High-performance Ferroelectric Microwave Absorption Materials

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(1.Inner Mongolia Key Laboratory of Ferroelectric-related New Energy Materials and Devices,Inner Mongolia University of Science and Technology,Baotou 014010,China;2.Department of Physics,Tangshan Normal University,Tangshan 063000,China;3.School of Material Science and Engineering,Beijing Institute of Technology,Beijing 100081,China)

ABSTRACT:Due to high polarization,excellent chemical and thermal stability,ferroelectric materials have attracted great attention of the researcher in microwave absorption field.Many works about ferroelectric microwave absorption materials were reported in the last twenty years.Here,the loss mechanisms and performances of microwave absorption of typical ferroelectric materials are summarized in detail.For the electrical loss mechanisms of ferroelectrics,dielectric loss,electric conductance loss and interface loss mechanism are summarized.For multiferroics and ferroelectric-magnetism hybrid composites,magnetic loss and magnetic-dielectric synergy mechanism are summarized.Simultaneously,the constitutive principle and action principle of the loss types are summarized.For the microwave absorption performances,the properties of BiFeO3- and BaTiO3-based materials in recent years are summarized,including single phase materials,doped materials and composite materials of them.The properties of microwave absorption at room temperature are compared with that at high temperature.Moreover,according to the relation between structure and microstructure of ferroelectric materials and absorption intensity and effective absorption bandwidth of ferroelectric materials,the microwave response mechanisms are summarized.Finally,the problems that hinder the growth of ferroelectric microwave absorption materials are analyzed,and the development outlook of the materials in the future is stated.

KEY WORDS:ferroelectric; microwave absorption; dielectric; loss; electric conductance; relaxation

1 Introduction

Microwave absorption materials with high efficiency and broadband absorption are well-suited for a variety of applications in electromagnetic irradiation shielding,signal and data protection and national defense security[1-8].In the last twenty years,various microwave absorption materials have been developed rapidly,including carbon[2,3,5,9-11],metal[6,12-20],semiconductor[21-29]and hybrid materials[1,30-38].However,it is not neglected that low loss,weak stability,complicated preparation technology and high cost are still the actual choke points for the materials.Therefore,searching for new materials with large loss,excellent stability and industrialized potential has universal significance and practical value.

As a noncentrosymmetrical structure,ferroelectrics possess higher polarity compared with other dielectric materials due to their spontaneous polarization.Moreover,the defects and interfaces in ferroelectric materials can induce polarization behavior as well.The polarizations lead to obvious dielectric response to generate dielectric loss in microwave frequency band.In addition,multiferroic materials and ferroelectric-magnetic composites possess dielectric loss and magnetic loss synchronously.The microwave electromagnetic responses promote the development of ferroelectric materials in microwave absorption field in recent years.Many ferroelectric materials have been developed.As a typical ferroelectric,BaTiO3is a potential microwave absorption material due to its dielectric relaxation.Furthermore,multiferroic materials with both dielectric loss and magnetic loss,e.g.BiFeO3and Aurivillius-type ferroelectrics,are also candidate materials in microwave absorption field.The materials exhibit excellent microwave absorption performances[39-43].Peculiarly,unexpected absorption behaviors and mechanisms are achieved in ferroelectric materials,such as thermal frequency shift,multiple absorptions,magnetic-dielectric synergy effect[8,43-45].However,low electromagnetic loss and weak electromagnetic matching of ferroelectric materials are still the bottlenecks that cause poor microwave absorption properties.How to improve the absorption properties of ferroelectric materials is a challenge.It is suggested that morphology,phase,domain and electronic structure are the dominant factors to decide the polarization and magnetism,which will affect the electromagnetic response.Therefore,clipping the structure and microstructure of ferroelectric materials is the nature way to tune microwave absorption properties,which is the main research direction of ferroelectric microwave absorption materials.

In the article,we first describe the loss mechanism from polarization,conduction and magnetism,especially the different origin of dielectric polarization based on structure and microstructure of ferroelectric materials.Then,comprehensively review the microwave absorption performances of typical ferroelectric materials.Furthermore,we discuss the outlook of ferroelectric materials,and forecasting their development in microwave absorption field in the future.

