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The current manuscript introduces a dielectric regulated charge plasma based Triple metal Gate Tunnel Field Effect Transistor (CPB-TG-TFET) biological sensor. In which a nano-cavity is introduced below the gate and source electrode to detect the biological molecules like amino acids (AAs), protein, etc. The proposed P + and N + regions are contrived depending upon the electrode’s work function on the device’s silicon body. The effects of metal electrode work function modulation, gate electrode length variation and gate oxide thickness variation are analyzed for improving band-to-band tunneling efficiency at the source- channel transition. The proposed structure shows noticeable sensitivity results for neutral and charged biomolecules. The sensitivity of the neutral biomolecules having higher dielectric constant(Kp) is observed higher; the surface potential sensitivity of the Gelatin (Kp = 14) is estimated as 3 . × 10 10 which is 13% and 35% higher than the sensitivity of Keratin (Kp = 10) and Bacteriophage T7 (Kp = 5) respectively at the cavity length of 30 nm.

The effect of planar photonic crystal on CZTS/CdS solar cell is systematically investigated. The reflective properties of PhC ARC which consists of the periodic stack of ZnO and HfO2 with two numbers of periods having quarter wavelength thickness are analyzed. Similarly, the DBR having periodic stacks of HfO2 and ZnO dielectric layers with four numbers of periods having half wavelength thickness in CZTS/CdS solar cells are explored. Moreover, the results of the photovoltaic properties of CZTS/CdS solar cells are also analyzed. The outcome of the findings obtained from the computation using the transfer matrix method are very well agreeable with the recent literature. The planar (ZnO /HfO2)2 PhC ARC and (ZnO/HfO2)4 DBR has been expected to provide significant improvement in the performance of CZTS/CdS solar cells.

Rare-earth calcium oxyborate crystals (RECa4O(BO3)3, RECOB, RE: rare-earth elements) is a kind of multifunctional crystal materials. In this work, the temperature dependent behaviors of the electro-elastic constants for NdCOB crystal were investigated over the temperature range of –80–200 oC, and their temperature coefficients were evaluated. It is found that NdCOB possesses minimal variation of relative dielectric permittivities (

In the present work, samples of barium borate glasses containing different molar ratios of ZnO were prepared using the conventional melt-quenching technique. X-ray diffraction studies confirmed the amorphous nature of the studied materials. Structural analysis using FT-Infrared confirmed the incorporation of the Zn atom in the glass matrix as a ZnO4 unit and the existence of ZnO in the tetrahedral interstitial sites. TEM images for the studied materials show that the average particle size is about 20 nm and the ZnO4 structural units reside in the glass matrix with high homogeneity. Density and molar volume studies manifested an increase in the density as the amount of ZnO increases and a subsequent decrease in the molar volume. UV absorption studies showed a blue shift in the absorption peak from 343 nm to 315 nm. Additionally, an observed reversible behavior around 338 nm divides the absorption range into high energy and low energy regions. In the high energy region, both absorbance, absorption coefficient, and refractive index increased with ZnO content increment. In the low energy region, this behavior was reversed, and the calculated values of the refractive index agreed with the measured ones in this region. Studies of optical dielectric parameters showed a Debye-type relaxation process in which increasing the ZnO content shortens the sample relaxation time. Our results, collectively, suggest the studied materials for several optoelectronic device applications such as high-energy optical filters, optical switches, and frequency converters.

Yttrium aluminum garnet (YAG) with cerium admixture (Ce:YAG) was plasma sprayed using two different devices – gas-stabilized plasma (GSP) torch and water-stabilized plasma (WSP) torch. Coatings on stainless steel as well as self-standing plates were produced. Besides microstructure and crystallographic characterizations, dielectric tests were performed on these coatings. They included capacitance (i.e. relative permittivity), loss tangent and volume resistivity measurements. After spraying, the YAG crystal phase was preserved without any decomposition, but an amorphous fraction was detected in the as-sprayed coatings deposited by both processes. The dielectric behavior of the coatings was influenced by imperfections like splat boundaries, pores and thin cracks. The Ce:YAG samples were successfully plasma sprayed by both spray techniques. Selected aspects of wear were measured and compared with a single-crystal. The dielectric properties are comparable with the single-crystal and highly promising, particularly the loss tangent with values so low that they were not found in any other as-sprayed ceramic coating.

In this paper, the effect of Ba2+ ions A-site doping LaFeO3 on structure, magnetic properties and microwave absorption properties was investigated by the sol-gel method. According to the TEM and FullProf refinement results, the structure of LaFeO3 changes from orthogonal (SG: Pnma) to cubic (SG: Pm-3m) when the Ba doping amount is x = 0.4. The SEM image shows that the particles size tends to decrease with the increase of Ba content. The production of weak ferromagnetism indicates that Ba doping has a significant effect on the magnetic properties of LaFeO3. The Neel temperature (TN) decreases significantly with the increase of Ba doping amount. An appropriate amount of Ba doping can effectively increase the dielectric and magnetic loss of LaFeO3 ceramics powders. The increase permittivity (e′) may have been attributed to the hopping spin of the electrons between the Fe3+ and Fe4+ ions with the Ba2+ ions doping. The minimum reflection loss (RL) of La0.9Ba0.1FeO3 at 6.72 GHz reached –30.04 dB, its effective bandwidth (RL ≤ –10 dB) is 2.1 GHz, and the matching thickness is only 3.2 mm. These results indicate that Ba doping can effectively control the microwave absorption properties of LaFeO3, especially in the C-band.

To upgrade the electric properties of lead-free piezoceramics, (1–x)(Ba0.98Ca0.02Ti0.94Sn0.04Zr0.02)O3-xY2O3 (abbreviated as (1–x)BCTSZ-xY, x = 0 mol%, 0.02 mol%, 0.04 mol%, 0.06 mol%, 0.08 mol% and 0.1 mol%) ceramics were successfully synthesized by traditional solid-state sintering method. The phase structure and microstructure of ceramics were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and piezoresponse force microscopyeramics (PFM). The electric properties of ceramics were researched through piezoelectric, dielectric and ferroelectric test instruments. The results show that all samples have pure perovskite structure and favorable electric properties. The optimal electric properties which especially include superior ferroelectric properties are gained when Y2O3 content is 0.06 mol% (d33 = 419 pC/N, kp = 52%, Tc = 89.5 °C, er = 26900, tanδ = 2.86%, Pr = 14.41 μC/cm2, Ec = 1.8 kV/cm). Moreover, the temperature-dependent dielectricity of samples shows apparent relaxor behavior under different frequencies. The Curie–Weiss law further proves that all samples are typical relaxor ferroelectrics, and the relaxor degree of samples decreases with increase of Y2O3 content. In conclusion, Y2O3 plays a significant role in enhancing electric properties of BCTSZ ceramics.

