125] [Mathematical Formula 2]

[0126]

[0127] [Mathematical Formula 3]

[0128] v=a 3

[0129] [Mathematical Formula 4]

[0130]

[0131] [Mathematical Formula 5]

[0132]

[0133] [Mathematical Formula 6]

[0134]

[0135] Here, D represents the average crystal size (nanometer). k represents the shape factor, with a value of 0.94. β represents the FWHM; λ represents the wavelength of the X-rays used. is the Bragg diffraction angle. a c is the lattice constant; d is the interplanar spacing. h, k, and l are Miller indices. v is the volume of the unit cell. M is the molecular mass; N is Avogadro's number. The typical crystal size of the samples was observed in the range of 29–33 nm. Tensile strain increased with increasing Eu content. Fe 3+ Eu in samples larger in size compared to ions 3+ It is thought that in the presence of ions, tensile strain increases depending on the Eu concentration. Eu 3+ The ion is smaller Fe 3+ Replacing the ion a c Å increased from 8.26 to 8.30 Å, and the cell volume became 564.4 Å. 3 at 573.3 Å 3 Increased to. Eu 3+ X-ray density is 5.42 g / cm³ due to ion substitution 3 At 5.46 g / cm³ 3 It increased. As the Eu concentration increases, the hopping length between A-sites and B-sites increases. This is because conductivity decreases as charge carriers require more energy to move between cation sites. Here, the fit of the fitting parameters (χ² 2), weighted profile confidence (R wp ) and profile confidence index (R p The accuracy of the improvement was analyzed using ) (Table 1).

[0136] Table 1 below is Eu 3+ These are the structural parameters of doped NiFe2O4.

[0137] Eu 3+ D(nm) a(Å) V(Å 3 ) r x (g / cm 3 ) L A L B χ2 R wp R p Eu-0 33.4 8.26 564.43 5.42 3.57 2.92 3.9 20.4 31.5 Eu-4 30.2 8.28 568.68 5.42 3.58 2.92 3.1 16.3 30.8 Eu-8 29.1 8.30 573.30 5.50 3.59 2.93 3.3 34.9 30.7 Eu-12 29.0 8.30 573.30 5.46 3.59 2.93 3.5 34.8 33.0

[0138] The observed and calculated diffraction patterns were found to have a strong relationship, which is due to the goodness of fit (χ² 2 It indicates that ) is less than 10%.

[0139] FIG. 4 shows pure NFO and Eu according to an embodiment of the present invention. 3+ To evaluate the thermal behavior and stability of doped NFO nanoparticles, the results of thermogravimetric analysis at 5 °C / min in nitrogen are shown.

[0140] The sample shown in Fig. 4(a) demonstrates that pyrolysis occurred in two distinct stages. An initial 0.1% weight loss stage occurred between 25 and 400 °C and was associated with hydroxyl removal. Residual fuel caused a second weight loss stage of 0.3% between 400 and 800 °C. Crystalline NiFe2O4 was formed in the final weight loss range of 800 °C to 1000 °C. A 0.1% weight loss stage in the temperature range of 25 °C to 150 °C is shown in Fig. 4(b). Residual fuel caused a second weight loss stage of 0.1%, which occurred between 250 °C and 800 °C. Crystalline NiFe2O4 was formed in the final weight loss range of 800 °C to 1000 °C. The sample in Fig. 4(c) exhibits a weight loss step of 0.1% up to 600 ℃, which corresponds to the removal of hydroxyl groups. After removing the remaining fuel, a weight loss step of 0.3% occurred, which was observed in the temperature range of 600–800 ℃. The formation of crystalline NiFe2O4 appears as a final loss in the temperature range of 800 ℃–1,000 ℃.

[0142] FIG. 5 shows pure NFO nanoparticles and Eu according to an embodiment of the present invention. 3+ This is an FESEM microscope image of a sample of doped NFO nanoparticles.

