CN117164354A - Strontium ferrite wave-absorbing material and preparation method and application thereof - Google Patents
Strontium ferrite wave-absorbing material and preparation method and application thereof Download PDFInfo
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- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 title claims abstract description 144
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- DHEQXMRUPNDRPG-UHFFFAOYSA-N strontium nitrate Chemical compound [Sr+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O DHEQXMRUPNDRPG-UHFFFAOYSA-N 0.000 description 26
- 230000000052 comparative effect Effects 0.000 description 19
- QQZMWMKOWKGPQY-UHFFFAOYSA-N cerium(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O QQZMWMKOWKGPQY-UHFFFAOYSA-N 0.000 description 15
- LXXCECZPOWZKLC-UHFFFAOYSA-N praseodymium(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Pr+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O LXXCECZPOWZKLC-UHFFFAOYSA-N 0.000 description 14
- SZQUEWJRBJDHSM-UHFFFAOYSA-N iron(3+);trinitrate;nonahydrate Chemical compound O.O.O.O.O.O.O.O.O.[Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O SZQUEWJRBJDHSM-UHFFFAOYSA-N 0.000 description 13
- IWOUKMZUPDVPGQ-UHFFFAOYSA-N barium nitrate Chemical compound [Ba+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O IWOUKMZUPDVPGQ-UHFFFAOYSA-N 0.000 description 8
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- AJCDFVKYMIUXCR-UHFFFAOYSA-N oxobarium;oxo(oxoferriooxy)iron Chemical compound [Ba]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O.O=[Fe]O[Fe]=O AJCDFVKYMIUXCR-UHFFFAOYSA-N 0.000 description 3
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Abstract
The invention relates to a strontium ferrite wave-absorbing material, a preparation method and application thereof, belonging to the technical field of electromagnetic wave-absorbing materials. The chemical formula of the strontium ferrite wave-absorbing material is as follows: sr (Sr) a Ba b Fe z Pr x Ce y O 19 Wherein a is more than or equal to 0.5 and less than or equal to 1.0, b is more than or equal to 0 and less than or equal to 0.5, z is more than or equal to 10.4 and less than or equal to 11.8,0.1, x is more than or equal to 0.8,0.1 and y is more than or equal to 0.8; the preparation method comprises the following steps: mixing the raw materials, adding water for dissolution, and adding citric acid to form a solution; adjusting the pH, heating and stirring to form wet gel; drying, self-propagating combustion to obtain precursor powder; heating up and calcining, and cooling along with a furnace to obtain the strontium ferrite material. The strontium ferrite wave-absorbing material can cover low, medium and high frequency bands, has wider absorption frequency band, thin absorption thickness and high coercive force and saturation magnetization, meets the requirements of current electronic products on 'thin, light, wide and strong' wave-absorbing materials, and has high application value.
Description
Technical Field
The invention relates to the technical field of electromagnetic wave absorbing materials, in particular to a strontium ferrite wave absorbing material and a preparation method and application thereof.
Background
Under the rapid development of high-tech, the original wave-absorbing material cannot meet the existing development, and the development and the demand of the novel multifunctional wave-absorbing material with light weight, thin thickness, wide absorption frequency band and strong absorption capacity are also urgent.
M-type magnetic lead type strontium ferrite (SrFe) 12 O 19 SFO) is a magnetic material with excellent chemical stability, which restricts its practical application. Meanwhile, the material is a few microwave absorbing materials with magnetic loss and dielectric loss, and has huge wave absorbing potential. And has received much attention for its relatively low price, high saturation Magnetization (MS) capability, high coercivity, high resistivity and corrosion resistance, and excellent chemical stability. However, as a single microwave absorber, the microwave absorber has the defects of high density, low dielectric loss and the like, and limits the practical application.
The improvement of the wave absorbing performance of the M-type ferrite by doping rare earth ions is a research hot spot.Araz synthesizes Ce by adopting ceramic technology 3+ Substituted hexaferrite Ba 1-x Ce X Fe 12 O 19 (x= 0.25,0.5,0.75) ferrite samples. The results show that by Ba 2+ Substitution of Ce at the position 3+ Ions are used for enhancing the magnetic property of the material, and Ce can be obviously improved 3+ The microwave absorption performance of the barium ferrite is replaced. The magnetic dielectric behavior of praseodymium-doped barium ferrite was studied by Karamveer Chahal et al, and the results show that the variation of grain size and grain boundaries under different heat treatments leads to a decrease in the electrical constant and dielectric tangent loss of the praseodymium-doped barium ferrite with increasing calcination temperature. However, the absorption strength and the bandwidth of the ferrite are required to be improved.