In recent years, it has been found that the flexibility of structure and diversity of the components endow quite an amount of the organic-inorganic hybrid perovskites with novel properties, i.e., structural phase transitions. Considering the natural advantage of the perovskite-type structure in generation of stimuli-responsive or smart materials, we synthesized an organic-inorganic hybrid rare-earth double perovskite-type compound, (DMP)2LaRb(NO3)6 (DMP = N,N-dimethylpyrrolidinium cation, 1). It shows reversible phase transition at 219/209 K (heating/cooling). Variable-temperature single-crystal structure analysis and dielectric constant measurements reveal that the thermal vibrations of the polar cation guests and the distortion of the anionic cage-like framework are the origin of the phase transition. Meanwhile, the movement of polar cation in crystal lattices arouses dielectric transition between the low- and high-dielectric states, resulting in a switchable property of dielectric constant. The results reveal that the rare-earth double perovskite provides a promising platform for achieving switchable physical/chemical properties.

High discharged energy density and excellent flexible properties in dielectric materials are significantly sought to meet the rapid advancements in the electronics industry. In this study, covalent bonds are constructed between poly(vinylidene fluoride-chlorotrifluoroethylene), which contains olefinic bonds, and thiol-modified BaTiO3 at the interface before the nanocomposite films are fabricated. The presence of the covalent bonds is proved to promote the dispersibility of the modified BaTiO3 and enhance the interfacial adhesion between the modified BaTiO3 and the polymer, followed by a remarkably positive effect in suppressing the dielectric loss (tanδ) and increasing the breakdown strength (Eb) of the nanocomposite films. In addition, the cross-linking treatment in the preparation process is found to be favourable for improving the mechanical properties of the nanocomposite films, which benefits the enhancement of Eb. Furthermore, at 400% elongation, the stretched nanocomposite film doped with 5 vol% modified BaTiO3 exhibits an Eb 15.6% greater than that of the unstretched film, and the discharged energy density reaches 11.4 J/cm3 with a high discharge energy efficiency of 84.5%. This study provides a novel strategy for preparing flexible nanocomposites with powerful interfacial adhesion at high filler content to achieve high discharged energy density.

Materials that can efficiently absorb electromagnetic waves (EMWs) are required to deal with electromagnetic pollution. Structure design appears to be an efficient way to improve the EMW-absorption performance of such materials, particularly when adjustment of the constitution or mixing ratio is limited. In this study, bowl-like and honeycomb titanium dioxide/carbon nanotube (TiO2/CNT) composites with different CNT contents were fabricated using the methods of hierarchical and mixing vacuum-assisted filtration, respectively. Compared to the honeycomb structure, the bowl-like structure simultaneously facilitated greater interfacial polarization and conduction loss in favor of dielectric polarization, and augmented multiple reflections. The high porosity of the honeycomb structure was conducive to optimizing the impedance matching characteristics. The bowl-like TiO2/CNT composite exhibited a minimum reflection loss (RLmin) of −38.6 dB (1.5 mm) with a wide effective absorption band (EAB

Perovskite K(Ta,Nb)O3 (KTN) single crystal has drawn great interests for its outstanding electro-optic performance and excellent piezoelectric response. However, growth of compositionally uniform KTN single crystals has always been a great challenge for the great segregation difference between Nb and Ta. In this work, we propose a thermal field optimization strategy to resolve this challenge. Homogenous Sn doped KTN (Sn:KTN) single crystal with significantly reduced composition gradient (0.003 mol/mm, 1/4–1/8 of other KTN system), minimal TC variation (13 °C) and excellent piezoelectric and dielectric response (d33 = 373 pC/N and e 33 T = 5206) has been successfully achieved. We found that the functional properties of Sn:KTN were greatly affected by the near-room temperature tetragonal-cubic phase transition. From the intrinsic aspect, longitudinal lattice deformation becomes much easier, resulting in maximum piezoelectric ( d 33 ∗ ), dielectric ( e 33 T ∗ ), elastic ( s 33 E ∗ )and electromechanical coupling ( k 33 ∗ ) coefficients along polar direction [001]C. From the extrinsic aspect, both domain wall density and domain wall mobility are greatly improved for the reduced lattice distortion, which also contribute a lot to the functional properties. This work provides a simple and practical route for designing and growing high quality crystals, and more importantly, reveals the fundamental mechanism of the phase transitions/boundaries on the functional properties.

Dielectric polarization performance induced by defect engineering approach has been proved to be an effective way for improving the microwave absorption property of carbon-based materials. Assisting by the solid-state reaction, the structural integrity of multi-walled carbon nanotubes (MWCNTs) would be broken along with the volume expansion and etching process of cobalt oxides. Therefore, the defects could be obtained and result in the enhancement of microwave absorption property. Ascribing to the broken wall structures, the defect-distances (LD) and concentrations (nD) have been optimized to be 9.80 nm and 3.37 × 1011 cm−2. The minimum reflection loss (RL) had reached -54.6 dB at 4.5 GHz with a thickness of 4.13 mm and the corresponding effective absorption bandwidth (EAB

Nanoscale ruthenium (Ru)-based materials are promising replacements for existing multilayered Cu interconnects in integrated circuits. However, it is not easy to apply the results of previously reported studies directly to the electrochemical damascene process because the previous studies have mainly focused on thin films by dry deposition. Here, we report the electrical resistivity and microstructure of electrodeposited Ru nanowires. We estimate that the resistivity value of a 10 nm diameter Ru nanowire to be 71.6 μΩ cm after analyzing the resistivity values of individual nanowires with various diameters. Furthermore, we investigate the electrical properties of RuxCo1-x nanowires where x is 0.04–0.99 at.% as possible replacements of the current TaN barrier structures. Over the entire composition range, the resistivity values of alloys are much lower than that of the conventional TaN. Additionally, Ru and Ru-alloy nanowires surrounded by dielectric silica are thermally stable after 450 °C heat treatment. Therefore, the nanoscale Ru and Ru-Co alloys possessing low resistivity values can be candidates for the interconnect and barrier materials, respectively.