[0143] The microscopic images in Fig. 5 provide a comprehensive microstructural examination of the particle size, shape, and aggregation of the synthesized material, showing the pure NFO NPs in Figs. 4 (a)–(d) as highly aggregated, densely packed heterogeneous particles. Larger particle size and greater aggregation enhanced the magnetic moment, which was associated with volume and aggregation. Furthermore, due to large aggregation, the NFO material was permanently magnetized, and the average grain size of the NPs ranged from 220 to 250 nm, RE Eu 3+Homogeneous grains were observed in the oxide. Therefore, microstructural analysis is essential for understanding magnetic reinforcement and directly influenced the electrical properties of the prepared NPs. The large grain size can alter the grains (Gs) and grain boundaries (GB), consequently hindering the electrical flow of the MFe2O4 material. Furthermore, micrographs of each prepared sample show the development of cubic grains, indicating that the grains essentially maintained a cubic shape during grain growth. Moreover, EDAX measurements showed Fe 3+ Eu in the area 3+ Since the addition of [it] slightly increases the average particle size, as shown in Table 2 below, it suggests that the synthesized Eu-doped NFO is stoichiometric and has a uniform distribution of elements.

[0144] X(I 3+ ) Ni at. % Fe at. % Eu at. % O at. % Particle Size (nm) Eu-0 19.85 37.36 - 42.79 220 Eu-4 17.49 36.73 1.98 43.78 229 Eu-8 18.69 38.76 2.43 40.12 240 Eu-12 23.43 38.12 4.81 33.64 249

[0145] FIG. 6 is an external m according to an embodiment of the present invention. 0. Pure and Eu in ZFC and FC modes at H = 0.5 T 3+ - This is the isothermal magnetic measurement [M(T)] obtained for doped NFO nanoparticles.

[0146] Referring to Figure 6, the difference between the ZFC curve estimates is shown. 6.13 emu.g at 5 K -1 As the magnetization and temperature decrease, the magnetization value of the FC curve increases, reaching 7.38 emu.g at 5K. -1 It reaches. If the connection between the ZFC and FC curves breaks as the temperature decreases, it indicates the presence of non-equilibrium magnetization. T where the FC and ZFC curves diverge. irr For pure and doped materials, indicated by (irreversible temperature), it is a state below 300 K. Additionally, the FC curve shows that as the temperature is increased and the magnetization is decreased between 5 K and 300 K, the individual μ for the entire configuration BIt shows that strong dipole-magnetic interactions occur between them. In contrast, the ZFC curve is closely related to the energy barrier distribution and high thermal Tirr. Also, Eu 3+ -Doped NFO NP is Fe 3+ Eu on the site 3+ It exhibited the same trend as the pure material in that the magnetization value decreased with the addition of. Eu according to the difference in magnetization values ​​between the FC (at 5 K) and ZFC (at 300 K) curves 3+ The tetravalent non-magnetic REE ion of Fe at the B site 3+ Attempting to partially replace the ions, Eu as listed in Table 3 3+ The substitution of Fe 3+ μ lower than the substitution of (51B) B The magnetization is reduced because it has (3.51B).

[0147] Table 3 below shows M at 5 K and 300 K from the ZFC and FC curves of Eu-0, Eu-4, Eu-8, and Eu-12 according to an embodiment of the present invention. s It represents the value.

[0148] Temp K Eu-0 Eu-4 Eu-8 Eu-12 FC emu.g -1 FC emu.g -1 FC emu.g -1 ZFC emu.g -1 FC emu.g -1 ZFC emu.g -1 FC emu.g -1 ZFC emu.g -1 5 K 7.39 6.13 6.96 5.29 5.71 3.39 4.94 3.10 300 K 6.91 6.91 6.73 6.70 5.28 5.28 4.62 4.62