Therefore, in order to meet the requirements of current electronic equipment on the characteristics of thinness, lightness, width and strength of the wave-absorbing material, a new strontium ferrite material is developed, the chemical composition of the strontium ferrite material is improved, the preparation process is optimized, the wave-absorbing performance is optimized, the wave-absorbing frequency band width is widened, the wave-absorbing thickness is thinned, and the strontium ferrite material has great application value in the electromagnetic microwave absorption aspect.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a strontium ferrite wave-absorbing material, a preparation method and application thereof. The strontium ferrite wave-absorbing material adopts Pr, ce and Ba elements to be co-doped, and in a specific composition proportion range, pr and Ce can play a synergistic effect, the frequency band width of the wave-absorbing material is widened, the thickness of the material is thinned, and meanwhile, the strontium ferrite wave-absorbing material has high coercive force and high saturation magnetization, meets the requirements of electronic equipment on the thin, light, wide and strong characteristics of the wave-absorbing material, and has wide application prospect.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
in a first aspect, the present invention provides a strontium ferrite wave-absorbing material having the chemical formula: sr (Sr) a Ba b Fe z Pr x Ce y O 19 Wherein a is more than or equal to 0.5 and less than or equal to 1.0, b is more than or equal to 0 and less than or equal to 0.5, z is more than or equal to 10.4 and less than or equal to 11.8,0.1, x is more than or equal to 0.8,0.1 and y is more than or equal to 0.8. The composition of the strontium ferrite wave-absorbing material accords with the mole ratio relation of elements in the chemical formula.
M-type strontium ferrite SrFe as microwave absorbent 12 O 19 Based on the method, ba, pr and Ce are doped into strontium ferrite crystal lattice to play a synergistic effect to change dielectric loss, regulate and control absorption frequency band, widen total absorption bandwidth, remarkably improve microwave absorption performance of the material and reduce cost; the doping amount of Ba, pr and Ce is regulated, so that the saturation magnetization intensity and coercive force can be changed, the magnetostatic performance of the material can be regulated and controlled, and more possibilities are given to the material.
Pr material has high price, while Ce material has low price and rich reserves in China. However, when the Ce element is singly doped, the strontium ferrite material has no wave absorbing effect. Only under the specific Pr-Ce doping amount, the synergistic effect can be exerted, and the wave absorbing effect and the magnetic performance of the ferrite are enhanced. The doped Ce can expand the lattice of the strontium ferrite, enlarge the lattice constant and increase the physical activity; due to the valence variation characteristics (+3 to +4) of Pr and Ce elements, the co-doping is beneficial to the increase of oxygen vacancies and Fe 2+ The generation of the material can realize simultaneous absorption of low, medium and high frequency bands, widen absorption frequency bands, obviously improve dielectric properties of the material and enhance absorption strength of each band. In addition, a certain amount of heterogeneous particles CeO can be generated 2 Extrusion around the M-phase, with interfacial polarization between the M-phase and the out-phase, can increase dielectric loss, also contributing to the wave absorbing effect.
The strontium ferrite wave-absorbing material also introduces Ba. Because the radius of Ba and Sr are close, ba can replace part of Sr to be doped into crystal lattice, the magnetocrystalline anisotropy of the material is reduced, the frequency band width of high-frequency absorption of the material is widened, the frequency band width can reach 4GHz, the corresponding absorption thickness can be as low as 2mm, thereby improving the high-frequency magnetic loss and enhancing the high-frequency wave absorbing effect of the material.
The strontium ferrite wave-absorbing material provided by the invention is spherical polyhedron, has uniform particle size distribution, particle size of 50-800nm, higher coercive force and saturation magnetization intensity, better wave-absorbing performance, wider frequency band width of the wave-absorbing material, thinner wave-absorbing thickness of the material, and wide application prospect, and meets the requirements of electronic equipment on the characteristics of thinness, lightness, width and strength of the wave-absorbing material.
Preferably, in the chemical formula of the strontium ferrite microwave absorbing material, x=y. At this time, strontium ferrite wave absorbing materialThe doping proportion of Pr and Ce in the material is the same, the absorption thickness of the sample is thinner, and the wave absorbing performance is improved: fe at the ratio of 3+ Better transition to Fe 2+ To maintain electrical neutrality in the strontium ferrite; with Fe 2+ The amount of ions increases and Fe appears 3+ And Fe (Fe) 2+ Exchange coupling between ions contributes to new loss factors and increases dielectric loss; in addition, the iron deficiency is beneficial to the generation of oxygen vacancies, causes more vacancy defects and improves the defect polarization rate. When the doping amounts of Pr and Ce are different, the wave-absorbing thickness of the material can be greatly increased, and the practical application of the material in electronic products is not facilitated.