Perovskite LaCoO3 is of great potential in electromagnetic wave absorption considering its outstanding dielectric loss as well as the existing magnetic response with the magnetic doping. However, the dissipation mechanism of the magnetic doping on the microwave absorption is lack of sufficient investigated. In this paper, LaCo1-xFexO3 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, LCFOs) perovskites with different Fe doping amounts were prepared successfully by the sol-gel method and subsequent heat treatment in the air atmosphere. The structure characterization carried out by the first-principles calculations shows the effect of Fe doping on the dielectric and magnetic properties of LCFOs and the strong hybridization of Co/Fe-3d with O-2p in the LCFOs system was successfully demonstrated. Particularly, when x=0.1 and the thickness is only 1.95 mm, the LaCo0.9Fe0.1O3 exhibits the best microwave absorption performance with the minimum reflection loss (RL) value of about -41 dB. The typical samples achieve a broad effective absorption bandwidth (EAB) of 5.16 GHz (7.92-13.08 GHz), which covers the total X band (8-12 GHz). Considering that, the especial Fe doping perovskite is promising to be a candidate as efficient microwave absorbers.

Electromagnetic wave absorber is critical for reducing increasingly serious electromagnetic wave pollution, however, the development of lightweight and broadband microwave absorbers remains a pressing challenge. We report here the rational design and synthesis of N-doped Ni@SiO2/graphene composite constructed from 3D interconnected porous graphene network and Ni@SiO2 core-shell architecture, which fulfills lightweight and broadband requirements while exhibiting highly efficient electromagnetic wave absorption. The porous graphene network, functioning both as lightweight support and dielectric mediator, was synthesized via NaCl template-assisted high-temperature calcination method. Upon uniformly attached with core-shell Ni@SiO2 on the surface, the resulting abundant heterogeneous interfaces constructed by graphene-Ni and Ni-SiO2 strongly reinforce polarization loss. The presence of low dielectric SiO2 allows facile tuning of the complex permittivity of ternary composite by adjusting coating thickness to balance the attenuation ability and impedance matching. Moreover, further N-doping of graphene assists in the optimization of dielectric loss ability. Taking account of the advantages arising from the porous hierarchical architecture, multiple absorption centers and diverse interfaces, the lightweight composite exhibits an ultra-strong reflection loss (RL) value of - 71.13 dB at 13.76 GHz with a thickness of 2.46 mm and broad effective absorption bandwidth of 7.04 GHz at a low filler content of 15 wt.%. More importantly, the effective absorption range covers 13.28 GHz (4.72–18 GHz) with the optimized thickness of 1.6–5 mm, representing 83% of the whole range of frequencies. Our results demonstrate that the novel 3D porous N-doped Ni@SiO2/graphene network with hierarchical architecture is a promising candidate for high-performance electromagnetic wave absorption.

The inverse relationship between piezoelectric coefficient (d33) and depolarization temperature (Td) in Bi0.5Na0.5TiO3-based ceramics is a longstanding obstacle for their applications. In this work, synergistically enhanced d33 and Td is achieved in AlN-modified 0.84Bi0.5Na0.5TiO3-0.11Bi0.5K0.5TiO3-0.05BaTiO3 ceramics. Addition of 1 mol% AlN, increases both d33 from 165 to 234 pC/N and Td by ∼50 °C. Rietveld analysis of X-ray powder diffraction (XRD) data reveals an increase in the proportion of the tetragonal phase at 1 mol% AlN incorporation. Moreover, at this composition the modified ceramics exhibit larger grains and high-density lamellar nanodomains with sizes of 30–50 nm. Polarization reversal and domain mobility are thus significantly enhanced, contributing to the large d33. Temperature-dependent dielectric and XRD data revealed that the delayed thermal depolarization is attributed to the improved and poling-field stabilized tetragonality in the modified ceramics.

Microwave absorption (MA) materials have been captured extensive attentions due to the serious electromagnetic (EM) pollution. Numerous interests focus on the MA performances of core-shell structural composites with magnetic constituents as cores and dielectric constituents as shells, which inevitably suppressed the magnetic coupling causing the decrease of magnetic loss to some extent. Herein, the core-shell structural carbon (C) microsphere/magnetic metal composites were fabricated through the combination of an electrostatic assembly approach and subsequent in-situ reduction reaction. The complex permittivity and permeability of core-shell C@magnetic metal composite system can be effective adjusted by the constituent and microstructure of shells. Thanks to the distinct magnetic coupling from the subtle designed structures and the promotion of the magnetic-dielectric synergy, the C@magnetic metal composite exhibited enhanced MA properties. The optimal reflection loss (RL) of C@Ni composite was -54.1 dB with a thickness of 3.4 mm, meanwhile the effective absorbing band could reach over 5.5 GHz at only a 1.8 mm thickness. Broad absorption bandwidth with RL below -10 dB could achieve 6.0 GHz and 6.7 GHz for C@Co and C@NiCo composites with a thin 2.1 mm thickness, respectively. Our exciting findings might lead a guide on the novel structure design for the functional core-shell structural composites used for microwave absorption.

Al(8+x)/3O4-xNx (x = 0.299–0.575) transparent ceramics were fabricated by presintering and subsequent hot isostatic pressing (HIP) technology. The XRD and SEAD analyses verified that a complete solid solution with a cubic spinel structure was achieved in the entire composition range. The SEM characterization confirmed that the x = 0.299-0.510 samples are highly dense with rare residual pores, which was further demonstrated by HRTEM observations. In combination with phonon modes extracted by far-infrared reflectivity spectra, the intrinsic dielectric properties of AlON ceramics were estimated, which were consistent with the experimental results, revealing that the contribution to dielectric properties is dominated by the absorption of structural phonons. Moreover, as the nitrogen content increased, the measured permittivity (er) of the samples was found to gradually increase from 9.41 to 9.68 at 7 GHz, while the quality factor (Q × f) values fluctuated from 43750 to 76923 GHz. Accordingly, the reported AlON transparent ceramics with exceptional dielectric performances are promising candidates for high-frequency 5 G applications.

The dielectric layer plays a key role in regulating electromagnetic wave broadband scattering based on meta-surface technology. Herein, the physical properties of composite powder, prepared by spray drying of CaO-B2O3-SiO2 (CBS) glass-ceramic powder and Al2O3 in different mass ratios, are systematically investigated. Meanwhile, a high enthalpy atmospheric plasma spraying equipment is utilized to prepare CBS/Al2O3 composite coatings, and the morphology, physical properties and dielectric properties of the composite coating are analyzed. The XRD and DSC data of the composite coating reveal that the crystallization behavior of β-CaSiO3 and CaB2O4 gradually disappear with the increase of Al2O3 content. Hence, only CaAl2Si2O8 phase is observed during heat treatment. The experimental results confirm that the dielectric properties of CBS/Al2O3 composite coating conform to the rule of mixture for composite materials. Also, the dielectric properties are affected by porosity and crystallization rate.