2 Loss mechanisms of ferroelectric microwave absorption materials

The nature of microwave absorption is a conversion of energy,which is achieved by the interaction between absorbers and electromagnetic wave.A strong attenuation requires that the structure of materials has an intense response for electromagnetic wave.The macroscopic behavior of the response is loss,which is achieved by polarization,electric conductance or magnetic resonance generally,and the mechanism of the loss from different origin is different.Furthermore,the matching of the loss also a crucial factor to determine the attenuation performances.For ferroelectric materials,the origin and mechanism are complicated due to their special structure.It is confusing and is a long sought-after goal of researchers in the field.

2.1 Electrical loss

Based on Debye theory,the real permittivity (ε')and imaginary permittivity (ε") follows the formula:

whereωis the angular frequency,ε∞the relative dielectric permittivity at the high frequency limit,εsthe static permittivity,andτthe relaxation time,σis the electrical conductivity,ε0is the vacuum permittivity.It is concluded that theε"consists of two contributions:polarization and electric conductance.Therefore,for most microwave absorption materials,electric loss is comprised of polarization loss and electric conductance loss.Compared with other microwave absorption materials,ferroelectric materials have various polarization modes,including orientation polarization related to the noncentrosymmetric nature of the ferroelectric unit cell,defect polarization induced by defect dipoles and interface polarization caused by domain boundary,grain boundary or heterogeneous interfaces.When ferroelectric materials are in electromagnetic field,the polarization vectors will rotate following the direction of electromagnetic wave.With the increase of the frequency,the rotate of the polarization vectors do not follow the change of the frequency,leading to the polarization loss.The dielectric loss induced by orientation polarization is observed at many ferroelectric materials.Liet alfound that pure BiFeO3possessed obvious dielectric relaxation in theε",which is induced by orientation polarization from the lone pair of Bi ion[8,44-47],as shown in Fig.1a.Moreover,the dielectric relaxation do not disappear in doped BiFeO3and BiFeO3-based composite materials,indicating that the orientation polarization a intrinsic origin of loss[8,44-46,48].Wanget alinvestigated the microwave electromagnetic properties of (1-x)Co2Z-xBaTiO3composites.It is suggested that the permittivity spectra of the composites in gigahertz ranges are mainly associated with orientation polarization and interfacial polarization,indicating that the orientation polarization is an important factor to cause dielectric loss for BaTiO3-based ferroelectric materials[49],as shown in Fig.1b.

The defect polarization is another key factor to induce dielectric loss.Inorganic ferroelectric materials can generate point defects in crystal lattices due to nonstoichiometry of component,e.g.cation vacancy and oxygen vacancy.The defects can form defect dipoles which induce defect polarization.Peculiarly,oxygen vacancy is a crucial origin of defect polarization in ferroelectrics.Yuanet aldemonstrated that high dielectric constant and dielectric loss of BiFeO3in the Ku band were primarily dominated by defect relaxation induced by oxygen vacancies based on the relation relaxation time and temperature[50].Liet alfound that pure BiFeO3possessed two relaxation peaks in theε"in 8.2～12.4 GHz.However,La,Nb doped BiFeO3just had a dielectric relaxation in the frequency range due to the decrease of oxygen vacancies[8,44,46],as shown in Fig.2a—b.The result verifies that defect polarization from oxygen vacancies exists in BiFeO3.Baeket alreported that BaTiO3-based composites exhibited a 35%enhancement in dielectric loss due to the increase of oxygen vacancy concentration in BaTiO3.Sunet alalso demonstrated the broad relaxation peak of theε"at 5～12 GHz is caused by the intrinsic and defect dipoles in Aurivillius Bi7Fe2.1Co0.9Ti3O21ferroelectric material[43],as shown in Fig.2c—e.The research results indicate that defect polarization plays an important part in dielectric loss of ferroelectric materials.

In addition,the interface polarization also can be formed as an origin of dielectric loss in ferroelectric materials.When two materials or two phase in one material,which have different polarity and conductivity,come into contact with each other,the positive and negative charges can be generated on both sides of the interfaces,leading to the interface polarization.Gaoet alprepared 3D porous BiFeO3/RGO composite which possessed largerε'andε"than porous BiFeO3at 2～18 GHz.It is suggested that interface polarization formed between porous BiFeO3and RGO acts as polarization centers,resulting in the enhancement of dielectric loss[51],as shown in Fig.3a—b.Liet alfound that the positive-negative charge pairs in the interface of BiFeO3/BaFe7(MnTi)2.5O19with heterogeneous double layer structure induced a strong interface polarization,leading to a big dielectric relaxation.Thus compared with pure BiFeO3and BiFeO3/BaFe7(MnTi)2.5O19with homogeneous structure,double layer BiFeO3/BaFe7(MnTi)2.5O19possesses larger dielectric loss[48],as shown in Fig.3c—d.Other ferroelectric composites,e.g.Fe3O4-BaTiO3composites and Ni0.4Co0.2Zn0.4Fe2O4/BaTiO3composite fibers also exhibit obvious interface polarization which induce dielectric loss[52-53],as shown in Fig.3e—j.