[0149] Here, magnetization is REE(Eu 3+ ) μ of the ion B It decreases due to. Generally, it is accompanied by local 4f electrons. This is because spins require more thermal energy to be emitted from the NP axis, so as temperature increases, μ B This is because alignment of μ0.H is possible. Most of the saturation magnetization in MFe2O4 originates from interactions between cations at the A and B sites. Neel's FI model states that AA and BB interactions within the sublattice are less important than the net magnetic moment arising from AB exchange interactions and the difference between B in the A and B sublattices. The B sublattice is oriented in the opposite direction. In MFe2O4 material, Fe 3+While ions contribute to the magnetization of the A and B sublattices, Ni 2+ and Eu 3+ The ion contributes only to the magnetization of the B sublattice. In light of the previously mentioned, the pure μ B is Fe 3+ Eu for the B site of the NFO spinel lattice to minimize ions 3+ It is expected to decrease due to the preferential occupancy of ions. The results show that net magnetization decreases as the concentration of REE Eu3+ increases, which is Fe(A) 3+ -O 2- -Eu(B) 3+ Superexchange interaction is Fe(A) 3+ -O 2- -Fe(B) 3+ It means relatively weaker than the interaction.

[0151] Fig. 7 shows Eu subjected to a magnetic field of 2T at room temperature. 3+ This is the result showing the isothermal magnetization [M(H)] of the doped NFO sample.

[0152] Referring to Fig. 7, the magnitude of the magnetization saturated at approximately 0.5 T for all compositions and remained constant up to a maximum field of 2 T. The MS value is Fe 3+ Eu on the site 3+ It was reduced by doping, and the MS values ​​of the pure and doped compositions decreased. For Eu = 0, 4, 8, and 12, the values ​​were 48.42, 47.72, 45.27, and 43.15 emu.g., respectively. -1 is. The enlarged version of Fig. 6(b) shows the reduction of Ms and Eu 3+ This shows that the increase is due to changes occurring at the spinel ferrite lattice positions as the REE oxide content increases. Similarly, REE Nd 3+ and Eu 3+ Doping with oxide elements tended to decrease the MS value. Generally, the ability of metal cations occupying the B and A sites depends on the ionic radius of the selected element, and in the spinel lattice, trivalent Fe3+ The ion has a higher ionic radius Eu 3+ It is replaced by ions, affecting magnetic exchange interactions and leading to changes in the magnetic properties of the desired composition. The magnetization of MFe2O4NP is generally at a crystal size μ B and is determined by changes in the cation occupancy positions. Furthermore, the magnetic behavior of MFe2O4NP is determined by superexchange interactions with disordered metal cations as well as Eu 3+ It is influenced by the composition of doped NFO. In addition, trivalent Fe, an important component of MFe2O4, 3+ Ions generally form magnetic moments. Consequently, dopants form Fe through 4f-3d coupling 3+ Ions (Eu 3+ -O-Fe 3+ Replacing ) Fe 3+ -O-Fe 3+ Magnetic exchange interactions between ions and Eu in the NFO spinel lattice 3+ It can affect ion integration. Therefore, the ionic radius of the element plays an important role, and the AB interaction between the REE oxide and the MFe2O4 lattice increases or decreases the magnetic properties of the prepared NPs. The decreasing magnetization trend of MFe2O4 NPs is related to the Fe at the B site. 3+ (0.64 Å) ions with a larger ionic radius Eu 3+ This is attributed to the replacement with (1.01 Å) ions, which is desirable for the A site to be occupied by ions with a smaller ionic radius. The M(T) curve exhibits smooth FM characteristics at both low and high temperatures, as confirmed by the M(H) curves for the pure and Eu-doped samples shown in the magnified views of Figures 7 (b) and (c).

[0153] FIG. 8 shows pure water and Eu at different temperatures among m0.H = 2.5 T according to an embodiment of the present invention. 3+ - This is the M(H) result of doped NFO nanoparticles.

[0154] Referring to Fig. 8, Eu 3+The M(H) measurement of doped NFO is μ 0. Tests were performed at lower and higher temperatures of 10 K, 100 K, 200 K, and 300 K at H = 2.5 T. As indicated by the M(T) FC curve, the MS values ​​increased for all compositions as the temperature decreased. The MS values ​​for the pure and doped compositions were 53.71, 51.82, and 49.15 emu.g for Eu = 0, 8, and 12, respectively. -1 It was [at 10 K]. The presence of soft FM hysteresis loops at both lower and higher temperatures indicates that Eu doping at Fe sites confirmed soft FM characteristics.