Porous β-SiAlON ceramics are fabricated by pressureless sintering with Y-α-SiAlON ceramic powders obtained by the combustion synthesis method as the main additives. The microstructure and composition of porous β-SiAlON ceramics are tailored by changing the addition of the synthesized Y-α-SiAlON ceramic powders. The formation mechanism of porous β-SiAlON ceramics illustrates that their bimodal grain size distributions are determined by the β-SiAlON seed crystals which are derived from the starting synthesized powders and the first precipitates in the liquid phase, respectively. A small addition of Y-α-SiAlON is conducive to the reduction of the thermal conductivity of porous β-SiAlON ceramics. Furthermore, the higher the addition of Y-α-SiAlON ceramics powders, the lower the open porosity, columnar grain size, and dielectric loss, but the larger the density, flexural strength, dielectric constant, and thermal conductivity.

High-entropy ceramics (HECs) show outstanding properties such as amorphous-like thermal conductivities, colossal dielectric constant, superionic conductivity, enhanced electromagnetic wave absorption ability, super hardness and strength, which are promising for structural and functional applications. However, the high synthesis temperature has become the bottleneck that hinders the scale-up production and practical applications of HECs. It is thus appealing to develop a novel low-temperature process for the synthesis of HECs. To demonstrate the feasibility of low-temperature synthesis, herein, an electrospinning method has been utilized, for the first time, for the synthesis of high-entropy (Y0.2Yb0.2Sm0.2Eu0.2Er0.2)2O3 nanofibers. It has been found that after electrospinning from liquid precursors single phase (Y0.2Yb0.2Sm0.2Eu0.2Er0.2)2O3 solid solution with bixbyite structure can be formed by calcining at a temperature as low as 500 °C, which is at least about 1000 °C lower than that used in the solid-state synthesis method. The as-prepared (Y0.2Yb0.2Sm0.2Eu0.2Er0.2)2O3 nanofibers are continuous and uniform with a smooth surface and a small diameter of 150 nm. It is also intriguing that the average grain size of (Y0.2Yb0.2Sm0.2Eu0.2Er0.2)2O3 is only about 10 nm, which is much smaller than that in the solid-state synthesized powders. In addition, all the elements are homogeneously distributed along the nanofibers. This work demonstrates that high-entropy ceramic nanofibers can be synthesized from liquid precursors at low temperatures through a simple, efficient, and low-cost electrospinning method, which opens up a new avenue for the low-temperature synthesis of HECs.

Owing to the complex composition architecture of these solid solutions, some fundamental issues of the classical (1−x)Bi1/2Na1/2TiO-xBi1/2K1/2TiO3 (BNT-xBKT) binary system, such as details of phase evolution and optimal Na/K ratio associated with the highest strain responses, remain unresolved. In this work, we systematically investigated the phase evolution of the BNT-xBKT binary solid solution with x ranging from 0.12 to 0.24 using not only routine X-ray diffraction and weak-signal dielectric characterization, but also temperature-dependent polarization versus electric field (P-E) and current versus electric field (I-E) curves. Our results indicate an optimal Na/K ratio of 81/19 based on high-field polarization and electrostrain characterizations. As the temperature increased above 100 °C, the x = 0.19 composition produces ultrahigh electrostrains (> 0.5%) with high thermal stability. The ultrahigh and stable electrostrains were primarily due to the combined effect of electric-field-induced relaxor-to-ferroelectric phase transition and ferroelectric-to-relaxor diffuse phase transition during heating. More specifically, we revealed the relationship between phase evolution and electrostrain responses based on the characteristic temperatures determined by both weak-field dielectric and high-field ferroelectric/electromechanical property characterizations. This work not only clarifies the phase evolution in BNT-xBKT binary solid solution, but also paves the way for future strain enhancement through doping strategies. © 2021 The Chinese Ceramic Society. This work was supported by the National Natural Science Foundation of China (Grant Nos. 51772239 and 51761145024 ) and the Fundamental Research Funds for the Central Universities ( XJTU ). The SEM work was done at International Center for Dielectric Research (ICDR), Xi'an Jiaotong University, Xi'an, China.

Dielectric polymer composites with conducting fillers would have great potential for diverse applications if their severe leakage loss could be addressed. In this regard, ternary composites using both ceramic and conducting materials as fillers might be an enabler for high dielectric constant and low dielectric loss. Herein, ternary composites with both Ti3C2Tx MXene conducting nanosheets and CaCu3Ti4O12 (CCTO) dielectric particles embedded in silicone rubber were studied. It was found that a ternary composite with 1.2 wt% (0.40 vol%) Ti3C2Tx MXene and 12 wt% (2.58 vol%) CCTO could provide an overall superior performance that include a high dielectric constant of 8.8, low dielectric loss of less than 0.0015, good thermal stability up to 450 °C, and excellent mechanical properties with tensile strength of 569 kPa, elastic module of 523 kPa and elongation at break of 333%. The outstanding performance is attributed to the improved uniform dispersion and good interfacial compatibility of mixed fillers in the polymer matrix, suggesting ternary composites might be a better option over their binary counterparts in preparing high performance dielectric composites.

Yttrium oxide was sprayed by a plasma torch using a coarse thermal spray powder, which must be in size range of tens of micrometers to ensure good penetration into the plasma stream. Thick coatings on steel substrates were produced with two sprays systems facilitating gas stabilized plasma (GSP) and hybrid water-argon stabilized plasma (WSP–H) techniques. Additionally, an ultra-fine yttrium oxide powder was sprayed from a suspension. Hybrid water-argon stabilized plasma system was used for this purpose. Markedly thinner compact coatings were produced this way. All three sorts of plasma sprayed deposits were studied by the same methods. Dielectric properties were studied in a broad range of frequencies and temperatures. The microstructure aspects as well as crystallite size were analyzed and discussed in relation to electrical properties. All coatings exhibited stable dielectric parameters versus changing frequency and temperature, comparable with literature values for various samples. Concerning sintered bulks, and especially their thermal stability of capacitance, the plasma sprayed coatings were slightly worse. However due to shape and size variability of the plasma spraying are yttria coatings prospective for technical applications.

To ensure the porous Si3N4 ceramics with an excellent comprehensive performance for the application of radome, the commonly neglected effect of designed microstructures on dielectric and mechanical properties was investigated. Two typical porous Si3N4 ceramics with similar porosity but different microstructures (unidirectionally aligned and uniformly micropore structure with a different dimension of grains) were obtained by freeze casting and gel-casing process. The results indicate that the microstructure has a significant influence on the mechanical properties yet not an obvious effect on the dielectric properties, which means the dielectric constant can be reliably designed based on the porosity without consideration of different microstructures, meanwhile, the mechanical properties can be optimized by the microstructure. Besides, the results of the dielectric properties predicted by Finite Element Analysis show a high agreement with the experimental results. The study could be helpful to design a wave-transmitting component with integrated structure and function.

