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ChemPhysMater xxx (xxxx) xxx
Contents lists available at ScienceDirect
ChemPhysMater
journal homepage: https://www.keaipublishing.com/en/journals/chemphysmater/
Recent progress of electromagnetic wave absorbers: A systematic review
and bibliometric approach
Yuksel Akinaya,∗
, Umit Gunesb
, Bektaş Çolakc
, Tayfun Cetind
a
Mining Engineering, Van Yuzuncu Yil University, Van 65080, Turkey
b
Naval Architecture and Marine Engineering, Yildiz Technical University, Besiktas, Istanbul 34349, Turkey
c
Natural Sciences Faculty, Physics Department, Gebze Technical University, Gebz 41400, Turkey
d
Yuksekova Vocational High School, Hakkari University, Hakkari 30110, Turkey
a r t i c l e i n f o
Keywords:
Electromagnetic wave absorption
Microwave absorption
Bibliometric approach
Reflection loss
Composites
a b s t r a c t
The electromagnetic wave absorption capabilities of an absorber depend on its dielectric and magnetic compo-
nents, which determine its interfacial polarization, conductivity loss, magnetic loss, and other such mechanisms.
In this study, a comprehensive review of the electromagnetic wave and material interaction was conducted.
Moreover, for a better understanding of the trends and evolutionary developments in the study of the electro-
magnetic wave absorber, 23300 documents dated between 1990 and 2020 were examined, which were obtained
from Scopus using the keywords of “electromagnetic wave absorption” and “microwave absorption”. The data
search in Scopus was conducted using the related keywords in the search bar for titles and abstracts. These results
demonstrate that the majority of research regarding electromagnetic wave absorbers was conducted in China,
which was followed by the United States. The number of published documents regarding the electromagnetic
wave absorption field significantly increased between 1990 and 2020; these documents were mostly published
as journal articles. With respect to the journal activity, the most productive journal was the “Journal of Alloys
and Compounds”, with a total of 592 articles. In addition, graphene and titanium dioxide were determined to be
the materials that were most studied in the field of electromagnetic wave absorption.
1. Introduction
The rapid development and increased use of electronic devices have
led to significant electromagnetic wave pollution. However, the ability
to detect aircrafts using electromagnetic waves is an important prob-
lem in stealth technology. Therefore, electromagnetic wave absorbers
(EMAs) have become one of the most studied materials in the last decade
[1–3]. Electromagnetic wave absorbers are expected to have properties
such as a high electromagnetic wave attenuation, are light weight, have
a thin coating thickness, and a broad absorption bandwidth in the gi-
gahertz frequencies. EMAs reduce the radar cross-section (RCS), which
is the detection ability of a target by electromagnetic waves. To reduce
RCS, different types of electromagnetic wave absorbers have been de-
veloped. EMAs can be divided into the following two groups with re-
spect to the loss type: magnetic and dielectric loss materials [4–7]. The
ability of a material to absorb electromagnetic waves involves the mea-
surement of the reflection loss, which is represented in decibels; more
negative values of the reflection loss provide a higher incident wave
attenuation performance. For example, a reflection loss of −10 dB re-
duces the electromagnetic wave power by approximately 90%, while
∗
Corresponding arthor.
E-mail address: yukselakinay@gmail.com (Y. Akinay).
a reflection loss of −20 dB reduces the wave power by approximately
99% [8,9]. The microwave characterization of EMAs involves the fol-
lowing two main types of measurements: free space and guided space.
Free space techniques are most useful for end-users and fast checks dur-
ing the quality control of the mass production cycle [1,2] and require
relatively large sample sizes. Unfortunately, this requirement was un-
able to be satisfied at the early stage of EMA research because most
of the studies in this field started with small sample sizes. However,
guided techniques require small sample sizes and are sensitive to vari-
ations in the sample orientation and size. The main test equipment for
both techniques is a vector network analyzer operating in the related fre-
quency band. Two wide-band horn antennas were used for free-space
techniques. The guided techniques use waveguides in the related fre-
quency bands. The S parameters were measured, including the reflec-
tion and transmission coefficients from the sample under measurement.