Due to conductance of materials,the microwave absorption materials more or less possess electric conductance loss in electromagnetic field,which is closely related to the magnitude of conductivity.For instance,carbon and metal with high conductivity cause strong electric conductance loss,which is the main electromagnetic attenuation mechanism of the materials[2,10,18].Generally,most of ferroelectric materials have large bandgap (＞ 2.5 eV),exhibiting insulativity.Therefore,the contribution of electric conductance loss for electromagnetic attenuation is tiny at low temperature.Yuanet alsuggested that the high dielectric loss of BiFeO3should be primarily dominated by defect relaxation loss rather than leakage conductance loss through the research on the electric conductance and dielectric loss behavior[50].It is found that DC conductance of BiFeO3is poorly temperature-dependent below 600 K.Moreover,Liet alinvestigated the electric conductance loss mechanism of doped BiFeO3in depth[8,44,46].According to Debye theory,theε"is comprised of the conduction part (εc") and the polarization part (εp").It is also found that theεc"has a tiny proportion of theε"in BiFeO3from 323 K to 673 K.Differently,for La,Nb doped BiFeO3,although theεp"primarily contributes to theε",theεc"plays important role above 473 K,due to the change of electric conductance mechanism after doping,as shown in Fig.4.Therefore,electric conductance loss is related to structure of materials and temperature.

2.2 Magnetic loss

Part of ferroelectrics possess ferromagnetism,which are termed multiferroic materials,e.g.BiFeO3,ReMnO3(Re = rare earth element),ReMn2O5,PbFe1/2Nb1/2O3.Therefore,they exhibit dielectric loss and magnetic loss in electromagnetic field simultaneously.In the microwave frequency band,the mechanism of magnetic loss includes natural resonance,domain wall resonance,exchange resonance,and micro eddy current loss,etc.[4,54].Houet alfound that the magnetic loss of BiFeO3was caused by natural ferromagnetic resonance rather than micro eddy current,and ions doping can improve the ferromagnetic properties of BiFeO3due to destruction of spin cycloid structure,leading to the enhancement of magnetic loss[54-55],as shown in Fig.5a—c.Liet alfound that rare earth doping can enhance exchange interaction of BiFeO3,leading to the increase of natural ferromagnetic resonance which is the dominated magnetic loss mechanism[8],as shown in Fig.5d—f.In addition,ferroelectric materials with special morphology and ferroelectric composites can exhibit multiple resonance behavior.In flower-like porous Bi0.9La0.1FeO3microspheres,the eddy current loss,exchange resonance and nature resonance work together to induce the magnetic loss[56].The magnetic loss of BiFeO3-paraffin wax composites is caused by domain resonance,natural resonance and exchange resonance[45].

2.3 Magnetic-dielectric synergy

For microwave absorption materials,high dielectric loss and magnetic loss are the basics to achieve strong absorption.However,if dielectric loss and magnetic loss are only lack of balance,the microwave absorption won’t reach a high value.Therefore,the matching level of electromagnetic loss is also a significant factor to determine the microwave absorption performances.Caoet alestablished the theory in 2003,which demonstrates that the electromagnetic parameters of absorber correspond to the matching case when tanδeis be equal to tanδm[5].Some experimental results of multiferroic materials verify the theory further.Sunet alfound that a relative balance between the tanδmand the tanδein Aurivillius-type multiferroic oxides at 13～18 GHz leaded to high-performance microwave absorption[43].Liet alprobed the relation between electromagnetic loss matching and microwave absorption through Nd doped BiFeO3.With the increase of Nd concentration,the tanδedecreases moderately and the tanδmincreases,leading to the development of electromagnetic parameters from mismatching to matching,thus the microwave absorption properties are enhanced[8],as shown in Fig.6a.Other multiferroic materials also show the similar behavior based on the mechanism[45,47,55,57],as shown in Fig.6b—c.Therefore,for multiferroic and ferroelectric-magnetism composites,electromagnetic loss matching can be not neglected,which is a theoretical direction for the designing of microwave absorption materials.