Ce2[Zr1-x(Zn1/3Nb2/3)x]3(MoO4)9 (CZ1-x(ZN)xM) (x = 0.02–0.08) compounds were successfully prepared to scientifically examine the effect of (Zn1/3Nb2/3)4+ doping on phase composition, microstructures, and properties. The XRD results showed that all compounds formed a pure phase with the space group of R-3c. SEM results indicated that all compounds were compact at 675 °C, and the lattice parameters and average grain size decreased with doping. Performance analysis illustrated that er was closely related to the polarizability, and Q∙f was affected by the lattice energy of the Mo–O bond. The τf was maintained at an excellent level. Far-infrared analysis indicated that the major dielectric contribution to CZ1-x(ZN)xM ceramics was related to the absorption of phonon oscillation. The optimum properties (er = 10.72, Q∙f = 59,381 GHz, τf = −11.48 ppm/°C) were obtained when x = 0.04.

BiFe1-2xZnxMnxO3 (BFZMO, with x = 0–0.05) thin films were synthesized via sol–gel method. Effects of (Zn, Mn) co-doping on the structure, ferroelectric, dielectric, and optical properties of BiFeO3 (BFO) films were investigated. BFZMO thin films exhibit rhombohedral structure. Scanning electron microscopy (SEM) images indicate that co-doping leads to a decrease in grain size and number of defects. Leakage current density (4.60×10−6 A/cm2) of BFZMO film with x = 0.02 was found to be two orders of magnitude lower than that of pristine BFO film. Owing to decreased leakage current density, saturated P–E curves were obtained. Maximum double remnant polarization of 413.2 μC/cm2 was observed for BFZMO thin film with x = 0.02, while that for the BFO film was found to be 199.68 μC/cm2. The reason for improved ferroelectric properties is partial substitution of Fe ions with Zn and Mn ions, which resulted in a reduction in the effect of oxygen vacancy defects. In addition, co-doping was found to decrease optical bandgap of BFO film, opening several possible routes for novel applications of these (Zn, Mn) co-doped BFO thin films.

Precursor derived ceramic with controllable carbon content has the advantages of high temperature and adjustable dielectric properties, which has significant potential for the research the high temperature microwave absorbing materials. In this contribution, a series of single-source SiBNCx precursors are obtained using NH3, n-butylamine, and dichlorodiphenylsilane with n-butylamine as the carbon source ammonolysis trichlorosilylamino-dichloroborane (TADB) monomer and polymerization. Adjusting the carbon content of precursors directly leads to phase composition and performance differences of SiBNCx ceramics. For SiBNCx ceramics with no carbon or low-carbon content, it had almost no effect on electromagnetic waves. The transmission rate ranged from 98% to 78% in 2–18 GHz. When SiBNCx ceramics with carbon-rich structure, the tanδ of pyrolytic ceramics increased significantly, which has an obvious loss on electromagnetic wave. The minimum reflection coefficient (RCmin) values reached −64.75 dB, and the effective absorption bandwidth (EAB) was 3.8 GHz in the X band at room temperature. Importantly, EAB of the SiBNCx ceramics still cover more than 50% of the X band, RCmin can be as low as −24.9 dB at 600 °C. The strategy offers a new method to accurately control high temperature electromagnetic performance from molecular structure.

The fabrication of high-performance electromagnetic (EM) wave absorption (EMA) materials is an effective strategy to deal with ever-increasing EM pollution. In this work, a series of manganese oxides/porous carbon (MnxOy@C) hybrid composites are obtained by a two-step process. It is revealed that different manganese oxides play various influence on the dielectric properties of absorbers. Owing to the moderate complex permittivity of MnO@C hybrid composites, the optimal reflection loss could reach as high as -76.0 dB at the matching thickness of 2.0 mm with 5.2 GHz of effective absorption bandwidth at thickness of 2.1 mm. We demonstrated that the addition of porous carbon is vital for enhancing EMA performance of composites, which not only coordinates impedance matching allowing more EM waves enter the absorber, but also provides the path for electron movement, thus profiting conductive loss. Besides, different heterogeneous interfaces including porous carbon, manganese oxide and so on, are conducive to contribution of interface polarization. The most noteworthy is ingenious design of composite materials and systematic research of EM energy attenuation mechanism in this work will provide the possibility to realize high-performance EMA.

The electromagnetic wave absorption (EMWA) performance of materials is affected by their dielectric and magnetic properties. Here, ferroferric oxide@N-doped residual carbon (Fe3O4@NRC) composites were successfully fabricated by decorating NRC with Fe3O4 nanoparticles via a facile chemical co-precipitation method. The RC was obtained through acid treatment to remove the inorganic minerals in coal gasification fine slag. The structure, composition, thermal stability, morphology, and related EM parameters of the as-fabricated Fe3O4@NRC composites were thoroughly tested via analytical techniques. Notably, both the Fe3O4@NRC-2 and Fe3O4@NRC-3 composites exhibited superior EMWA capacity. When 40% mass was added, the value of minimal reflection loss (RLmin) for Fe3O4@NRC-2 was −37.4 dB, and the effective absorption bandwidth (EAB, RL ≤ −10 dB) reached 4.16 GHz (13.84–18.00 GHz) at a thickness of 1.5 mm. Besides, the value of impedance matching was 1.00 as the RLmin was achieved. The results demonstrated that the EMWA performance of the composites could be adjusted by controlling the content of Fe3O4 nanoparticles. The magnetic/carbon composites exhibited superior EMWA performance, thus promoting the resource utilization of residual carbon in coal gasification fine slag from coal gasification.

Si3N4–BaTiO3 composite ceramics were prepared by hot pressing sintering. The effects of the amount of BaTiO3 and annealing process on the microstructure, phase composition, dielectric properties and thermal conductivity of Si3N4 composite ceramics were studied. With the increase of BaTiO3 content, the density and the dielectric performance of the Si3N4-based composite ceramics are improved, while the thermal conductivity is reduced. The annealing treatment can not only inhibit the growth of β-Si3N4, refine the grain, reduce the content of intercrystalline glass phase and porosity, but also promote the precipitation of hexagonal titanate barium, all of which are beneficial to increase the dielectric constant and decrease the dielectric loss, but will slightly reduce the thermal conductivity of Si3N4–BaTiO3 composite ceramic. The sample A2BT15 with 15% BaTiO3 sintered at 1750 °C for 2 h and annealed at 1300 °C exhibited the maximum dielectric constant (e = 10.57), the minimum dielectric loss (tanδ = 9×10-4), a high relative density (98.8%) and an acceptable thermal conductivity (14.5 W·m-1·K-1). Therefore, the selection of appropriate BaTiO3 content and annealing process can regulate the dielectric properties, thermal performance and mechanical properties of Si3N4–BaTiO3 composite ceramics in a certain range.