Depending on the measurement technique used, a perfect metal con-
ductor plate is occasionally placed behind the sample. The electromag-
netic medium parameters, such as the complex dielectric permittivity
ɛ and the complex magnetic permeability 𝜇, were calculated from the
measured S parameters of the sample under measurement. Using these
https://doi.org/10.1016/j.chphma.2022.10.002
Received 15 August 2022; Received in revised form 24 October 2022; Accepted 24 October 2022
Available online xxx
2772-5715/© 2022 The Authors. Publishing Services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC
BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Please cite this article as: Y. Akinay, U. Gunes, B. Çolak et al., Recent progress of electromagnetic wave absorbers: A systematic review and
bibliometric approach, ChemPhysMater, https://doi.org/10.1016/j.chphma.2022.10.002

Y. Akinay, U. Gunes, B. Çolak et al. ChemPhysMater xxx (xxxx) xxx
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Fig. 1. The measurement geometry with PEC plate termination under the sam-
ple.
calculated electromagnetic medium parameters, the reflection loss for
any thickness of the sample can be calculated. The measurement ge-
ometry with the PEC plate termination under the sample is shown in
Fig. 1.
The final reflection coefficient RL is related to the S11 parameter
measured at the z=0 point, as is the front surface of the sample where
it faces free space (Z1=Z0=377 Ω), and is given as follows:
𝑅𝐿(dB) = 20log
[
Γ12
]
. (1)
The S11 parameter is related to the imbalance of the impedances at
the front surface of the sample.
𝑆11 =
𝑍2(in) − 𝑍1
𝑍2(in) + 𝑍1
. (2)
The term Z2(in) also includes the transferred imperfections at the back
surface of the sample with the PEC plate:
𝑍2(in) = 𝑍2
𝑍3 + 𝑍2 tanh 𝛾2𝑧′
𝑍2 + 𝑍3 tanh 𝛾2𝑧′
, (3)
where z’ = d, and Z3 = 0 Ω. The electromagnetic medium parameters of
the sample were included in the calculations over Z2, which reflects the
impedance of the sample itself.
𝑍2 =
√
𝜇0
𝜀0
√
𝜇𝑟2
𝜀𝑟2
. (4)
Here, the sample parameters are given as follows:
𝜀𝑟2 =
𝜀′ − 𝑖𝜀′′
𝜀0
, 𝜇𝑟2 =
𝜇′ − 𝑖𝜇′′
𝜇0
. (5)
Furthermore, the propagation constant 𝛾 is defined as follows:
𝛾 = 𝑗𝑘0𝑘𝑟2, (6)
where
𝑘0 =
2π𝑓
𝑐
, 𝑘𝑟2 =
√
𝜇𝑟2𝜀𝑟2. (7)
Recently, several dielectric and magnetic components have been syn-
thesized for the desired electromagnetic wave absorption performance
at the micro- and nano- thickness levels. Carbon, graphene, carbon nan-
otubes, perovskite ferroelectrics, and conductive polymers are the most
studied dielectric components, with iron, nickel, ferrites, and magnetic
metal oxides being the components used as magnetic fillers [10–15].
A high electromagnetic wave absorption performance is generally un-
achievable using a single type of component, such as a dielectric or
magnetic filler, owing to it provide only a single type of loss. Hence,
combining both dielectrics and magnetic fillers provides a high absorp-
tion performance owing to good impedance matching and strong in-
terfacial polarization [16]. Recently, the combination of dielectric and
magnetic materials as novel structural materials has been intensively
studied with regard to EM wave absorbers. Wu et al. [17] synthesized hi-
erarchical porous Cobalt/Carbon (Co/C) crabapples by combining mag-
netic and dielectric components. A minimum reflection loss of −56.9
dB at 9.3 GHz was obtained with a 1.92 mm thicknesses owing to the
strong magnetism of Co and the porous structure of the material. One
of the most promising materials in electromagnetic wave absorbers are
metal-organic frameworks owing to their large surface area. Yan et al.
[18] prepared a new type of nickel-based (Ni) metal-organic frame-
work demonstrating a strong absorption ability. Liu et al. [19] prepared
nanocomposites of reduced graphene oxide with silica-coated magnetite
(Fe3O4@SiO2) nanoparticles using a modified version of the Hummers’
method. They reported a minimum reflection loss of −55.4 dB obtained
with a 1:1 weight ratio of graphene to Fe3O4@SiO2 at a thickness of
3.5 mm. Recent studies have focused intensely on EM wave absorbers.