Further preferably, in the chemical formula of the strontium ferrite yet another material, z is 11.5.ltoreq. 11.8,0.1.ltoreq.x=y.ltoreq.0.25. Under the Pr-Ce doping of the chemical formula proportion, the strongest absorption of the strontium ferrite wave-absorbing material is between-31.61 and-43.51 dB, the corresponding thinnest absorption thickness is between 2 and 2.5mm, the wave-absorbing strength is good, the material thickness is thin, and the comprehensive wave-absorbing performance is strong. The co-doping proportion of Pr-Ce is continuously increased, and the wave absorbing performance of the strontium ferrite wave absorbing material is poor.
Further preferably, in the chemical formula of the strontium ferrite yet another material, z=11.7 and x=y=0.15. When the contents of Fe, pr and Ce in the strontium ferrite wave-absorbing material accord with the chemical formula molar ratio, pr and Ce can play a synergistic effect, and the low, medium and high frequency simultaneous absorption and wide coverage range are realized under the lower doping amount, so that the wave-absorbing frequency is widened to be more than 4GHz, the thickness of the material is reduced to be 2-2.5mm, and the overall wave-absorbing performance is improved; meanwhile, the saturation magnetization intensity can reach more than 70emu/g, the coercive force is more than 4400Oe, the magnetic property is good, and the comprehensive effect is obviously superior to that of a strontium ferrite material doped with a single element under the same doping amount. The Pr-Ce doping amount is increased or decreased, the coverage area of the material wave-absorbing frequency band is narrowed, and the thinnest absorption is thickened.
In a second aspect, the invention provides a preparation method of the strontium ferrite microwave absorbing material, which comprises the following steps:
(1) Mixing a strontium source, a barium source, an iron source, a praseodymium source, a cerium source, a complexing agent and a solvent to obtain a mixed solution;
(2) Regulating the pH value of the mixed solution obtained in the step (1) to 6-8, and heating and stirring at 80-105 ℃ to form wet gel;
(3) Drying the wet gel obtained in the step (2) at 105-120 ℃, and then self-propagating combustion to obtain precursor powder;
(4) And (3) heating the precursor powder in the step (3) to 1100-1260 ℃ for calcination, preserving heat for 4-10h, and cooling to room temperature along with a furnace to obtain the strontium ferrite wave-absorbing material.
The proportion of the strontium source, the barium source, the iron source, the praseodymium source and the cerium source is according to the molar ratio of metal elements in the chemical formula of the strontium ferrite wave-absorbing material. Adding complexing agent, regulating pH value to 6-8, stirring at 80-105deg.C, and mixing metal ions in barium source, strontium source, iron source, praseodymium source and cerium source with complexing agent to form stable gel, so that each metal ion is distributed in gel network structure.
If heating and uneven mixing are not performed, metal ions cannot be fully dispersed, partial particles are easy to agglomerate, and the wave absorbing effect is poor; without adjusting the pH value, the solution is acidic, metal ions cannot be closely distributed, and the formed ferrite particles are loose and have poor wave absorbing effect.
Firstly drying, synthesizing a precursor through self-propagating combustion, primarily converting each metal ion into metal oxide and solid metal salt, improving conversion rate and product purity, and saving energy consumption; the precursor is calcined for 4-10 hours at 1100-1260 ℃, so that each phase is further interacted to react at high temperature to remove impurities, and the prepared strontium ferrite wave-absorbing material has good wave-absorbing effect and uniform and compact structural arrangement.
The preparation method has the advantages of low production cost, simple process, low energy consumption, no environmental pollutants, high conversion rate, good dispersibility of the prepared wave-absorbing material, adjustable wave-absorbing frequency band, high wave-absorbing strength, high working temperature and the like.
Preferably, the ratio of the total molar amount of strontium source, barium source, iron source, praseodymium source, cerium source to the molar amount of complexing agent is 1:1, a step of; the complexing agent is citric acid. The strontium source, the barium source, the iron source, the praseodymium source and the cerium source are soluble salts of various metal elements; when the mole amount of the citric acid serving as the complexing agent is equal to the total mole amount of each metal ion, the citric acid can just fully carry out hydrolysis and polycondensation reaction with the metal ion after heating, and uniform and fluffy xerogel is generated after drying, so that the strontium ferrite with moderate particle size and good wave absorbing performance can be prepared.
