Wave-band-adjustable perovskite wave-absorbing material and preparation method thereof

Abstract

The invention provides a perovskite wave-absorbing material and a preparation method thereof, and relates to the technical field of microwave absorbing materials. The molecular formula of the perovskite wave-absorbing material is (La1-xMnx) Mn1-yFeyCozO3 wave-absorbing material, x is more than or equal to 0 and less than or equal to 0.4, y is equal to 0.4, z is more than or equal to 0 and less than or equal to 0.4, and the perovskite wave-absorbing material is obtained by carrying out gelation reaction on metal nitrate and citric acid and then pre-sintering and calcining. According to the preparation method, the defects in the prior art are overcome, the C wave band (4-8 GHz) and the Ku wave band (12-18 GHz) of the prepared wave absorbing material are adjustable, the wave absorbing material has a wide effective absorption band and excellent absorption efficiency and has application prospects in the fields of magnetics and microwave absorption, and the whole preparation process is simple in technology and suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave absorbing materials, and in particular to a perovskite absorbing material with adjustable wavelength and a preparation method thereof. Background Art

[0002] With the widespread adoption of radar, electronic, and wireless devices, electromagnetic radiation pollution and compatibility issues are becoming increasingly severe. The development of high-performance electromagnetic wave absorbing materials has become crucial for electromagnetic shielding. Lanthanum manganese perovskite oxide (LaMnO3) has attracted considerable attention among potential electromagnetic wave absorbing materials due to its unique crystal structure and mixed ionic and electronic conductivity. However, LaMnO3 as an electromagnetic wave absorbing material currently suffers from poor dielectric constant and impedance matching, weak absorption intensity (absorption intensity <90%), limited absorption bandwidth (the width of absorption intensity <-10 dB is less than 2 GHz), and excessively high absorption frequency (>15 GHz), making it difficult to meet the requirements for tunable absorption performance in the C-band (4-8 GHz) and Ku-band (12-18 GHz).

[0003] Huang et al. [J Magn Magn Mater, 2012, 324(19): 3149-3153] prepared La by sol-gel method. 0.85 Ag 0.15 MnO3 perovskite oxide material, in which magnetic loss and dielectric loss coexist and work together to achieve effective attenuation of microwaves. The bandwidth is less than -10 dB at around 6 GHz, and the reflection loss peak is close to -25.0 dB when the layer thickness is 2 mm.

[0004] Jia et al. [Compos Part B-Eng, 2019, 176: 107246] used K + La doping 1-x K x MnO3, when x=0.3, the minimum reflection loss reaches -27.1 dB at a sample thickness of 2.40 mm, and the effective absorption bandwidth is 10.6 GHz.

[0005] Wang et al. [Mat Sci Semicon Proc, 2014, 19: 101-106] studied the effect of iron addition on La 0.7 Sr 0.3 MnO 3±δ The electromagnetic and microwave absorption properties of the material are affected by the Fe content. When the Fe content is 0.12, the material achieves broadband absorption below -8 dB in the 8.5 GHz frequency band.

[0006] Fauziyah et al. [J Phys: Conference Series, 2018, 983: 012019] prepared Ni-doped (Ni=0.05) La 0.67 Sr 0.33 The incorporation of MnO3 and Ni reduces the lattice constant of the sample, and the minimum reflection loss is -6.29 dB at 11.47 GHz.

[0007] Mu et al. [Nano Research, 2022, 15(8): 7731-7741] studied the A-site Sr 2+ and B-site Fe 3+ Co-doping of La 1-x Sr x Mn 1-y Fe y The influence of O3 on the absorption performance, La 0.7 Sr 0.3 Mn 0.8 Fe 0.2 When the thickness of O3 / MAS is only 1.9 mm, it can achieve the widest bandwidth of 4.2 GHz covering the entire X-band (8.2-12.4 GHz) and the minimum reflection loss value of -17.99 dB at 500 °C.

[0008] CN102020974B discloses a carbonyl iron powder / lanthanum strontium manganate composite material and a preparation method thereof. The composite material is composed of carbonyl iron powder and La 1-x Sr x It is composed of a mixed MnO3 powder with a thickness of less than 1 mm, and can evenly and effectively absorb electromagnetic waves in the 8-12 GHz frequency band.

[0009] CN108541206A discloses a band-adjustable resistive film type high-temperature metamaterial absorber (La x Sr 1-x MnO3) material, the value range of x in its chemical formula is 0.5<x<0.9, and its absorption band is adjustable in the X band (8-12 GHz) and Ku band (12-18 GHz).

