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The type of multi-component fillers and their spatial distribution in conductive polymer-based composites greatly influenced their electrical properties, electromagnetic shielding efficiency (SE), and absorption capability, which require a deep understanding of how these properties improve with changes in the phase composition, content, and distribution of these fillers in the composite. In this study, three-phase polymer composite materials (CMs) with random (epoxy-based) and segregated (polyethylene-based) distribution of nanocarbon (graphite nanoplatelets GNP and carbon nanotubes CNTs) and magnetic (Fe and Co3O4) fillers have been developed. It was found that permittivity ε r ′ in the frequency range (40–60 GHz) increases sufficiently with the nanocarbon content and their values are slightly higher for random GNP-filled CMs (ε r ′ = 10 – 15 for 3–5 wt. % GNP) compared to CNT-filled CMs and much higher compared to segregated CMs (ε r ′ = 4 – 7 for 3–5 wt. % of nanocarbon). Dielectric loss tangent tan δ is increased with the nanocarbon content (especially for Fe-filled CMs) and sufficiently higher in segregated CMs compared to similar random composites. These enhanced tan δ values correlate with higher electromagnetic shielding efficiency due to absorption of segregated nanocarbon/magnetic/polyethylene CMs, for example, SEAd ≈ 18–23 dB/mm for 5 wt. %GNP. The most preferable for microwave absorption are random and segregated CMs with 2–3 wt. % GNP/30 wt. % magnetic filler: RLmin = −(27–35) dB, effective absorption bandwidth (EAB) Δ f 10 dB = 11.5 – 12.5 GHz at a sample thickness of 0.5–0.7 mm. In CNT-based segregated CMs, | R L min | and EAB values are lower compared with GNP-based CMs. The ability to manipulate these characteristics is important for obtaining good shielding and absorptive properties in the microwave range of electromagnetic radiation. [ABSTRACT FROM AUTHOR]

Epoxy dielectrics with high through-plane thermal conductivity (λ) hold great promise for applications in the thermal management of advanced power electronics. Intensive attempts have been made to improve the λ of epoxy by filling with boron nitride nanosheets (BNNSs). However, it remains a great challenge to achieve a satisfactory increased λ by a small amount of BNNS loading. Herein, we reported a new strategy to prepare epoxy dielectrics with internal three-dimensional phonon transport channels by vacuum freeze-drying and vacuum impregnation. Aramid nanofibers (ANFs) and BNNSs were used for the collaborative construction of a vertical interconnected thermal framework. The resultant ANF-BNNS/epoxy achieved a high through-plane λ of 0.87 W m−1 K−1 at only 1.43 vol. % BNNS, which is ∼17.1% higher than that of the BNNS/epoxy counterpart with even 18.34 vol. % randomly distributed BNNS. The increasing efficiency of λ of epoxy by ANF-BNNS is tenfold more than that of the conventional blending methods. In addition, the ANF-BNNS/epoxy composite also exhibits a low dielectric constant and low dielectric loss. The findings of this study offer an inspired venue to develop high-performance thermally conductive epoxy dielectrics with a minimal BNNS loading. [ABSTRACT FROM AUTHOR]

In a class of high quality (Q-) factor dielectric resonators with low radiative losses, including popular whispering-gallery mode (WGM) resonators with high azimuthal mode numbers, due to high confinement of modal field in dielectric, the Q-factor is limited by the value of inverse dielectric loss tangent of dielectric material. Metal enclosures necessary for device integration only marginally affect the Q-factor while eliminating the residual radiative loss and allowing the optimization of input and output coupling. While very high Q-factors ∼ 200 000 are available in sapphire WGM resonators in X-band, at millimeter wave frequencies increasing dielectric loss limits the Q-factor to much smaller values, e.g. ∼50000 and ∼25000 for quasi-TE and quasi-TM modes, correspondingly, at 36 GHz. The use of distributed Bragg reflection (DBR) principle allows to push modal energy outside dielectric while also isolating it from Joule losses in metallic enclosure walls. Very high Q ∼ 600 000 > --> t g δ has been demonstrated in X-band [C. A. Flory and R. C. Taber, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 44, 486–495 (1997).] at the expense of impractically large dimensions. In this work, we report on the assembly and testing of a compact Ka-band sapphire distributed Bragg reflector cavity characterized with Q-factor seven times larger than one predicted by the material's dielectric loss at the frequency of interest. An intrinsic Q-factor of ∼ 200 000 is demonstrated at 36 GHz for the lowest order TM-mode of a sapphire DBR. The resonator has 50 cm 3 volume, smaller than previously demonstrated DBRs. [ABSTRACT FROM AUTHOR]

The microstructure morphology, static magnetic properties, and electromagnetic absorption characteristics of nano FexCoNi alloy particles prepared by chemical liquid deposition with five different Fe content levels are investigated in this paper. The results show that spherical FexCoNi alloy particles with an average particle size of about 100–200 nm and a face-centered cubic crystal structure were obtained. All five samples exhibited soft magnetic behavior, with the saturation magnetization intensity showing an increasing-then-decreasing trend with increasing Fe content, peaking at 141.8 emu/g for Fe content x = 1.0. The dielectric constants (real and imaginary parts) of the prepared alloy particles exhibit significant differences with respect to the variation of Fe content, while the changes in the real and imaginary parts of the magnetic permeability show less pronounced effects with increasing Fe content. As the electromagnetic wave frequency increases, the real parts of the dielectric constants for all composites show minimal fluctuations, and the real parts of the magnetic permeability exhibit a decreasing trend. Moreover, the imaginary parts of the dielectric constants and magnetic permeability show an increasing followed by a decreasing trend as the frequency rises. The material with Fe content x = 1 demonstrated optimal dielectric loss performance and relatively excellent magnetic loss performance, with a sample thickness of 1.9 mm exhibiting the highest reflection loss (RLmax) of −24.2 dB and an effective absorption bandwidth of 4.48 GHz. [ABSTRACT FROM AUTHOR]