However, no extensive data reports have been found regarding the un-
derstanding of the trend of activities of the EM wave absorbers or their
evolutionary road map from the past to the present. Bibliometric anal-
ysis is the statistical data analysis of documents published in a related
field based on appropriate keywords to reveal research activity. This
statistical approach identifies research activities and leading research
groups by using scientific databases in a particular field [20]. Thus, this
study aims to report a bibliometric analysis of the electromagnetic wave
absorbers by identifying the comprehensive research trends from 1990
to 2020. A general prospective for the current study is provided consid-
ering the following steps: (1) a timeline of the annual published docu-
ments and citations, (2) journal analyses (i.e., most productive journals
and their subject areas), (3) most productive countries and regions, and
(4) keyword and keyword cluster analyses. To the best of our knowledge,
this is the first study regarding a bibliometric analysis of the electromag-
netic wave absorbers.
2. Electromagnetic wave absorption mechanisms
When an incoming electromagnetic wave interacts with a material,
it is attenuated or reflected back through the following three different
mechanisms: reflection, absorption and transmission at the molecular
level. In an ideal absorber material, the power of the incident electro-
magnetic wave is expected to be converted into heat energy, resulting
in less reflection and a higher absorption [21]. Fig. 2 demonstrates the
different behaviors of the electromagnetic wave and material interac-
tions. The electromagnetic wave absorption performance of the absorber
material was estimated using the reflection loss value in decibels. The
reflection loss value is measured by the dielectric and magnetic com-
ponents of the materials, and more negative reflection values provide a
better absorption performance. In general, dielectric materials exhibit
conductance and polarization losses (ionic, dipole, and interfacial po-
larization).
According to the free electron theory (𝜀′′ = 𝜎
2π𝑓𝜀𝑛
), the imaginary
part of the permittivity (𝜀′′) increases with an increasing conductivity
(𝜎). In this theory, the conductance loss plays a key role in the dielectric
loss mechanism. In a heterostructure system or multiple components,
the differences between the conductivity and permittivity lead to an in-
terfacial polarization effect around their interfaces. This phenomenon
was first explained by Maxwell and Sillars as Maxwell-Wagner-Sillars
(MWS) [22].
If the absorber material also has a magnetic component, the mag-
netic loss effect also plays an important role in the electromagnetic
wave attenuation performance. Magnetic loss is due to the eddy cur-
rent effect and resonance mechanisms (exchange resonance and natural
resonance). The eddy current loss (𝐶0) is represented as follows:
𝐶0 = 𝜇′′
(𝜇′
)
−2
𝑓−1
. (8)
The resonance mechanism can be explained as the exchange reso-
nance and natural resonance, where the possible natural resonance ap-
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Fig. 2. Materials and electromagnetic wave interaction: schematic representation of the electromagnetic wave absorption and reflection.
pears at a low frequency and the exchange resonance occurs at a high
frequency.
Depending on the energy-component law, the absorption mechanism
is formulated as follows [23]:
𝑊𝑖 = 𝑊𝑡 + 𝑊𝑎 + 𝑊𝑟, (9)
𝑊𝑟 = 𝑊𝑓 = 𝑊 ∗
𝑓 , (10)
where 𝑊𝑖, 𝑊𝑡, 𝑊𝑎, and 𝑊𝑟 are the incident electromagnetic wave
energy, transmitted electromagnetic wave energy, absorbed wave en-
ergy, and total reflected wave energy, respectively. In Eq. (9), 𝑊𝑓
represents the reflected wave energy from the surface, whereas 𝑊 ∗
𝑓
indicates the electromagnetic wave energy propagation through the
absorber.
3. Methodology
The most important aspect of the bibliometric analyses is to obtain
highly accurate, classified, and standardized data. The most important
and useful platforms that present this to researchers are the Web of Sci-
ence (WoS) and Scopus. In this study, Scopus data was preferred not
only because it contains more comprehensive results than WoS, but also
because it offers keywords for publications in excess of the informa-
tion WoS presents [24]. Scopus is widely used as a high-quality bib-
liometric data source in quantitative academic studies. The analyses in
Scopus were performed according to the following steps: At the begin-
ning of the research, keywords representing electromagnetic wave ab-
sorbers were searched by performing a literature scan. Two keywords
(“microwave absorption” and “electromagnetic wave absorption”) rep-
resenting this matter were detected in the search results, which were
found in 23300 records, where either of these two words had occurred
in either the title or keywords as of December 14, 2020. The obtained
results were analyzed using separate figures. The sum of the values in
certain analyses exceeded 100%. This was because the relevant arti-
cles were evaluated separately for more than one feature. For exam-
ple, an article related to the two fields was included in the analyses in
both fields. As a result of the different keywords used in each article,
they were similarly evaluated at separate times in the relevant keyword
analyses.