[0010] CN107141021A discloses an X-band resistive film type high temperature metamaterial absorber by changing La 1- x Sr xBy adjusting the x value (0.5≤x<1) of the element doping amount in the MnO3 powder, the square resistance of the resistance film of the metamaterial absorber is changed, so that the absorber's absorbing efficiency exists in the entire X-band of 8-12 GHz. The maximum absorption intensity of the absorber and the frequency position where the maximum absorption intensity occurs can be further optimized according to application needs.

[0011] CN118754638A discloses a high-performance absorbing material and its preparation method. The molecular formula of the perovskite absorbing material is LaMn 1-x Fe x O3 absorbing material, where 0.1≤x≤0.5. Its absorption band is the Ku band (12-18 GHz). When x=0.4 and thickness d=2.0 mm, the minimum reflection loss is -54.99 dB, and the effective absorption bandwidth is 4.56 GHz. Summary of the Invention

[0012] On the one hand, the present invention aims to provide a band-tunable perovskite absorber material that can achieve adjustable absorption performance in the C-band (4-8 GHz) and Ku-band (12-18 GHz), with high absorption intensity and a wide effective absorption bandwidth in the C-band and Ku-band. On the other hand, the present invention aims to provide a method for preparing the band-tunable perovskite absorber material described above.

[0013] To achieve the above objectives, the technical solution of the present invention is implemented through the following technical solutions: A band-adjustable perovskite absorbing material, characterized in that the absorbing material is a perovskite structure, and its chemical composition formula is (La 1-x Mn x )Mn 1-y Fe y Co z O3 absorbing material, where x, y, and z are molar coefficients, 0≤x≤0.4, y=0.4, 0≤z≤0.4; Adjustable absorption performance in the Ku band (12-18 GHz), preferably, 0≤x≤0.4, y=0.4, z=0; Adjustable absorption performance in C band (4-8 GHz), preferably, x=0.3, y=0.4, 0 <z≤0.4; On the other hand, the present invention also provides a method for preparing the perovskite absorbing material with adjustable wavelength as described above, comprising the following steps: According to the chemical composition formula (La 1-x Mn x )Mn 1-y Fe y Co zC6H9O6La, Fe(NO3)3·9H2O, Mn(NO3)3·6H2O, C6H8O7 and NH3·H2O were weighed and placed in a beaker according to the values of the molar coefficients x and y of O3; Co(NO3)2·9H2O was weighed according to the value of the molar coefficient z and placed in the above beaker, and the mixture was dissolved in 25 mL of distilled water, maintaining a molar ratio of citric acid to metal ions of 1:1, and stirred for 0.5 h; the resulting solution was heated and stirred at 80 °C for 4 h to induce sol formation; the sol was then dried in an air drying oven at 180 °C for 1 h to obtain a precursor; finally, the precursor was heated to 900 °C at a heating rate of 1 °C / min and calcined for 8 h to obtain the perovskite absorber material.

[0014] The present invention provides a perovskite absorbing material with adjustable wavelength and a preparation method thereof, which has the following advantages over the prior art: On the one hand, by adjusting the molar coefficient x value, Mn is introduced into the A site (La 3+ ) to form Mn 3+ / Mn 4+ , by inducing the generation of oxygen vacancies through charge imbalance, thereby enhancing space charge polarization and increasing dielectric loss; A-site Mn and B-site Fe / Mn form a Mn(A-site)-O-Mn / Fe(B-site) superexchange network, which optimizes the imaginary part of magnetic permeability by adjusting the ferromagnetic coupling strength; A-site Mn doping can reduce material density and increase interface scattering, improve impedance matching characteristics, reduce electromagnetic wave reflection, and achieve synergistic enhancement of dielectric-magnetic loss. On the other hand, by adjusting the molar coefficient z value, excessive Co is doped into the B-site, resulting in the precipitation of Fe3O4 spinel phase, forming a perovskite oxide-spinel heterostructure, and Fe3O4 interacts with the perovskite matrix to form a magnetic coupling network, which promotes the interaction and energy transfer of magnetic domains, and significantly increases the magnetic loss; at the same time, Co 3+ The pinning effect restricts the movement of the magnetic domain wall, reduces the generation of induced current, and thus reduces eddy current loss; the state of multi-phase coexistence can effectively reduce the absorption peak position through multiple relaxation (dielectric) and multi-resonance peak (magnetic) mechanisms, thereby achieving the effect of low-frequency microwave absorption of perovskite oxide.