Preferably, the conditions for self-propagating combustion are: reacting at 200-250deg.C for 6-12min. The dried gel is ignited under the condition, self-propagating combustion reaction occurs in a short time to obtain fluffy coral brown powder, and the powder is ground into fine and uniform particles to obtain a precursor. The heat released by the chemical reaction is utilized to continuously and rapidly complete the combustion reaction, a high-temperature heat source is not needed, the energy consumption is saved, the operation is simple and convenient, the complexing agent in the gel is removed, and the conversion rate is high and the speed is high.
Preferably, the rate of temperature rise is 4-6deg.C/min. Under the heating rate, the growth time of the formed crystal particles is controlled, and crystal grains with the size of nanometer are obtained, so that the strontium ferrite structure is more compact in arrangement, large in coercive force, high in dielectric loss and better in wave absorbing effect.
Preferably, the temperature is raised to 600 ℃, the temperature is kept for 2 hours, and the temperature is raised to the calcination temperature. Setting an intermediate temperature: gamma-Fe at 600 °c 2 O 3 Phase formation of SrCO 3 Reaction of SrO to spinel SrFe 2 O 4 And then continue to react with gamma-Fe 2 O 3 Phase interaction to form SrFe 12 O 19 And release CO 2 Preserving heat for 2h at the temperature to ensure SrCO 3 Fully decomposed to ensure that strontium ferrite matrix particles grow steadily and uniformly, so that doping elements enter crystal lattices to continue to react when the temperature is continuously increased and calcined. As the crystals are fully grown, the resistivity among grain boundaries is reduced, so that the dielectric loss is increased, the wave absorption frequency band is wider, and the effect is better.
In the third aspect, the strontium ferrite wave-absorbing material provided by the invention has the advantages of wave-absorbing bandwidth, thin wave-absorbing thickness, high coercive force and high saturation magnetization, meets the requirements of electronic equipment on the characteristics of thinness, lightness, width and strength of the wave-absorbing material, and has wide application prospect.
Compared with the prior art, the invention has the beneficial effects that:
the strontium ferrite is prepared by co-doping Pr, ce and Ba elements, so that the cost is low, the preparation energy consumption is low, pr-Ce can play a synergistic effect within a specific proportioning range, the frequency band width of the wave-absorbing material is widened, the thickness of the material is thinned, the wave-absorbing effect is good, the coercive force is large, the saturation magnetization intensity is high, the working temperature is high, the requirements of electronic equipment on the thin, light, wide and strong characteristics of the wave-absorbing material are met, and the application prospect is wide.
Drawings
FIG. 1 is a 1 μm-scale SEM image of a strontium ferrite microwave absorbing material of example 1;
FIG. 2 is a 500 nm-scale SEM image of a strontium ferrite microwave absorbing material of example 1;
FIG. 3 is a graph showing the wave-absorbing effect of the strontium ferrite wave-absorbing material of example 1;
FIG. 4 is a 1 μm-scale SEM image of the strontium ferrite microwave absorbing material of example 2;
FIG. 5 is a 500 nm-scale SEM image of a strontium ferrite microwave absorbing material of example 2;
FIG. 6 is a graph showing the wave-absorbing effect of the strontium ferrite wave-absorbing material of example 2;
FIG. 7 is a 1 μm-scale SEM image of the strontium ferrite microwave absorbing material of example 3;
FIG. 8 is a 500 nm-scale SEM image of a strontium ferrite microwave absorbing material of example 3;
fig. 9 is a graph showing the wave-absorbing effect of the strontium ferrite wave-absorbing material of example 3.
Detailed Description
For a better description of the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to the following specific examples. The test methods used in the following examples are conventional methods unless otherwise specified; the materials, reagents and the like used, unless otherwise specified, are those commercially available.
In the following examples and comparative examples, the test modes of the wave-absorbing performance parameters of the strontium ferrite materials are as follows:
a vector network analyzer model N5224B from Keysight corporation was used to measure electromagnetic parameters of the material. The powder sample is prepared into a special test ring, and the test ring is prepared by uniformly mixing samples with paraffin in different proportions and tabletting. The test ring was prepared as follows: grinding the strontium ferrite wave-absorbing material in a mortar to obtain powder to be measured, and mixing paraffin with the powder to be measured according to a mass ratio of 3:7, adding the mixture into a proper amount of n-hexane, and performing ultrasonic dispersion to uniformly mix the powder with paraffin. After the n-hexane had evaporated, a dried sample was obtained and placed in a mold and pressed into a test ring. The test frequency is 2-18GHz, the dynamic electromagnetic parameters are measured by adopting a coaxial method, and the reflection losses with different thicknesses are calculated.