Fig. 3. Timeline of published documents and citations from 1990 to 2020.
4. Data analysis and discussion
4.1. Number of published documents and citations
The annual number of scientific publications (articles, patents, con-
ference papers, and book chapters) regarding electromagnetic wave ab-
sorbers that were obtained from the Scopus Indexed Journals List (up-
dated 2020) and were published between 1990 and 2020 are presented
in Fig. 3. A total of 23300 publications were found on the Scopus In-
dexed Journals List as well as the conference proceedings. The number
of annual publications can be determined to slightly vary between 1990
and 1994, with a total of 435 being published over this period. A signif-
icant increase was observed after 1994. A total of 5650 documents were
published between 1995 and 2010, which increased to 16880 between
2011 and 2020. A rapid increase was observed between 2010 and 2017,
which may be attributed to the development of dielectric and magnetic
nanofillers, and the growing interest of EM wave absorbers (EMAs) for
stealth technology [25,26]. However, a sharp decrease in the total num-
ber of annual publications was observed between 2017 and 2020. A
decreasing trend in studies regarding electromagnetic wave absorption
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Fig. 4. Top 30 most productive journals from 1990 to 2020.
can be concluded to occur after 2017. Similarly, a rapid increase in the
total citations was observed since 2010. Considering the sharp increase
in the total publications after 2010, the increase in the total citations
was expected for these periods.
4.2. Journals and subject categories
Fig. 4 demonstrates the total number of publications in the most pro-
ductive 30 journals with more than 100 documents in the field of EM
wave absorption. The Journal of Alloys and Compounds stands out with
a total of 592 papers, followed by The International Society for Optical
Engineering (SPIE), which published a total of 582 conference papers.
RSC Advances is the third most productive journal with a total of 510
papers, followed by the Journal of Materials Science: Materials in Elec-
tronics with a total of 445 papers. The list of publications, publishers,
subject categories, and quartile ranks for the top 20 journals are pro-
vided in Table 1. All the journals have Q1 quartile ranks on the Journal
Citation Reports, with the exception of the Proceedings of SPIE (Q3),
Journal of Materials Science: Materials in Electronics (Q2), and Journal
of Physics: Conference Series (Q4).
4.3. Published document types and sub-research areas
The types of published documents are shown in Fig. 5, among which
articles constitute the majority (80.4%) between 1990 and 2020, with
a total of 18863 publications. Conference papers were the second most
prevalent (17.6%). According to this data analysis, articles and confer-
ence papers are the most frequently published types of scientific docu-
ments regarding electromagnetic wave absorption, followed by review
articles with 278 publications.
The number of documents published considering the research area
is a set of important data to be evaluated using the bibliometric ap-
proach. The distribution of scientific documents according to the sub-
research area from 1990 to 2020 is presented in Fig. 6. Among the 13
selected sub-research areas, materials science, physics and astronomy,
Fig. 5. Types of published documents.