3 Microwave absorption of ferroelectric materials

Generally,microwave absorption performances are evaluated by the intensity of reflection loss (RL) and effective absorption bandwidth (RL＜-10 dB).The RL is calculated according to transmission line theory.When the frequency and thickness of absorber are known,the RL is calculated as:

Here the normalized input impedanceZinof the microwave absorption layer is calculated based on the formula:

wherecis the light velocity,fis the electromagnetic wave frequency,dis the thickness of the absorber,εris the complex permittivity,andμristhe complex permeability.Based on the formulas,it is found that tuning the electromagnetic parameters is the intrinsic way to improve the microwave absorption performances.

3.1 Microwave absorption of BiFeO3-based materials

BiFeO3is a multiferroic material that is both magnetic and a strong ferroelectric at room temperature,leading to its multifunctional development in ferroelectric,piezoelectric,energy storage,photovoltaic and photocatalysis fields.Furthermore,both dielectric loss and magnetic loss of it open new perspectives as a high-performance microwave absorption material.In 2009,Kanget alreported the microwave absorption properties of BiFeO3nanoparticles for the first time[39].The optimal RL reaches to -26 dB,and the effective absorption bandwidth approaches 4 GHz in the Ku band,as shown in Fig.7a—c.Such results attracted great attention for researchers.Subsequently,BiFeO3nanoparticles and ceramics as the microwave absorption materials were studied widely.Wenet alprepared high denser BiFeO3ceramic by high-pressure synthesis method[58].The method increases crystal structure deformation and crystallization of BiFeO3ceramic,leading to the enhancement of magnetic loss and dielectric loss.The optimal RL of BiFeO3ceramic in 2～18 GHz is elevated from -13 dB to -17 dB,as shown in Fig.7d—f.Sowmyaet alsynthesized pure and well-crystallized BiFeO3nano-crystallites by optimized sol-gel method,and investigated the microwave absorption performance in the Ku band[59].The RL is -46 dB for 2 mm thick sample,and the attenuation peak also shifts to a lower frequency when the thickness increases.Moreover,Yuanet alprobed the microwave absorption performance of BiFeO3in the temperature range of 373～773 K in the Ku band[50].BiFeO3shows high dielectric loss and a strong positive temperature dependence of dielectric properties,as shown in Fig.8a.However,a monotonic decrease for the RL is observed when the temperature increases,as shown in Fig.8b.In addition,it is found that the absorption peaks are in the neighboring positions ofdn/λ=1/4 (wheredis the thickness of the absorber,λis the wavelength in a vacuum,andnis the refractive index of materials),indicating that the reflection loss refers to the contribution of quarterwavelength attenuation.

However,the microwave absorption properties of BiFeO3are still limited by the electromagnetic mismatching.Therefore,many works on how to tune electromagnetic properties of BiFeO3were carried out.Ions doping as a simple and effective way was widely applied to enhance the microwave absorption properties in BiFeO3[8,41,44,46,54-56,60-62].Andryushinet alinvestigated systematically the effect of rare earth (Re=Lu,Yb,Tu,Er,Ho,Dy,Tb,Gd,Eu,Sm,Nd,Pr,La) on relaxation dynamics and microwave absorption properties of BiFeO3[60].It is found that the change of rare earth ion radius is accompanied by a wave like variation of the dielectric properties,with sequential maxima and minima in bothε'and tanδ,as shown in Fig.9.The effects are related to the appearance of symmetry phase transitions,specific features of the crystal chemistry of rare earth elements,and changes in the type of solid solutions.Moreover,ions doping can change the crystal structure,defect structure and electron structure of BiFeO3,leading to the enhancement of microwave absorption properties.Liet alfound that Nd doping generated the ordered structure and changed the coupling states of electrons,which induce difficult polarization rotation and strong natural ferromagnetic resonance,leading to the electromagnetic matching,as shown in Fig.10a.Bi0.8Nd0.2FeO3(BNFO20) exhibits a remarkable RL of -42 dB and effective absorption bandwidth which covers nearly three quarters of the X-band[8],as shown in Fig.10b.Houet alutilized interfacial engineering in BiFeO3nanoparticles via Ca doping to broaden the effective absorption bandwidth[55].Upon Ca-substitution,the co-existence of bothR3candP4mmphases has been confirmed to enhance both dielectric and magnetic properties via manipulating the phase boundary and the destruction of the spiral spin structure,as shown in Fig.10c—e.In addition,the microwave absorption properties of doped BiFeO3in temperature field were studied.Biet alreported the electromagnetic properties and microwave absorption performance of Bi1-xMgxFeO3in the temperature range of 323～723 K in X-band[61].It is observed that the RL and bandwidth of Bi1-xMgxFeO3exhibit temperature dependence.The RL increases firstly and then decreases,and the effective absorption bandwidth of Bi0.95Mg0.5FeO3covers the whole X-band at 673 K.Interestingly,Liet alreported the original observation of thermal frequency shift of dielectric relaxation in La/Nd doped BiFeO3in X-band from 300 to 673 K[44].An unexpected result is exhibited: the relaxation peak shifts to lower frequency with increasing temperature,as shown in Fig.11a—c.The frequency shift achieves tunable microwave absorption,of which absorption peak can be shifted 3.2 GHz by changing temperature,as shown in Fig.11d—f.It is suggested that the nonlinear term of lattice vibration plays an important role in the frequency shift.