[0015] The perovskite absorbing material of the present invention can achieve adjustable absorbing performance in the C band (4-8 GHz) and the Ku band (12-18 GHz), and has high absorption intensity in the C band and the Ku band, and a wide effective absorption bandwidth. For example, at 14.64 GHz in the Ku band and d = 2.0 mm, the minimum reflection loss is -28.09 dB, and the widest effective absorption bandwidth is 6.08 GHz; at 6.48 GHz in the C band and d=4.5 mm, the minimum reflection loss is -51.44 dB, and the widest effective absorption bandwidth is 2.64 GHz. The present invention also provides a method for preparing the perovskite absorber material, which can be obtained through a sol-gel reaction, pre-sintering, and calcination. The entire preparation process has excellent process stability, low cost, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the X-ray diffraction pattern of the perovskite powder prepared in this embodiment of the present invention.

[0017] Figure 2 These are SEM images of the sample with x=0.3, y=0.4, z=0 in Example 1 of the present invention and the sample with x=0.3, y=0.4, z=0.2 in Example 2.

[0018] Figure 3 This is the XPS graph of the perovskite powder prepared in an embodiment of the present invention.

[0019] Figure 4 MH diagram of the perovskite powder prepared in an embodiment of the present invention.

[0020] Figure 5 This is a reflection loss diagram of the perovskite ring prepared in an embodiment of the present invention at different thicknesses.

[0021] Figure 6 This is the impedance matching diagram of the ring sample prepared in an embodiment of the present invention.

[0022] Figure 7 This is a performance diagram of the effective absorption bandwidth of the ring sample prepared in an embodiment of the present invention.

[0023] Figure 8 This is a data diagram of the wave absorption performance of the ring sample prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] Example 1

[0026] (1) According to the molecular formula (La 1-x Mn x )Mn 1-y Fe y Co zO3, where 0 ≤ x ≤ 0.4, y = 0.4, z = 0. Five groups of raw materials were weighed respectively (Group 1: 1.575 g of C6H9O6La, 1.047 g of Mn(NO3)3·6H2O, 0.808 g of Fe(NO3)3·9H2O; Group 2: 1.418 g of C6H9O6La, 1.222 g of Mn(NO3)3·6H2O, 0.808 g of Fe(NO3)3·9H2O; Group 3: 1.260 g of C6H9O6La, 1.396 g of Mn(NO3)3·6H2O, 0.808 g of Fe(NO3)3·9H2O; Group 4: 1.103 g of C6H9O6La, 1.571 g of Mn(NO3)3·6H2O, 0.808 g of Fe(NO3)3·9H2O; Group 5: 0.945 g of C6H9O6La, 1.745 g of Mn(NO3)3·6H2O, 0.808 g of Fe(NO3)3·9H2O) and placed them into 5 beakers respectively. Then, citric acid was weighed and added into the beakers according to the molar ratio of the total metal ions to citric acid in each group being 1:1; (2) Add 25 mL of distilled water into the beaker, and adjust the pH of the solution to 7 with ammonia water; put the obtained solution into a water bath, and continuously stir it magnetically at a constant temperature of 80 °C for 4 h for gelation reaction to obtain a gel; (3) Put the gel into a blast drying oven and dry it at 180 °C for 1 h. Finally, the precursor was calcined at 900 °C for 8 h with a heating rate of 1 °C / min to obtain the perovskite wave-absorbing material.

[0027] Example 2

[0028] (1) According to the molecular formula (La 1-x Mn x )Mn 1-y Fe y Co z O3, where x = 0.3, y = 0.4, 0 < z ≤ 0.4. Weigh 1.103 g of C6H9O6La, 1.571 g of Mn(NO3)3·6H2O, and 0.808 g of Fe(NO3)3·9H2O and place them into four beakers respectively. Then, add 0.173 g, 0.345 g, 0.518 g, and 0.690 g of Co(NO3)2·9H2O into the beakers respectively. Then, weigh and add citric acid into the beakers according to the molar ratio of the total metal ions to citric acid in each group being 1:1; (2) Add 25 mL of distilled water into the beaker, and adjust the pH of the solution to 7 with ammonia water; put the obtained solution into a water bath, and continuously stir it magnetically at a constant temperature of 80 °C for 4 h for gelation reaction to obtain a gel; (3) The gel was placed in a forced air drying oven and dried at 180°C for 1 h. Finally, the precursor was heated to 900°C at a heating rate of 1°C / min and calcined for 8 h to obtain a perovskite absorbing material.

[0029] from Figure 1 As can be seen in Figure 2, the products obtained in Examples 1 and 2 have similar diffraction peaks. As x increases, the mismatch in ion size causes the XRD peak position to shift to higher angles, and a second phase, Mn2O3, is formed. As z increases, the unit cell volume increases accordingly, causing the characteristic XRD peak to shift to lower angles.