[0155] Table 4 shows the Ms and H of Eu-0, Eu-4, Eu-8, and Eu-12 according to an embodiment of the present invention. C This shows the magnetic properties and right-angle ratio (Rs) values ​​of Mr (magnetic residual magnetism).

[0156] Eu 3+ Ms Mr H c Rs Eu-0 48.42 32.64 96 0.674 Eu-4 47.72 29.97 118 0.628 Eu-8 45.27 26.79 126 0.591 Eu-12 43.15 23.65 140 0.548

[0157] The Mr values ​​of Eu-doped NPs range from 32.64 to 23.65 emu.g -1 It was in the range, and the Mr value decreased. Substituted elements in NFO (Eu 3+ As the number of ) increases. Dy 3+ Doped NFO and Gd 3+ The same phenomenon was observed in doped CFO as well. Furthermore, the same pattern of Mr values ​​was observed in the MS of the fabricated NPs, indicating that Mr depends on the grain alignment induced by superexchange interactions between the MS of the synthesized NPs and the MFe2O4NPs. In addition, the H of the material C HC was an important factor in the magnetic properties of MFe2O4NP, and the HC values ​​of the Eu-doped samples were 96 Oe, 118 Oe, 126 Oe, and 140 Oe for Eu = 0, 4, 8, and 12, respectively. HC is Eu 3+It increased with the concentration, which is due to the anisotropic Fe located in the tetrahedral region. 2+ It could be a result of crystallographic magnetic anisotropy being enhanced by ions. Also, H C It is considered a microstructural characteristic and is influenced by various factors such as surface effects, deformation, non-magnetic atoms, magnetic exchange interactions between collinear spins and oblique spins on the core, and material defects. Additionally, the parameter Rs was derived from the ratio of Mr / MS, and this value decreased as the amount of Eu in Fe sites increased. Generally, high Rs values ​​are preferred for applications in memory devices and recording media. Furthermore, the presence of magnetostatic interactions in multi-domain NPs at room temperature is demonstrated by Rs being greater than 0.5 for all configurations, and higher Rs indicates random orientations similar to those of non-interacting NPs with cubic magnetocrystalline anisotropy. Fig. 9 is a figure showing Mr, Ms, Hc, and Rs of Eu-doped NFO nanoparticles at room temperature according to an embodiment of the present invention.

[0159] FIG. 10 is a diagram showing ε', ε'', and Tan δ of Eu-doped NFO nanoparticles at room temperature according to an embodiment of the present invention.