In the following examples and comparative examples, the magnetic properties of the strontium ferrite materials were tested in the following manner: a magnetic measurement system, model MPMS3, was used to measure the magnetic properties of the material.
In the following examples and comparative examples, the particle size of the strontium ferrite materials was measured in the following manner: the microscopic appearance of the material is observed by adopting a high-resolution field emission scanning electron microscope with the model of [ JSM-IT800], and the equipment is also provided with an energy spectrum analyzer for carrying out element analysis on the surface of the material.
Example 1
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 11.7 Pr 0.15 Ce 0.15 O 19 。
The preparation method of the strontium ferrite microwave absorbing material comprises the following steps:
(1) The molar ratio is 1:11.7:0.15:0.15 raw materials of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, cerium nitrate hexahydrate and deionized water are stirred and mixed, and then citric acid monohydrate aqueous solution is added, wherein the molar quantity ratio of citric acid to the total molar quantity ratio of metal salt is 1:1, stirring for 4 hours to obtain a mixed solution;
(2) Dropwise adding 25% ammonia water into the mixed solution until the pH value of the mixed solution is 7, and then placing the mixed solution into an oil bath constant temperature tank, and stirring at a constant temperature of 90 ℃ for 9 hours to obtain viscous gel;
(3) Drying the viscous gel in a forced air drying oven at 105 ℃ for 5 hours, performing self-propagating combustion at 200 ℃ for 12 minutes to obtain powder, and grinding to obtain a precursor;
(4) And heating the precursor powder to 1100 ℃ at a heating rate of 5 ℃/min, calcining and preserving heat for 4 hours, and cooling to room temperature along with a furnace to obtain the strontium ferrite wave-absorbing material.
Fig. 1-2 are SEM pictures of the strontium ferrite microwave absorbing material of the present embodiment. The graph shows that the particle size of the wave-absorbing material is 50-200nm, and the wave-absorbing material has a polyhedral structure and is closely and uniformly distributed.
FIG. 3 is a graph showing the measured wave absorbing effect, wherein the strontium ferrite wave absorbing material has strong absorption at both low frequency and high frequency bands, the strongest absorption reaches-31.61 dB, the matching thickness is 5.5mm, and the wave absorbing frequency is as wide as 4.13GHz; the thinnest absorption reaches 2.5mm, the corresponding absorption frequency band is the medium frequency, and the wave absorbing effect is good in each frequency band.
Example 2
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 11.8 Pr 0.1 Ce 0.1 O 19 。
The preparation method of the strontium ferrite microwave absorbing material in the embodiment 2 is different from that in the embodiment 1 in that the mole ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate and cerium nitrate hexahydrate is 1:11.8:0.1:0.1, self-propagating combustion is carried out at 250 ℃ for 6min, calcination is carried out for 6h, and the rest steps are the same as in example 1.
Fig. 4 to 5 are SEM pictures of the strontium ferrite microwave absorbing material of the present embodiment. The graph shows that the particle size of the wave-absorbing material is 50-200nm, and the wave-absorbing material has a polyhedral structure and is closely and uniformly distributed.
FIG. 6 is a graph of the measured wave absorbing effect, wherein the strontium ferrite wave absorbing material has strong absorption at both low frequency and high frequency bands, the strongest absorption reaches-43.51 dB, the matching thickness is 5.5mm, and the wave absorbing frequency is 3.79GHz wide; the thinnest absorption reaches 2.5mm, the corresponding absorption frequency band is low frequency, and the wave absorbing effect is good.
Example 3
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 11.5 Pr 0.25 Ce 0.25 O 19 。
Example 3 the method for preparing the strontium ferrite microwave absorbing material is different from example 1 in that the mole ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate and cerium nitrate hexahydrate is 1:11.5:0.25:0.25, self-propagating combustion is carried out for 10min at 220 ℃, calcination is carried out for 8h, and the rest steps are the same as in example 1.
Fig. 7 to 8 are SEM pictures of the strontium ferrite microwave absorbing material of the present embodiment. The graph shows that the particle size of the wave-absorbing material is 50-200nm, and the wave-absorbing material has a polyhedral structure and is closely and uniformly distributed.
FIG. 9 is a graph of the measured wave absorbing effect, wherein the strontium ferrite wave absorbing material has strong absorption at both low frequency and high frequency bands, the strongest absorption reaches-43.95 dB, the matching thickness is 5.5mm, and the wave absorbing frequency is 3.52GHz wide; the thinnest absorption reaches 2.5mm, the corresponding absorption frequency band is low frequency, and the wave absorbing effect is good.