The rapid development of high technology—such as space exploration and electric vehicles—urgently requires ultra-wide temperature multilayer ceramic capacitors (UWT MLCCs) to achieve reliable operation of electronic circuits in harsh environments. However, simultaneously achieving high dielectric permittivity, low dielectric loss, and ultrahigh thermal stability has been a major challenge for practical dielectric ceramics. The co-firing matching of the internal electrode and the dielectric ceramic is also an important factor that affects the reliability of UWT MLCCs. Herein, through multifaceted modification—i.e., composition design related to the modulation of the local polar nanoregions (PNRs) and optimizing device sintering in the context of the compatibility of the heterogeneous interface—these concerns have been well-addressed. A new lead-free dielectric system (1-x) (0.56Na0.5Bi0.5TiO3-0.14K0.5Bi0.5TiO3-0.3NaNbO3)-xCaZrO3 (NKBTNN-xCZ) dominated by P4bm PNRs was designed and corresponding UWT MLCCs with reliable Pt internal electrode interface bonding were fabricated by optimizing the sintering temperature. A record-high dielectric permittivity (er = 839 ± 15 %) and low dielectric loss (tanδ ≤0.02) was achieved over an ultra-wide temperature range from -70 °C to 337 °C for NKBTNN-0.063CZ UWT MLCCs. This work suggests that multifaceted modification should be generalized for construction of high-performance UWT MLCCs.

In this work, we synthesized a novel and eco-friendly relaxor ferroelectric system, i.e., (1−x)(0.8Bi0.5Na0.4K0.1TiO3-0.2SrTiO3)-xNaNbO3 (BS-xNN) ceramics with x = 0.1–0.4 based on a solid state reaction technique. The structural, microstructural, dielectric as well as ferroelectric characteristics of BS-xNN ceramics were comprehensively examined. According to our findings, the Ti–O coupling reduces as the NN content increases, while the Nb–O coupling strengthens, leading in a nano-scale polarization mismatch-reestablishment process that enhances energy storage performance. Because of the reduction in thickness and porosity, the viscous polymer process significantly increases the breakdown strength of ceramic samples. More crucially, at 260 kV/cm, 0.6BS-0.4NN ceramics have an ultrahigh recoverable energy storage density Wrec of 4.44 J/cm3 and a high energy storage efficiency η of 81.8%. Furthermore, thermal stability of energy storage performance is also identified across a wide temperature range of 30 °C from 140 °C at 215 kV/cm. The higher performance of energy storage not only indicates the feasibility of our technique, but also serves as a model for the manufacturing of high-quality dielectric ceramics with a wide range of industrial applications.

Piezoelectric materials are widely used in electromechanical energy conversion, such as in sensors, transducers, and self-powered materials. In this paper, the influence of the Sm doping content on the microstructure and ferroelectric, piezoelectric, dielectric, and field-induced strain properties of 0.70Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PMN-PT) ceramics was investigated. Sm-doped PMN-PT ceramics with both high piezoelectric properties (d33∼1406 pC/N) and a large electromechanical coupling coefficient (kp∼0.69) were synthesized. Based on their piezoelectric effect, a maximum output voltage of 31 V was achieved under external forces. The output voltages showed satisfactory stability, repeatability, and sensitivity under periodic external forces; hence, Sm-doped PMN-PT piezoelectric ceramics are potential candidates for energy conversion and signal monitoring.

In this work, novel double perovskites RBaFeTiO6 (R = Pr, Nd) have been prepared through the sol-gel process. The structural, morphological, spectral, and dielectric behaviors were investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, dielectric measurements, and impedance spectroscopy. The objective of this work is to study these properties and investigate the effect of rare earth cations. XRD analysis confirmed the disordered cubic double perovskite structure of all prepared samples. The lattice parameters, bond lengths, and bond angles determined from the Rietveld refinement analysis are found to be dependent on the R3+ cation size. SEM and TEM micrographs indicated an irregular size distribution of the grains forming these double perovskites. The elemental composition and the stoichiometry of the prepared samples were verified by energy-dispersive X-ray spectrometer (EDX) elemental mapping. Raman and infrared spectroscopies have affirmed the influence of the rare earth element on vibrational properties and bond lengths. The dielectric properties were studied as a function of frequency. Electrical conduction follows Jonscher's universal power law and the conduction is attributed to the localized relaxation (reorientational) hopping mechanism. The presence of both negative (NTCR) and positive (PTCR) temperature coefficients of resistance in these materials is also affirmed by impedance spectroscopy.

The synthesis of a novel multicomponent perovskite was carried out by substituting 5 cations in the A-site of BaTiO3 lattice. The mechanochemical synthesis involved 5 h of ball milling followed by annealing at 800 °C for 2 h and the compound was sintered at 1200 °C for 2 h to form the cubic perovskite phase adopting the P m 3 ¯ m space group. The lattice parameter was found to be 0.391 nm. The reduction in the tetragonality and the local distortion in the compound were observed in the 2D charge distribution maps. The band gap of the compound was found to be 2.94 eV with a dielectric constant value of 270. Ferroelectric hysteresis loops were recorded and the leakage current density was found to be in the order of 10−5 A/cm2.

Relaxor ferroelectric polymers display great potential in capacitor dielectric applications because of their excellent flexibility, light weight, and high dielectric constant. However, their electrical energy storage capacity is limited by their high conduction losses and low dielectric strength, which primarily originates from the impact-ionization-induced electron multiplication, low mechanical modulus, and low thermal conductivity of the dielectric polymers. Here a matrix free strategy is developed to effectively suppress electron multiplication effects and to enhance mechanical modulus and thermal conductivity of a dielectric polymer, which involves the chemical adsorption of an electron barrier layer on boron nitride nanosheet surfaces by chemically adsorbing an amino-containing polymer. A dramatic decrease of leakage current (from 2.4 × 10−6 to 1.1 × 10−7 A cm−2 at 100 MV m−1) and a substantial increase of breakdown strength (from 340 to 742 MV m−1) were achieved in the nanocompostes, which result in a remarkable increase of discharge energy density (from 5.2 to 31.8 J cm−3). Moreover, the dielectric strength of the nanocomposites suffering an electrical breakdown could be restored to 88% of the original value. This study demonstrates a rational design for fabricating dielectric polymer nanocomposites with greatly enhanced electric energy storage capacity.