[0160] Referring to Fig. 10, the room temperature permittivity (ε'), the imaginary part (ε') of the dielectric, and the loss factor (Tan δ) for frequencies ranging from 100 Hz to 2 MHz indicate that general behavior occurs and the value of ε' decreases over time. Using samples with increasing frequencies between 1 kHz and 2 MHz, the dielectric exhibits general dispersion behavior as shown in Fig. 10(a). Generally, dispersion behavior is elucidated by the Maxwell-Wagner model, which describes dispersion with respect to frequency based on Koop's theory. According to Koop's theory, the material can be composed of two layers. The first layer consists of a highly conductive G layer separated by short intervals by short, low-conductivity layers. The GB effect is dominant at low frequencies, whereas G is effective at high frequencies. According to Koop's theory, dielectric structures possess a well-dielectric G where the GB is not well separated, and Maxwell-Wagner interfacial polarization, which aligns well with Koop's theory, leads to the observation of dispersion in ε' at higher or lower frequencies relative to the magnetic flux. According to this theory, dispersion is influenced by the non-uniform nature of dielectric structures composed of two layers. The combined response of ions, space charge, and interfacial polarization is responsible for the observation of maximum dielectric constant values ​​in the lower frequency region, and interfacial polarization occurs when different conductive phases coexist within the same material. The observation of independent ε' in the higher frequency region implies that the dipole cannot be sustained by fluctuations caused by changes in the applied electric field. Therefore, according to the analysis, G is effective in the high-frequency region, while GB is more effective for ε' in the low-frequency region. Fe 2+ and Fe 3+The exchange of electrons between ions is independent of the frequency of the AC electric field applied to MFe2O4. Here, the polarization of NFO is related to charge carrier hopping. This may be because polarization decreases as the frequency of the applied AC electric field increases. Therefore, Fe 3+ Eu at location 3+ When added, the ε' of the substance decreases, while the amount of non-magnetic ions increases, and Eu 3+ It was analyzed that ion doping does not have a greater effect in the high-frequency region. Therefore, Eu 3+ to Fe 3+ When added to the site, Eu 3+ An increase in concentration [fe] some Fe3+ ions 2+ It was transformed to generate charge neutrality, which is Fe 3+ and Fe 2+ This can be caused by reduced hopping between ions and a decrease in grain resistance, which can lead to a decrease in the material's e'. ε” is shown for different temperatures and frequencies in Fig. 10(b). A similar pattern was obtained for ε'' in the case of ε'. The ratio of the dielectric constant ε” to ε' can be used here to express tan δ, which is commonly used to describe energy loss and δ (angle). According to Fig. 10(c), the loss tangent exhibits very low values ​​across the entire temperature and frequency range, indicating the intrinsic properties of the material. Generally, tan δ is attributed to the dipole polarization delay occurring after the application of an alternating field and may result from crystal lattice defects, GB, and impurities in MFe2O4. Additionally, Eu 3+ The frequency-dependent dispersion of tan δ, which begins to decrease with the substitution of , can be explained by the Maxwell-Wagner model. Therefore, material density plays a crucial role in controlling loss variations. In the low-frequency region, the presence of Gs generally corresponds to high resistivity (reason for GB), and vice versa, and Fe in the low-frequency region 2+and Fe 3+ The material is generated due to the high energy required for electron exchange between ions. Similarly, as the frequency increases, the energy required for electron transfer between two Fe ions at the B site decreases, and as the frequency increases, the ε'' value decreases, indicating that it is suitable for use in high-frequency devices.

[0162] conclusion

[0163] In an embodiment of the present invention, Eu 3+ The physical, electrical, and magnetic properties of doped NFO materials were analyzed using PXRD, FESEM, EDAX, and MPMS techniques. PXRD analysis revealed lower Eu 3+ Substitution (Eu 3+ = 4 and 8) and higher substitutions (Eu 3+ The secondary phase of EuFe2O3 for = 12) was confirmed, and the change in ac showed that spinel lattice positions are responsible for the vacancies of MFe2O4. Furthermore, the higher ionic radius of Eu at positions with lower ionic radii of Fe appears to be due to changes in ac and crystal size. The formation of spherical nanocrystalline grains was revealed by microstructural features, and no evidence of contamination appeared in the EDAX spectrum. The particle size obtained from microstructural analysis is Eu 3+ Due to the high ionic radius of, it increased as ac increased. Magnetic studies at RT and low temperatures showed that at RT, as Eu concentration increased, soft FM behavior and Ms and Mr values ​​increased, and the decrease in RT magnetization was Eu 3+ It undoubtedly shows that this arises from large lattice distortion caused by the distribution of ions and cations at other positions. The decrease in ε' and tan δ indicates Fe at the B site 3+ Eu ions 3+This occurred because the hopping speed decreased as a result of ion substitution. Therefore, rare-earth element-doped ferrite NFO materials are highly useful for various applications in microwave devices and aerospace.

[0165] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will understand that other specific forms can be easily modified without altering the technical spirit or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single unit may be implemented in a distributed manner, and components described as distributed may likewise be implemented in a combined form.

[0166] The scope of the present invention is defined by the claims set forth below, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention.