Example 4
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 11 Pr 0.5 Ce 0.5 O 19 。
Example 4 the method for preparing the strontium ferrite microwave absorbing material is different from example 1 in that the mole ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate and cerium nitrate hexahydrate is 1:11:0.5:0.5, adjusting the pH of the sol to 6, stirring at a constant temperature of 80 ℃ to form wet gel, drying at 110 ℃, and the rest of the steps are the same as in example 1. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 5
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 10.8 Pr 0.6 Ce 0.6 O 19 。
Example 5 the method for preparing the strontium ferrite microwave absorbing material is different from example 1 in that the mole ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate and cerium nitrate hexahydrate is 1:10.8:0.6:0.6, adjusting the pH of the sol to 8, stirring at a constant temperature of 105 ℃ to form wet gel, drying at 120 ℃, and the rest of the steps are the same as in example 1. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 6
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 11.5 Pr 0.3 Ce 0.2 O 19 。
Example 6 the method for preparing the strontium ferrite microwave absorbing material is different from example 1 in that the mole ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate and cerium nitrate hexahydrate is 1:11.5:0.3:0.2, heating to 1100 ℃ at a heating rate of 4 ℃/min, calcining and preserving heat for 10 hours, and the rest steps are the same as in the example 1. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 7
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 11.5 Pr 0.4 Ce 0.1 O 19 。
Example 7 the method for preparing the strontium ferrite microwave absorbing material is different from example 1 in that the mole ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate and cerium nitrate hexahydrate is 1:11.5:0.4:0.1, heating to 1260 ℃ at a heating rate of 6 ℃/min, calcining and preserving heat for 6 hours, and the rest steps are the same as in the example 1. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 8
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 11.7 Pr 0.15 Ce 0.15 O 19 。
Example 8 the process for preparing the strontium ferrite microwave absorbing material is different from example 1 in that the temperature is raised to 1200 ℃ for calcination, and the rest steps are the same as in example 1. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 9
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 11.7 Pr 0.15 Ce 0.15 O 19 。
The preparation method of the strontium ferrite microwave absorbing material in the embodiment 9 is different from the preparation method in the embodiment 1 in that the temperature is raised to 600 ℃ for 2 hours, the temperature is continuously raised to 1260 ℃ for 10 hours, and the rest steps are the same as the embodiment 1. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 10
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 11.4 Pr 0.3 Ce 0.3 O 19 。
The preparation method of the strontium ferrite microwave absorbing material of example 10 is different from that of example 9 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate and cerium nitrate hexahydrate is 1:11.4:0.3:0.3, the rest of the procedure is the same as in example 9. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 11
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 11.2 Pr 0.4 Ce 0.4 O 19 。
The preparation method of the strontium ferrite microwave absorbing material of example 11 is different from that of example 9 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate and cerium nitrate hexahydrate is 1:11.2:0.4:0.4, the rest of the procedure is the same as in example 9. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 12
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 11 Pr 0.5 Ce 0.5 O 19 。
The preparation method of the strontium ferrite microwave absorbing material of example 12 is different from that of example 4 in that the temperature is raised to 600 ℃ and kept for 2 hours, the temperature is continuously raised to 1260 ℃ and kept for 10 hours, and the rest steps are the same as those of example 4. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 13
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 10.8 Pr 0.6 Ce 0.6 O 19 。
The preparation method of the strontium ferrite microwave absorbing material of example 13 is different from that of example 5 in that the temperature is raised to 600 ℃ and kept for 2 hours, the temperature is continuously raised to 1260 ℃ and kept for 10 hours, and the rest steps are the same as those of example 5. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 14
An embodiment of the strontium ferrite wave-absorbing material of the present invention is SrFe 10.4 Pr 0.8 Ce 0.8 O 19 。
The preparation method of the strontium ferrite microwave absorbing material of example 14 is different from that of example 9 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate and cerium nitrate hexahydrate is 1:10.4:0.8:0.8, the rest of the procedure is the same as in example 9. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 15
An embodiment of the strontium ferrite wave-absorbing material of the present invention is Sr 0.5 Ba 0.5 Fe 11.7 Pr 0.15 Ce 0.15 O 19 。
The preparation method of the strontium ferrite microwave absorbing material of embodiment 15 is different from that of embodiment 9 in that the raw materials further comprise barium nitrate, strontium nitrate, barium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate and cerium nitrate hexahydrate with a molar ratio of 0.5:0.5:11.7:0.15:0.15, and the rest of the procedure was the same as in example 9. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 16
An embodiment of the strontium ferrite wave-absorbing material of the present invention is Sr 0.75 Ba 0.25 Fe 11.7 Pr 0.15 Ce 0.15 O 19 。
The preparation method of the strontium ferrite microwave absorbing material of embodiment 16 is different from that of embodiment 9 in that the raw materials further comprise barium nitrate, strontium nitrate, barium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate and cerium nitrate hexahydrate with a molar ratio of 0.75:0.25:11.7:0.15:0.15, and the rest of the procedure was the same as in example 9. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Example 17
An embodiment of the strontium ferrite wave-absorbing material of the present invention is Sr 0.85 Fe 11.85 Pr 0.15 Ce 0.15 O 19 。
The preparation method of the strontium ferrite microwave absorbing material of example 17 is different from that of example 9 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate and cerium nitrate hexahydrate is 0.85:11.85:0.15:0.15, and the rest of the procedure was the same as in example 9. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the embodiment are shown in table 1; the particle size and magnetic properties parameters are shown in Table 2.