The bond, vibration and microwave dielectric characteristics of Zn1-x (Li0.5Bi0.5)xWO4 (x = 0–0.12) ceramics were investigated by XRD refinement, Raman and FT-IR spectroscopy and complex bond valence theory. The results showed that proper substitution of (Li0.5Bi0.5)2+ can improve the sintering characteristics and microwave dielectric properties of ZnWO4. The increase of Q×f value was mainly attributed to dense and uniform microstructure, and the subsequent decrease resulted from the deterioration of structural stability and relative density. According to the complex bond valence theory, the chemical bond characteristics of ZnWO4 and Bi2WO6 played an important role in the dielectric properties of the samples. Additionally, the samples (x = 0.02) sintered at 900 °C showed satisfactory properties: er = 15.332, Q×f = 35,762 GHz, and τf = −65 ppm/°C, making it a potential candidate material for LTCC applications.

In this paper, polymer composite (PC) film based on Methylcellulose (MC) has been prepared by solution cast technique and its optical bandgap was discussed in detail. X-ray diffraction (XRD) method , UV–Vis absorption spectroscopy and Fourier transforms infrared spectroscopy (FTIR) technique were used to study the effect of different concentrations of copper chloride (CuCl2) salt on the structural and optical properties of the MC polymer. Scanning electron microscopy (FESEM) is used to examine the effect of CuCl2 on films morphology. The fundamental optical parameters, such as optical energy gap (Eg), optical dielectric constant (er) and dielectric loss (ei) have been measured in which the amount of CuCl2 has significant effectiveness. Tauc’s relation was used to specifying the direct and indirect bandgap energy. The Eg of pure MC was considerably reduced from 6.21 to 2.68 eV by the addition of 20 wt% of CuCl2 salts. To specify the optical transition type, the exponent value of Tauc's law (γ) was identified by using the plot of ei against photon energy (hυ) to estimate the Eg value and specify the electronic transition type. For the composite samples, the Urbach energy (E0) increased, which can be evidence for a large possible number of tail-to-tail transitions. There is an increasing the refractive index (n) from 1.44 for pure MC to 2.04 upon the addition of 20wt.%CuCl2, indicating the occurrence of interaction between electrons and photons.

0-3 composites containing high permittivity ceramic particles and high breakdown strength polymer have aroused extensive concern for energy-storage application. In this research, flexible composite films were fabricated through incorporating of strontium titanate (SrTiO3) platelets (P-ST) and poly(vinylidene fluoride) (PVDF), and the effect of P-ST content on the dielectric and energy storage performances were researched systematically. It was found that at the relatively low electric field of 350 MV/m, the composite with 1 wt% P-ST exhibited an increased discharged energy density of 9.48 J/cm3, exceeding most of the current reports at the same electric field. And the distribution of local electric field and local polarization of composite films were simulated by COMSOL Multiphysics. This work provided a reference for polymer-based composite films featuring high energy storage property at relatively low applied electric field, which could reduce the possibility of failure for capacitors.

In the preparation process for advanced ceramics, how to reduce the sintering temperature, shorten the processing time and refine grains is the key to obtaining high-performance ceramic materials. The flash sintering (FS) provides an effective method to solve this issue. Here, (Zr + Ta) co-doped TiO2 colossal permittivity ceramics were successfully fabricated by conventional sintering (CS) and flash sintering under electric fields from 500 V/cm to 800 V/cm. The flash behavior, sintered crystal structure and microstructure, dielectric properties, and varistor characteristics were systematically investigated. The effects of the applied electric fields on the above behaviors were discussed. The results show that flash sintering can reduce the sintering temperature by 200 °C, decrease the processing time by 10 times and reduce grain sizes in TiO2 ceramics. All sintered samples were single rutile structures. Flash sintering led to similar electrical properties to conventional sintering. In the flash-sintered samples, with increasing the electric field, the permittivity of co-doped TiO2 ceramics increased at a frequency of 103–104Hz. The flash-sintered sample under an electric field of 800 V/cm possessed the best comprehensive properties, a dielectric permittivity of >105, a dielectric loss of ∼0.77 at 103 Hz, and a nonlinear coefficient of 5.2.

To explore the influence of TiO2 and B2O3 contents on the sintering behavior and crystallization of SrO–BaO–B2O3–SiO2 glass-ceramics, the glass-ceramics with different TiO2/B2O3 ratios were prepared by sintering at 800 and 850 °C for 10 min. The results showed that the glass transition temperature and sintering temperature increased with increasing the TiO2/B2O3 ratio. The average bridging oxygen number decreased from 2.44 to 2.07, which revealed that the polymerization degree of the glass-ceramics decreased. With increasing the TiO2/B2O3 ratio, the crystallinity of the glass-ceramics and the homogenization of grains size were improved, and the precipitation of the SrTiO3 phase was promoted. The sample with a TiO2/B2O3 ratio of 0.62, which achieved excellent densification sintered at 850 °C for 10 min, showed a dielectric constant of 18.11, a dielectric loss of 3.93 ×10−3, and a thermal expansion coefficient of 10.04×10−6 K−1, indicating that the SrO–BaO–B2O3–SiO2 glass-ceramics have great potential in the application of low-temperature cofired ceramics.

The influence of grain size on the dielectric properties of Sr0.6Ba0.4Nb2O6 (SBN60) ceramics with a tetragonal tungsten bronze structure was examined. The conventional and two-step sintering procedures were used to fabricate dense and phase-pure SBN60 ceramics with grain sizes ranging from 2.2 μm to 17.3 μm. In the temperature dependence of the dielectric permittivity, all samples showed a relaxor-like broad dielectric peak with a maximum at around 60 °C. The maximum dielectric permittivity and dielectric maximum temperature of the SBN ceramics were found to be less dependent on the grain size. The reason for the grain-size-insensitive dielectric properties of the SBN60 ceramics is discussed based on the analysis of the dielectric properties and Raman spectra.