Claims

Claim 1 Nickel ferrite doped with a rare earth element, comprising a compound of the following chemical formula 1: [Chemical Formula 1]NiMxFe2-xO4, wherein M is a rare earth element and x is greater than 0 Less than 0.12 The number of. The above rare earth element is europium (Eu), and The nickel ferrite doped with the above rare earth element is, Characterized by exhibiting low-loss dielectric properties in which the permittivity (ε′ exhibits dispersion behavior that is high at low frequencies and decreases as frequency increases, and simultaneously the loss coefficient) tan δ decreases in the frequency range of 100 Hz to 2 MHz, Nickel ferrite doped with rare earth elements. Claim 2 delete Claim 3 In claim 1, the nickel ferrite doped with the rare earth element comprises a single-phase FCC crystal structure having an Fm3m space group, and The average grain size of the nickel ferrite nanoparticles doped with the above rare earth elements is, It is 225 nm to 250 nm, and The average crystal size (D) of the nickel ferrite doped with the above rare earth element is, It is 29 nm to 33 nm, and The lattice constant (ac) of the nickel ferrite doped with the above rare earth element is, It is 8.26 Å to 8.30 Å, and The unit cell volume (V) is, Characterized by being 564.4 ų to 573.3 ų, Nickel ferrite doped with rare earth elements. Claim 4 In claim 1, the nickel ferrite doped with the rare earth element has a saturation magnetization (Ms) value 43.15 emu / g to 48.42 emu / g It is a range, and the residual magnetization (Mr) value 23.65 emu / g to 32.64 emu / g It is a range, and the coercivity value 90 Oe to 140 Oe It is a range, and Characterized by exhibiting a soft ferromagnetic hysteresis loop in a temperature range of 10 K to 300 K, and having a right angle ratio (Rs=Mr / Ms) of 0.548 to 0.

674. Nickel ferrite doped with rare earth elements. Claim 5 A method for manufacturing nickel ferrite comprising a combustion reaction by a sol-gel auto-combustion method, The above manufacturing method is, A step of preparing a precursor mixture by mixing Ni(NO3)2.6H2O (nickel nitrate hydrate), Fe(NO3)3.9H2O (iron nitrate hydrate) and a rare earth precursor; to the mixture Citric acid acting as a combustion agent A method for manufacturing nickel ferrite doped with rare earth elements, comprising: a step of preparing a combustion mixture by mixing; a step of obtaining a reproduct by burning the combustion mixture; and a step of forming nickel ferrite doped with rare earth elements by sintering the reproduct. Claim 6 A method for manufacturing nickel ferrite doped with a rare earth element according to claim 5, wherein the nickel ferrite doped with the rare earth element comprises a compound of the following chemical formula 1: [Chemical Formula 1] NiMxFe2-xO4, wherein M is a rare earth element and x is greater than 0 Less than 0.12 Received the commission. Claim 7 In paragraph 5, The above Ni(NO3)2.6H2O (nickel nitrate hydrate), Fe(NO3)3.9H2O (iron nitrate hydrate) In the step of preparing a precursor mixture by mixing rare earth precursors, Ni(NO3)2.6H2O (nickel nitrate hydrate) and Fe(NO3)3.9H2O (ferrous nitrate hydrate) The molar ratio is 1:2, dissolved in deionized water. Stir for 20 minutes A method for manufacturing nickel ferrite doped with rare earth elements. Claim 8 delete Claim 9 delete Claim 10 In paragraph 5, the rare earth precursor comprises a europium precursor, and the europium precursor is Eu(NO3)2.5H2O (europium nitrate hydrate) , method for manufacturing nickel ferrite doped with rare earth elements. Claim 11 delete Claim 12 In paragraph 5, the above mixture citric acid The step of preparing a combustion mixture by mixing the above comprises: in the mixture the citric acid While mixing and stirring 80℃ A method for manufacturing nickel ferrite doped with rare earth elements, wherein the method involves heating. Claim 13 In paragraph 5, the step of obtaining a re-product by burning the combustion mixture is, after igniting the combustion mixture 90 ℃ to 100 ℃ A method for manufacturing nickel ferrite doped with rare earth elements, wherein water is evaporated by heating. Claim 14 In claim 5, the step of sintering the above-mentioned product to form nickel ferrite doped with rare earth elements is Annealing at 800°C for 2 hours at a rate of 7°C , method for manufacturing nickel ferrite doped with rare earth elements.

Images