Comparative example 1
Comparative example 1 a strontium ferrite microwave absorbing material was prepared in the same manner as in example 1 except that praseodymium nitrate and cerium nitrate hexahydrate were not added. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the comparative example are shown in Table 1; the particle size and magnetic properties parameters are shown in Table 2.
Comparative example 2
The preparation method of the strontium ferrite microwave absorbing material of comparative example 2 is different from that of example 1 in that praseodymium nitrate is not added, and the other steps are the same as those of example 1. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the comparative example are shown in Table 1; the particle size and magnetic properties parameters are shown in Table 2.
Comparative example 3
Comparative example 3 a strontium ferrite microwave absorbing material was prepared in the same manner as in example 1 except that cerium nitrate hexahydrate was not added. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the comparative example are shown in Table 1; the particle size and magnetic properties parameters are shown in Table 2.
Comparative example 4
The comparative example 4 strontium ferrite microwave absorbing material was prepared by the same method as in example 14, except that the sample was not heated and stirred at constant temperature after the pH was adjusted, but was placed in a dry box and left to stand at constant temperature to perform sol-gel reaction to obtain a viscous gel, and the other steps were the same as in example 1. The wave-absorbing performance parameters of the strontium ferrite wave-absorbing material in the comparative example are shown in Table 1; the particle size and magnetic properties parameters are shown in Table 2.
The chemical formulas and the wave-absorbing performance parameters of the strontium ferrite wave-absorbing materials in the above examples 1 to 17 and comparative examples 1 to 4 are shown in Table 1; the particle size and magnetic properties of the strontium ferrite microwave absorbing materials in examples 1 to 9 and comparative examples 1 to 3 are shown in Table 2.
TABLE 1
TABLE 2
From the results of tables 1 and 2, the following points can be found:
(1) As can be seen from examples 1-17, the strontium ferrite wave-absorbing material of the invention has better wave-absorbing performance, has certain wave-absorbing effect in low, middle and high frequency bands, has a thin frequency band width and thickness, has high coercive force and saturation magnetization intensity, and meets the characteristic requirements of 'thin, light, wide and strong' wave-absorbing materials at present.
(2) Examples 3, 6, 7 show that when the molar ratio of Pr to Ce is 1:1, the thickness of the strontium ferrite wave-absorbing material is obviously reduced, the better wave-absorbing strength is maintained, and the strontium ferrite wave-absorbing material is more suitable for the practical application of electronic products.
(3) In the chemical formula of the strontium ferrite wave-absorbing material, when z is more than or equal to 11.5 and less than or equal to 11.8,0.1 and x=y and less than or equal to 0.25, under Pr-Ce doping of the chemical formula proportion, the wave-absorbing frequency band is wider and can reach more than 4GHz, the absorption frequency band is the widest, the strontium ferrite wave-absorbing material has stronger absorption at low, middle and high frequencies, the corresponding material thickness is thin, the saturation magnetization and the coercive force are higher, and the overall wave-absorbing performance and the magnetic performance are better.