engineering, and chemistry are the four basic areas in which electromag-
netic wave absorption publications are found at rates of 24.2%, 24.1%,
19.9%, and 12.5%, respectively. These results demonstrate that studies
regarding electromagnetic wave absorption have gained prominence as
an experimental discipline [27,28]. However, the remaining research
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Table 1
Most productive journals, their publisher, subject categories, and quartile rank
Source title
Journal’s number
of publications Publisher Subject categories Quartile
Journal of Alloys and
Compounds
592 Elsevier Engineering: Mechanical Engineering
Engineering: Mechanics of Materials
Materials Science: Materials Chemistry
Materials Science: Metals and Alloys
Q1
Proceedings of SPIE: The
International Society for
Optical Engineering
582 - Mathematics: Applied Mathematics
Engineering: Electrical and Electronic Engineering
Computer Science: Computer Science Applications
Physics and Astronomy: Condensed Matter Physics
Materials Science: Electronic, Optical and Magnetic Materials
Q3
RSC Advances 510 Royal Society of
Chemistry
Chemical Engineering: General Chemical Engineering
Chemistry: General Chemistry
Q1
Journal of Materials
Science: Materials in
Electronics
445 Springer Nature Engineering: Electrical and Electronic Engineering
Physics and Astronomy: Atomic and Molecular Physics, and
Optics
Q2
The Journal of Physical
Chemistry C
328 American Chemical
Society
Materials Science: Surfaces, Coatings and Films
Energy: General Energy
Chemistry: Physical and Theoretical Chemistry
Q1
ACS Applied Materials and
Interfaces
316 American Chemical
Society
Materials Science: General Materials Science Q1
Ceramics International 296 Elsevier Materials Science: Materials Chemistry
Materials Science: Surfaces, Coatings and Films
Materials Science: Ceramics and Composites
Chemical Engineering: Process Chemistry and Technology
Q1
Journal of Magnetism and
Magnetic Materials
287 Elsevier Physics and Astronomy: Condensed Matter Physics
Q1
Journal of Applied Physics 272 American Institute of
Physics
Physics and Astronomy: General Physics and Astronomy Q1
Applied Physics Letters 251 American Institute of
Physics
Physics and Astronomy: Physics and Astronomy
(miscellaneous)
Q1
Materials Letters 215 Elsevier Engineering: Mechanical Engineering
Engineering: Mechanics of Materials
Materials Science: General Materials Science
Q1
Journal of Physics:
Conference Series
205 Institute of Physics
Publishing
Physics and Astronomy: General Physics and Astronomy Q4
IEEE Transactions on
Antennas and Propagation
197 IEEE Engineering: Electrical and Electronic Engineering Q1
Journal of Chemical Physics 193 American Institute of
Physics
Physics and Astronomy: General Physics and Astronomy
Chemistry: Physical and Theoretical Chemistry
Q1
Spectrochimica Acta Part A:
Molecular and Biomolecular
Spectroscopy
190 Elsevier Physics and Astronomy: Instrumentation
Optics
Chemistry: Analytical Chemistry
Chemistry: Spectroscopy
Q1
Journal of Materials
Chemistry C
189 Royal Society of
Chemistry
Materials Science: Materials Chemistry
Q1
Applied Catalysis B:
Environmental
176 American Institute of
Physics
Physics and Astronomy: Physics and Astronomy
(miscellaneous)
Q1
Optics Express 170 Optical Society of
America
Optics
Q1
Nanoscale 168 Royal Society of
Chemistry
Materials Science: General Materials Science Q1
Carbon 163 Elsevier Materials Science: General Materials Science
Q1
areas, especially mathematics and computer science, indicate that cer-
tain computational and numerical approaches have also been studied
in these areas [29–31]. Electromagnetic pollution is an environmental
problem that can be prevented using EM wave absorbers. Therefore,
environmental science focuses on EM pollution and its solutions as a
sub-research area [32].
4.4. The most productive countries and regions
The total number of published EM wave absorption documents for
the most productive countries and regions from 1990 to 2020 is shown
in Fig. 7. The increasing trend of the published documents on EM wave
absorbers is shown for the top 35 countries and regions. The obtained
data clearly demonstrates that China is the most productive country in
terms of published EM wave absorption documents with 8415 papers,
followed by the United States with 3600 papers. According to the annual
publication numbers, India (1874) and Japan (1711) are considered the
third and fourth most productive countries, each having more than 1000
publications total. The remaining countries and regions are listed as hav-
ing fewer than 1000 publications in terms of the published EMA studies.
Among these, the countries and regions with more than 500 documents
are as follows: Germany (965), the Russian Federation (896), France
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Fig. 6. Research areas of documents regarding EMAs published between 1990 and 2020.
Fig. 7. Distribution of publications around the world from 1990 to 2020
(889), South Korea (871), the United Kingdom (803), Italy (547), Iran
(502), and Canada (501). Highly industrialized countries and regions
with a developed defense industry have the top positions and dominate
EM wave absorption research. Chinese researchers can be seen to have
pioneered the field of EM wave absorption research. However, the ge-
ographical distribution of these countries and regions proves that the
trend of EM wave absorption research is not focused on any specific
geographical region.
4.5. Keyword analyses
The statistical evaluation of keywords is an effective bibliometric ap-
proach that can be used to analyze research trends and fields [33–35].