In addition,to improve the microwave absorption properties of BiFeO3,magnetic materials,carbon materials and organic materials are combined with BiFeO3to form various composites[47,51,57,63-65].The purpose of the design is to enhance conductivity and magnetism and form interface polarizations,resulting in the increase of electromagnetic loss and the improvement of electromagnetic matching.Moitraet alinvestigated the microwave absorption properties of BiFeO3nanowire-RGO nanocomposite.It is found that the adding of 3wt% RGO increases the RL from -6.7 dB to -28.68 dB due to the increase of dielectric loss.The conductivity loss and combined loss of the dipole polarization and interfacial polarizations are two important factors which contribute to the electric loss[65],as shown in Fig.12a—c.Analogously,Gaoet alsynthesize flowerlike BiFeO3microspheres/graphene composite.Compared with BiFeO3,the composite exhibit excellent microwave absorption properties,achieving RL of -46.7 dB and effective absorption bandwidth of 4.7 GHz,due to the multiple polarizations including interfacial polarization and dipole polarization[51].The results indicate that the enhanced mechanism of microwave absorption for BiFeO3-carbon composites is the increased contribution of dielectric loss.However,the adding of carbon usually has a weak effect on magnetism.It is also desired for BiFeO3to enhanced microwave attenuation by compositing with strong magnetic materials.Cao and his group further highlighted the strategy[47,57].M-type hexagonal ferrite BaFe7(MnTi)2.5O19was utilized to enhance the magnetic properties of BiFeO3and improve electromagnetic matching.BiFeO3- BaFe7(MnTi)2.5O19composites exhibit multi-relaxation behavior and enhanced magnetic loss,and electromagnetic matching can be achieved at a suitable proportion of BiFeO3,leading to the RL of -50 dB,as shown in Fig.12d—f.In addition,organic materials,e.g.polyaniline (PANI),acrylo-nitrile butadiene rubber (NBR),also were used to composite with BiFeO3[63-64].The results exhibit that the BiFeO3-organic composites have enhanced microwave absorption properties (RL＜-40 dB) and dual band resonating microwave absorption behavior,as shown in Fig.12g—i.

3.2 Microwave absorption of BaTiO3-based materials

BaTiO3as a classical ferroelectric has been attracting attention in the fields of capacitor,thermistor,electro-optical devices.Due to marked dielectric relaxation in the dielectric properties,BaTiO3was also used as a microwave absorption material recent years[7,40,42,49,52,53,66-68].Yanget alsynthesized ultrathin BaTiO3nanowires with high aspect ratio,which has an optimal RL of -24.6 dB and an effective absorption bandwidth of 2.4 GHz,indicating that the material is a promising microwave absorber[7].Baeket altuned the microwave absorption properties of micron-sized Ba-TiO3particles through the incorporation of axial oxygen vacancies while controlling for differences in particle size,grain size and crystalline phase[42].The increase of oxygen vacancy concentration promotes the improvement of optimal RL from -16.9 dB to -43.2 dB,due to a 35% enhancement in dielectric loss,as shown in Fig.13.In addition,doped BaTiO3materials,e.g.Srdoped BaTiO3nanocrystalline[66],also possess obvious dielectric relaxation in microwave frequency band,leading to tunable microwave absorption by changing the proportion of doped elements.