With the development of energy-storage technology and power electronics industry, dielectric capacitors with high energy density are in high demand owing to their high power density. Especially for ferroic dielectrics (including ferroelectrics and antiferroelectrics) showing dipole moments in the perovskite unit cells, large dielectric response under electric fields makes them own outstanding potentials for achieving high energy-storage density. Particularly, destroying long-range ferroelectric/antiferroelectric ordering by enhancing compositional disorder is found to be effective for extremely improving energy-storage properties (both high recoverable energy-storage density and efficiency), because these macroscopic-nonpolar nanodomains are highly polarizable under strong external electric fields. Moreover, owing to the heterogeneous structure induced dielectric relaxation characteristics, excellent temperature stability can be achieved simultaneously. The recent developments of (anti)polar nanoregions with different possible local symmetries in various lead-free perovskite-structured dielectrics have been summarized in this review, together with the achieved energy-storage properties based on them. This review would provide a guidance for preparing high-performance energy-storage capacitors by local-structure engineering for next-generation pulse power applications.

The increasingly severe electromagnetic microwave pollution raises higher requirements for the development of efficient microwave absorption (MA) materials. Metal sulfides are regarded as potential robust MA materials because of their unique optical, thermal, electrical, and magnetic properties, as well as the controllable microstructures. However, due to the limited MA performances of unary metal sulfides, morphology regulations and foreign materials hybridizations are adopted as effective strategies to improve their MA performances. Recent years witnessed the fast research progresses on the metal sulfides based MA materials and thus, a systematic literature survey on the materials design, fabrication, characterizations, MA behaviors, and the mechanisms behind is, highly desirable to summarize the rapid progress of this hot research area so as to provide guidance for the future development trend. This review firstly reviewed the research background, research progress, and basic principles of MA materials. Subsequently, the present synthetic methods and performance improvement strategies of metal sulfides based MA materials are systematically introduced. Then, by comparing the MA properties of one-dimensional, two-dimensional, and three-dimensional metal sulfides based composites, the influence of dimensionality and morphology on the MA properties are analyzed. By summarizing the research process of metal sulfides/dielectrics composites, metal sulfides/magnets composites, and metal sulfides/dielectrics/magnets composites MA materials, the influence of foreign materials hybridizations on the loss mechanisms and impedance matching conditions of metal sulfides based composites are revealed. Finally, the challenges and development prospects of metal sulfides based MA materials are presented. This review would provide a comprehensive understanding and insightful guidance for the exploration and development of efficient MA materials with thin thickness, light weight, wide absorption bandwidth, and strong absorption intensity.

Lead-free ceramic capacitors have the application prospect in the dielectric pulse power system due to the advantages of large dielectric constant, lower dielectric loss and good temperature stability. Nevertheless, most reported dielectric ceramics have limitation of realizing large energy storage density (Wrec) and high energy storage efficiency (η) simultaneously due to the low breakdown electric field (Eb), low maximum polarization and large remanent polarization (Pr). These issues above can be settled by raising the bulk resistivity of dielectric ceramics and optimizing domain structure. Therefore, we designed a new system by doping (Bi0.5Na0.5)0.7Sr0.3TiO3 into 0.9NaNbO3-0.1Bi(Ni0.5Zr0.5)O3 ceramics, which simultaneously obtained a higher bulk resistivity by decreasing the grain size and achieved a smaller Pr by optimizing domain structure, thus the better Eb of 530 kV/cm and Wrec of 6.43 J/cm3 were achieved, η was improved from 34% to 82%. Besides, the 0.4BNST ceramics show excellent temperature, frequency and fatigue stability under the conditions of 20–180 °C, 1–100 Hz and 104 cycles, respectively. Meanwhile, superior power density (PD = 107 MW/cm3), large current density (CD = 1070 A/cm2) and discharge speed (1.025 μs) were achieved in 0.4BNST ceramic. Finally, the charge-discharge performance displayed good temperature stability in the temperature range of 30 °C–180 °C. The above results indicated that the ceramics have potential practical value in the field of energy storage capacitor.

Fe2O3 thin films were deposited by Successive Ionic Layer Adsorption and Reaction (SILAR) method onto glass substrates at different cycle numbers to investigate structural, linear and nonlinear optical properties. X-Ray Diffraction (XRD) analysis revealed that the Fe2O3 thin films have a non-crystalline nature. The morphological properties of the films were investigated by Field Emission-Scanning Electron Microscopy (FE-SEM) and the results show that the films’ surfaces are porous. The linear and nonlinear optical parameters were evaluated and analyzed by using transmittance and absorbance measurements. For these measurements, UV–Vis spectroscopy at room temperature was used. The refractive index values were calculated in the range of 1.45–3.23 for visible region (400–700 nm). Obtained results reveal that direct optical band gap changed between 2.62 and 2.68 eV and indirect optical band gap changed between 1.67 and 1.77 eV. Additionally, optical electronegativity, optical dielectric constants, surface and volume energy loss functions, nonlinear refractive index, linear optical susceptibility, third-order nonlinear optical susceptibility, optical and electrical conductivity, and loss tangent values were calculated and discussed in detail. It was found that each parameter studied is dependent on the cycle numbers. Also, it can be stated that Fe2O3 thin films are promising candidate for solar cells and optoelectronic device technology.

In this paper, the effects of hot isostatic pressing (HIP) temperature on the crystal structure, optical, dielectric and magnetic properties of GdMnO3 ceramics were studied. All samples form a single-phase structure without structural transformation, while HIP temperature induces the changes in lattice parameters. HIP causes the change in Mn ions valence state, oxygen vacancy concentration, Raman vibration modes and microscopic morphology of GdMnO3. Vacancy concentration of the samples prepared by HIP at 800 °C increases compared with that of the samples without HIP, then remains unchanged when the HIP temperature is from 800 to 900 °C, and finally decreases with the further increase of HIP temperature. Appropriate HIP temperature can increase the dielectric constant and decrease the dielectric loss. The transition temperature of paramagnetism to antiferromagnetism and magnetization can be significantly affected by HIP temperature. Magnetic transition temperature and magnetization are closely related to Mn2+ ions concentration and cation vacancy concentration, respectively.

In order to overcome the problems caused by electromagnetic pollution, the design and development of high-performance microwave absorbers is urgently required. In this work, a hierarchical ZnFe2O4@MnO2@RGO composite was successfully fabricated via a facile and rapid hydrothermal method. Its unique core-shell structure and synergistic effect between multiple components are beneficial for electromagnetic wave absorption. The morphology, elemental composition, microstructure and microwave absorption characteristics were systematically studied. With a filler loading of 20 wt%, the composite presents a minimum reflection loss (RLmin) of −46.7 dB and an effective absorption bandwidth (EAB) as wide as 5.2 GHz at a thickness of 2.5 mm. The superior absorption ability profits from a special microstructure, good impedance matching, multiple attenuation features, interfacial polarization, and the synergistic effect of dielectric and magnetic loss. Consequently, this work lays a foundation for the design of high-performance electromagnetic wave absorbers with multicomponent heterogeneous structures.