According to the results from the keyword analyses, the following three
main categories were formed: application and properties of EM wave
absorbers (EMAs), types of EMA materials, and the most studied EMA
materials, as shown in Figs. 8-10, respectively. The ability of materials
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Fig. 8. Distribution chart of the most-studied EM wave absorption materials.
to absorb EM waves depends on their electromagnetic and physical pa-
rameters, such as dielectric, magnetic, shape, impedance matching, and
polarization. Thus, various dielectric and magnetic nanofillers of vary-
ing sizes have been studied to reach acceptable absorption levels (−10
dB reflection loss attenuates approximately 90% of the incident wave).
Several types of dielectrics (carbon, graphene, polymers, and nonmag-
netic metal oxides) and magnetic fillers (iron, nickel, and ferrite) have
recently been studied as filler materials for EM wave absorbers. The
twenty most studied materials for EM wave absorption applications are
shown in Fig. 9. Titanium oxide (TiO2; 10%) and graphene (10.1%) have
excellent dielectric properties and are the most synthesized and char-
acterized materials in the field of EM wave absorption [36–41]. This
indicates that these materials have good dielectric properties and have
gained significant interest as EM wave absorbers [42,43]. Carbon-based
materials with superior dielectric properties are the third most studied
materials (7.8%), followed by other dielectric materials such as zinc ox-
ide (7%), silicon (6.3%), silver (6.1%), and glass (5.5%) [44–49]. The
dielectric and magnetic properties of a material determine its ability to
absorb, and the synergetic effects of the dielectric and magnetic values
provide better impedance-matching characteristics [50,51]. Therefore,
magnetic materials also maintain their position as important filler ma-
terials in EM wave absorption areas. Thus, iron compounds (4.6%) and
ferrite-based (4.2%) filler materials can be classified as the fourth group.
These types of filler materials with strong magnetic properties have re-
cently been studied alongside and independent of the dielectric materi-
als [52–54]. Carbon nanotubes (CNTs) (4%), copper (3.7%), and nickel
(3.6%) are the dielectric and magnetic materials used in most studies
[55,56]. The ability of a material to absorb EM waves can be enhanced
by good impedance matching and interfacial polarization effects [57].
Recently, the encapsulation of dielectric or magnetic fillers with con-
ductive polymers has gained significant interest owing to its high polar-
ization effect. Multilayer structures obtained using conductive polymer
coatings provide excellent absorption capabilities. Therefore, polymers
(3.5%) are among the most studied materials for EM wave absorption.
The other most studied dielectric magnetic and dielectric materials are
iron oxide (3.2%), magnetite (2.9%), silica (2.9%), zinc sulfide (2.8%),
and electrodes (2.8%).
Data regarding the properties and potential applications of the EM
wave absorbers were selected and are presented in Table 1 and Fig. 9.
Electromagnetic wave absorption is the most prevalent with 23439 oc-
currences, followed by optical properties (13113), reflection loss (9086),
photocatalysts (4524), and microwave absorption properties (3325). Re-
cently, EM wave absorbers have gained significant attention owing to
their other potential applications, such as in optical and photocatalytic
properties [58–60]. However, electromagnetic wave absorbers can also
be called microwave absorbers, which have the fifth highest prevalence
of occurrence in the literature. Although both keywords are the main
terms for EM wave absorption, we classified them into two separate
groups. Another important keyword is reflection loss, which expresses
the absorption ability in decibels (dB), wherein lower reflection loss val-
ues equate to a greater EM wave absorption ability (i.e., −20 dB of reflec-
tion loss absorbs approximately 99% of the incident EM wave and −10
dB absorbs 90%). The subclusters of electromagnetic wave absorbers
were analyzed for the five main selected topics, as shown in Fig. 10 and
Table 2.
Different types of EM wave absorbers have been synthesized and pre-
pared, including nanosized fillers, composite materials, and thin films.
The types of materials most studied with regard to EM wave absorption
are shown in Fig. 10, which demonstrates that EM wave absorbers are
mostly prepared as nanoparticles (16.6%), followed by thin films, photo-
catalysis, nanocomposites, nanocrystals, photocatalysts, dielectric mate-
rials, semiconductor quantum dots, metal nanoparticles, magnetic ma-
terials, single crystals, nanorods, composite materials, nanowires, and
dye-sensitized solar cells. Various categories have been found regarding
EM wave absorbers with respect to the types of filler, loss, and mate-
rial [61–64]. The size and shape of filler materials are among the most
important factors affecting the EM wave absorption performance [65].