Due to lack of magnetism,BaTiO3is usually combined with magnetic materials for achieving magnetic loss.Maet alinvestigated the microwave absorption of BaTiO3-based ferroelectric/ferromagnetic nanocomposite.Compared with Ni-Co-P/BaTiO3,carbonyl iron/BaTiO3composite has larger RL and effective absorption bandwidth which reach -46 dB and 16 GHz,respectively[40],as shown in Fig.14a—b.Jiet alprepared cobalt ferrite sphere-coated buckhorn-like barium Ba-TiO3.After combination with cobalt ferrite,the RL of the composite reaches -42.677 dB.Wanget alreported the enhanced microwave absorption of multiferroic Co2Z hexaferrite-BaTiO3composites[49].For the optimal Co2Z-10BaTiO3composite,the RL at a thickness of 2.0 mm exceeds -40 dB due to impedance matching.The impedance matching characteristic between the absorber and the air is determined by the impedance matching coefficientZm,which is expressed as

where Re[x]is the real part of thex.Xianget alacquired the RL of -65.6 dB and a broad effective absorption bandwidth of 7.8 GHz in Ni0.4Co0.2Zn0.4Fe2O4/BaTiO3composite fibers.The enhanced microwave absorption arises from the synergistic effect between magnetic and dielectric components within the quasione-dimensional space,the improved interfacial effect as well as the proper electromagnetic impedance matching[53].Huanget alinvestigated the microwave absorption of Fe3O4-BaTiO3composites in the frequency range of 1～18 GHz.Compared with BaTiO3,the composites present significantly enhanced microwave absorption properties,where the optimal RL reaches-47.4 dB and the effective absorption bandwidth exceeds 5 GHz due to better impedance matching through the adding of Fe3O4[52],as shown in Fig.14c—d.In addition,organic materials are also combined with Ba-TiO3to enhance the microwave absorption properties.For instance,Sainiet alsynthesized BaTiO3/acrylonitrile butadiene rubber composites,which exhibit peculiar dual band resonance from ferroelectric-induced dipolar relaxation and second-order resonance[68],as shown in Fig.14e—f.

3.3 Microwave absorption of other ferroelectric materials

Other ferroelectric materials were also developed as microwave absorption materials.For instance,Aurivillius-type multiferroic oxide Bi7Fe2.25Co0.75Ti3O21ceramic was investigated in the microwave frequency band by Sun[43].The material exhibits excellent microwave absorption properties.The maximum RL of all samples with different thickness surpasses -30 dB.Especially,the optimal RL reaches -70.1 dB at the thickness of 2 mm and the absorption bandwidth (RL＜-20 dB) is close to 12 GHz.Mitraet alreported the microwave absorption properties of LaFeO3and LaFeO3-multi-walled carbon nanotubes composites in X and Ku bands[69].The composites possess the optimal RL of-34.88 dB at the thickness of 1 mm.Moreover,organic ferroelectric polyvinylidene fluoride (PVDF) and P(VDF-TrFE) are used in the microwave absorbers as a polar matrix[70-71].For instance,Wanget alinvestigated the electromagnetic and microwave absorption properties of polymer-based Ba3Co2Fe24O41/P(VDF-TrFE)composites,of which the maximum RL exceeds-35 dB[71].

4 Summary and outlook for development of ferroelectric microwave absorption materials

Based on the above overview,it is concluded that ferroelectric materials are promising microwave absorption materials due to their multiple polarization,magnetic resonance and the synergistic effect of dielectric loss and magnetic loss.However,it is not neglected that ferroelectric materials that are researched in microwave absorption filed are only a few.Searching for new ferroelectrics with high loss is an important mission for the development of ferroelectric microwave absorption materials.The microwave absorption behaviors of ferroelectric materials are not mastered completely.It is essential to probe the microwave absorption properties in different thickness of absorbers,frequency and temperature.Particularly,the effect of temperature on microwave absorption properties may be a research focus for the application in dynamic environment.Moreover,the microwave response mechanism of ferroelectric materials needs to be discussed and analyzed deeply,including dielectric relaxation,ferromagnetic resonance and the magneto-electric synergistic,etc.Based on the results and mechanism,establishing the tuning way of microwave absorption and design strategy of material structure is a major direction in ferroelectric microwave absorption materials in the future.