(4) As can be seen from the comparison of the example 1 and the comparative examples 1-3, the undoped strontium ferrite has higher natural resonance frequency, has self-limitation and poor wave absorbing effect; the microwave absorbing effect is not generated when only Ce is doped; the wave absorbing strength is weaker when only Pr is doped; when Pr-Ce is co-doped in equal amount, the wave-absorbing strength is obviously improved, the corresponding material thickness is thin, and each frequency band of low, medium and high has a certain wave-absorbing effect, and the comprehensive wave-absorbing performance is good. It is known that the single element doped sample has less wave absorption loss mechanism, which is unfavorable for oxygen vacancy and Fe 2+ The wave absorbing thickness is thicker, the absorbing width is narrower, and the wave absorbing performance is poor; and in the chemical formula, when z=11.7 and x=y=0.15, the co-doping of Pr-Ce can reduce the cost, exert better synergistic effect, obviously improve the wave-absorbing performance, widen the wave-absorbing coverage frequency band and frequency band width, reduce the material thickness and be more suitable for the practical application of wave-absorbing materials.
(5) As can be seen from comparison of example 9 with examples 15 and 16, the introduction of Ba is beneficial to reducing magnetocrystalline anisotropy of the material, and widening wave absorption width of the strontium ferrite wave absorption material in a high frequency band, which can reach 4.05GHz; meanwhile, the thickness of the corresponding material is reduced to 2mm, which is beneficial to improving the high-frequency magnetic loss.
(6) As is clear from a comparison of example 17 and example 9, the wave absorbing effect is more effective in a specific strontium ferrite matrix proportioning environmentAnd (3) good: pr-Ce can be better interacted and doped into crystal lattice, and partial Ce can be separated out of CeO 2 Heterogeneous particles, distributed around the M phase, undergo interfacial polarization, thereby increasing dielectric losses.
(7) Examples 9-13 set up optimized calcination process. Examples 12, 13 are compared with examples 4, 5: when other conditions are unchanged, the intermediate temperature is set at 600 ℃, the heat preservation time is prolonged, the resistivity among grain boundaries is reduced, the dielectric loss is increased, the wave absorption strength of the material is obviously enhanced, and the wave absorption frequency band is widened.
(8) As is clear from the comparison between example 14 and comparative example 4, when the xerogel is obtained by standing without stirring at a constant temperature, the molecules are not sufficiently mixed, and some particles are easily agglomerated, resulting in poor wave absorbing effect.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted equally without departing from the spirit and scope of the technical solution of the present invention.
Claims (10)
1. The strontium ferrite wave-absorbing material is characterized by comprising the following chemical formula: sr (Sr) a Ba b Fe z Pr x Ce y O 19 Wherein a is more than or equal to 0.5 and less than or equal to 1.0, b is more than or equal to 0 and less than or equal to 0.5, z is more than or equal to 10.4 and less than or equal to 11.8,0.1, x is more than or equal to 0.8,0.1 and y is more than or equal to 0.8.
2. The strontium ferrite microwave absorbing material of claim 1, wherein x = y in the chemical formula of the strontium ferrite microwave absorbing material.
3. The strontium ferrite microwave absorbing material according to claim 2, wherein in the chemical formula of the strontium ferrite microwave absorbing material, 11.5.ltoreq.z.ltoreq. 11.8,0.1.ltoreq.x=y.ltoreq.0.25.
4. A strontium ferrite microwave absorbing material according to claim 3, wherein in the formula of the strontium ferrite microwave absorbing material, z=11.7 and x=y=0.15.
5. The method for producing a strontium ferrite microwave absorbing material according to any of claims 1 to 4, comprising the steps of:
(1) Mixing a strontium source, a barium source, an iron source, a praseodymium source, a cerium source, a complexing agent and a solvent to obtain a mixed solution;
(2) Regulating the pH value of the mixed solution obtained in the step (1) to 6-8, and heating and stirring at 80-105 ℃ to form wet gel;
(3) Drying the wet gel obtained in the step (2) at 105-120 ℃, and then self-propagating combustion to obtain precursor powder;
(4) And (3) heating the precursor powder in the step (3) to 1100-1260 ℃ for calcination, preserving heat for 4-10h, and cooling to room temperature along with a furnace to obtain the strontium ferrite wave-absorbing material.
6. The method of claim 5, wherein in the step (1), the ratio of the total molar amount of the strontium source, the barium source, the iron source, the praseodymium source, and the cerium source to the molar amount of the complexing agent is 1:1, a step of; preferably, the complexing agent is citric acid.
7. The method for preparing a strontium ferrite microwave absorbing material according to claim 5, wherein in the step (3), the self-propagating combustion condition is: reacting at 200-250deg.C for 6-12min.
8. The method of claim 5, wherein in the step (4), the heating rate is 4-6 ℃/min.
9. The method of claim 5, wherein in step (4), the temperature is raised to 600 ℃ and maintained for 2 hours, and then the calcination temperature is raised.
10. Use of the strontium ferrite microwave absorbing material according to claim 1 in electromagnetic microwave absorption of electronic equipment.
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