[0030] from Figure 2 It can be seen that the morphology of the material is caused by the irregular accumulation of nanoparticles, which leads to the formation of a large number of pores in the agglomerates and then the construction of a network structure, which promotes the multiple reflection and attenuation process of the absorbing material.

[0031] from Figure 3 It can be seen that with the increase of x, the Mn 4+ / Mn 3+ The ratio showed a downward trend, Fe 2+ / Fe 3+ The ratio is basically unaffected, while the oxygen vacancy concentration shows an upward trend. Due to the unique double exchange interaction of manganese ions, the polarization effect increases with the increase of Mn 4+ As z increases, the Mn content on the sample surface increases. 4+ / Mn 3+ ratio and Fe 2+ / Fe 3+ The ratio shows a trend of first decreasing and then increasing, while the oxygen vacancy concentration shows a decreasing trend. The reduction of oxygen vacancies weakens the space charge polarization. The precipitation of Fe3O4 introduces interface polarization, but it is not enough to offset the decrease in the polarization ability of the matrix. 3+ / Fe 3+ The increase in content leads to enhanced double exchange, increased electron hopping frequency and increased conductivity. 4+ The increase in content weakens double exchange and hinders electron transport. The reduction in oxygen vacancies inhibits ionic conduction. The electrical conductivity decreases, resulting in a reduction in conduction losses.

[0032] from Figure 4 As can be seen from the figure, with the increase of x, the mixed valence of manganese ions and iron ions leads to the formation of ferromagnetic and antiferromagnetic interactions, which leads to the increase of coercivity and magnetic loss, and helps to enhance the absorption characteristics of the material. 2+ The superposition of the magnetic moment contributions further strengthens the increase of the magnetic moment, thereby increasing the coercive force and magnetic loss.

[0033] from Figure 5It can be seen that the sample with x=0.3, y=0.4, z=0 has the same frequency response at 14.64 GHz and d =2.0 mm, the minimum reflection loss is -28.09 dB, and the widest effective absorption bandwidth is 6.08 GHz, showing adjustable absorption performance in the Ku band (12-18 GHz), high absorption intensity, and wide effective absorption bandwidth. The sample with x=0.3, y=0.4, z=0.2 has a maximum absorption loss of -28.09 dB at 6.48 GHz and a maximum effective absorption bandwidth of 6.08 GHz. d =4.5 mm, the minimum reflection loss is -51.44 dB, and the widest effective absorption bandwidth is 2.64 GHz, showing adjustable absorption performance in the C-band (4-8 GHz), high absorption intensity, and wide effective absorption bandwidth.

[0034] from Figure 6 It can be seen from the graph that the impedance matching of the sample of the embodiment is excellent. Figure 7 、 Figure 8 The absorbing performance data of the example samples are listed in detail, which shows that the perovskite absorbing material of the present invention can achieve adjustable absorbing performance in the C band (4-8 GHz) and Ku band (12-18 GHz), and has high absorption intensity in the C band and Ku band and a wide effective absorption bandwidth.

Claims

1. A perovskite absorbing material with adjustable wavelength, characterized in that: The absorbing material is a perovskite structure, and its chemical composition formula is (La 1-x Mn x )Mn 1-y Fe y Co z O3 absorbing material, where x, y, and z are molar coefficients, 0≤x≤0.4, y=0.4, 0≤z≤0.4; Adjustable absorption performance in the Ku band (12-18 GHz), preferably, 0≤x≤0.4, y=0.4, z=0; Adjustable absorption performance in C band (4-8 GHz), preferably, x=0.3, y=0.4, 0 <z≤0.4。 2. A method for preparing the perovskite absorbing material according to claim 1, characterized in that: The preparation method comprises the following steps: 1-x Mn x )Mn 1-y Fe y Co z C6H9O6La, Fe(NO3)3·9H2O, Mn(NO3)3·6H2O, C6H8O7 and NH3·H2O were weighed and placed in a beaker according to the values of the molar coefficients x and y of O3; Co(NO3)2·9H2O was weighed according to the value of the molar coefficient z and placed in the above beaker, and the mixture was dissolved in 25 mL of distilled water, maintaining a molar ratio of citric acid to metal ions of 1:1, and stirred for 0.5 h; the resulting solution was heated and stirred at 80 °C for 4 h to induce sol formation; the sol was then dried in an air drying oven at 180 °C for 1 h to obtain a precursor; finally, the precursor was heated to 900 °C at a heating rate of 1 °C / min and calcined for 8 h to obtain the perovskite absorber material.

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