Therefore, several types of filler materials have been studied, including
nanoparticles, nanorods, single crystals, semiconductor quantum dots,
and nanocrystals. The dielectric and magnetic properties of these fillers
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Fig. 9. The properties and applications of EM wave absorption materials.
Fig. 10. Distribution of the most studied materials.
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Table 2
The most frequently used keywords and their clusters
Potential application
and properties Supporting keywords
Electromagnetic
Wave Absorption
Electromagnetic Wave Polarization, Electromagnetic
Waves, Electromagnetic Wave Scattering,
Electromagnetic Parameters, Electromagnetic
Properties, Electromagnetic Wave Reflection
Optical Properties Absorption Spectroscopy, Light Absorption, Absorption
Spectra, Energy Absorption, Visible Light Absorption,
Optical Absorption, Visible-light Irradiation, Ultraviolet
Spectroscopy, Light, Energy Gap
Reflection Loss Dielectric Losses, Efficiency, Bandwidth, Permittivity,
Dielectric Materials
Magnetic Materials, Magnetism, Reflection, Dielectric
Properties, Magnetic Properties, Frequency Ranges,
Electric Conductivity, Complex Permittivity, Interfacial
Polarization, Polarization, Absorption Property,
Impedance Matching, Frequency Selective Surfaces
Photocatalysts Photocatalysts, Photocatalytic Activities, Photocatalysis,
Photocatalytic Performance, Photodegradation,
Luminescence, Catalysis, Photoluminescence,
Microwave
Absorbers
Microwave Absorption, Microwave Absorption
Properties, Effective Absorption, Power Conversion
Efficiencies, Specific Absorption Rate, Microwave
Absorbing Materials, Absorption Co-efficient,
Absorption property
(i.e., magnetic and dielectric loss materials) determine the type of loss
mechanism found in the absorber, such as the dielectric loss, magnetic
loss, and conductive loss. To achieve the desired performance, different
types of materials have been developed, such as thin films, composite
materials, and nanocomposites.
5. Conclusion
This study evaluated the last 30 years of progress regarding the po-
sition of electromagnetic wave absorbers (1990–2020) using a biblio-
metric approach based on 23213 published documents and 160 related
keywords. The annual progress in electromagnetic wave absorbers has
been summarized with respect to the countries and regions, citations,
published documents, keywords, and research fields. The results of this
study will provide detailed information for researchers focusing on elec-
tromagnetic wave absorbers. In conclusion, the key findings of this study
can be summarized as follows: The total number of publications and ci-
tations regarding electromagnetic wave absorbers demonstrated a sig-
nificant growth between 1990 and 2020. The remarkable increase in the
number of publications over the last ten years is noteworthy. A similar
growth trend was observed for the total citations. With respect to the
activity by countries and regions, China plays the leading role with a
total of 8415 published documents, followed by the United States with
3600. China, the United States, Japan, and India accounted for 53% of
the total publications. The most productive journal is the Journal of Al-
loys and Compounds with a total of 592 publications, followed by the
Proceedings of SPIE: The International Society for Optical Engineering
with 582. With respect to the data analysis considering the document
type, articles were the most preferred (80.4%), followed by conference
papers (17.6%). Only two of the top 20 journals have been observed
to have rankings other than Q1 on the Journal Citation Reports. The
top four sub-research areas were as follows: materials science, physics,
astronomy, engineering, and chemistry. However, the presence of sub-
research areas, such as mathematics and computer science, proves that
research regarding electromagnetic wave absorbers has been combined
with computational methods and theories. Another effective bibliomet-
ric approach is the keyword and keyword cluster analyses, which pro-
vides insight into the development and progress of a particular research
area. Nanoparticles have been identified as the most synthesized and
studied material type, followed by thin films and photocatalysts. The
most studied EM wave absorber is titanium oxide. The bibliometric ap-
proach in this study highlighted the annual growth trends, properties,
and development of electromagnetic wave absorbers in various aspects.
The results obtained from this study are expected to provide different
perspectives for the development of new electromagnetic absorbers.
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have influenced the work
reported in this study.
Acknowledgements
The data analysis in this study was supported by the Van YYU Uni-
versity Scientific Research Projects Coordination Unit. Project number:
FBG-2022-9858.
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