Measurement of high-temperature physical properties at microwave frequency is important to interpret the heating behavior of NiO observed in the author's previous studies. In this study, the impedance (4 Hz–5 MHz) and permittivity [at the microwave frequency (2.45 GHz)] of NiO powder particles were measured from room temperature (RT) to 800 °C. At high frequency above 100 kHz, the conductivity is almost independent of temperature up to a certain temperature (Ti). Above Ti, the conductivity showed a strong positive dependence on the temperature. In this region, the apparent activation energy is determined to be 0.51 eV, which is close to that of the previously reported large polaron transport mechanism (band-like conduction). It was also shown that the conductivity increased linearly with frequency and that a dielectric conductivity relation (σ = ωε″) holds, which is different from the hopping mechanism of the small polaron. Considering these results, it was understood that the temperature increase occurred preferentially in the microwave E-field. The slow increase from the room temperature is due to a small but finite dielectric loss at room temperature, and because of the low conductivity, induction current is not effectively generated in the H-field. On the other hand, after a certain time, the temperature rises to reach the large temperature-dependent conductivity, and then, a significant temperature rise occurs. [ABSTRACT FROM AUTHOR]

Glassy films of methyl-m-toluate have been vapor deposited onto a substrate equipped with interdigitated electrodes, facilitating in situ dielectric relaxation measurements during and after deposition. Samples of 200 nm thickness have been deposited at rates of 0.1 nm/s at a variety of deposition temperatures between 40 K and Tg = 170 K. With increasing depth below the surface, the dielectric loss changes gradually from a value reflecting a mobile surface layer to that of the kinetically stable glass. The thickness of this more mobile layer varies from below 1 to beyond 10 nm as the deposition temperature is increased, and its average fictive temperature is near Tg for all deposition temperatures. Judged by the dielectric loss, the liquid-like portion of the surface layer exceeds a thickness of 1 nm only for deposition temperatures above 0.8Tg, where near-equilibrium glassy states are obtained. After deposition, the dielectric loss of the material positioned about 5–30 nm below the surface decreases for thousands of seconds of annealing time, whereas the bulk of the film remains unchanged. [ABSTRACT FROM AUTHOR]

The search for a high- κ dielectric material that combines a high dielectric constant (ϵ ′ ) and low dielectric loss is very crucial because of its widespread use in gate dielectrics to avoid the leakage current that arises due to continued miniaturization of present SiO 2 -based metal-oxide semiconductor field-effect transistor devices. RCrO 3 (R is a rare-earth ion) materials have been at the center of interest because of their intriguing ferroelectric and magnetic properties, as well as their room-temperature colossal dielectric constant (CDC) values. Although CDC (ϵ ′ ∼ 10 4) in RCrO 3 materials is quite common, it is unsuitable for device applications since it is associated with a larger dielectric loss value (tan δ ∼ 7 at 11 kHz). Here we have focused on polycrystalline DyCrO 3 , prepared using multiple synthesis techniques, and thoroughly investigated the origin and tuning of the various dielectric relaxations that give rise to CDC and large dielectric loss values. A clear understanding of the origin of dielectric relaxations enables us to design a specially synthesized DyCrO 3 (SPS-DCO) in which the extrinsic dielectric relaxations driven large dielectric loss values can be completely suppressed and which is found to be associated with optimized high- κ dielectric properties [ ϵ ′ ∼ 130 , tan δ ∼ 0.06 , and temperature coefficient of dielectric constant (TC ϵ) ∼ 2280 ppm/K at 11 kHz, 300 K]. The only remaining intrinsic Debye-type dielectric relaxation in SPS-DCO arises due to electric-field-assisted charge hopping among various valences of Cr (investigated using x-ray photoelectron spectroscopy) that presently limits the lowest attainable loss value. [ABSTRACT FROM AUTHOR]

Environment-friendly piezoelectric micro/nanogenerators have attracted tremendous attention due to the increasing demand for portable self-power devices. Here, the [(0.94−x)Bi 0.5 Na 0.5 TiO 3 –0.06BaTiO 3 –xK 0.5 Na 0.5 NbO 3 ; BNT-BT-xKNN] lead-free ceramic, at x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10 mol%, was prepared via the solid-state method. The doping concentration x = 0.02 mol% shows the highest dielectric properties and the lowest dielectric loss. The active layer of the hybrid device is made by mixing BNT-BT-2KNN into the PDMS to form a series of polymer-ceramic composite films ranging from 7 to 19 wt% of BNT-BT-2KNN. The electrical response of the composite film is systematically studied with the addition of different weight percentages of the particles to the PDMS matrix. It was found that incorporating BNT-BT-2KNN at 11 wt% into the PDMS matrix exhibited the optimum harvesting performance, resulting in an output voltage and current density of about 30 V and 0.28 μA/cm2, respectively. The hybridized PENG and TENG devices could operate in a long-term cyclic mode, charge the capacitor for energy storage, and also light up LEDs. This research proposed a simple device fabrication and provided a guideline for the development of high-performance microgenerators, which is crucial for device development and practical use in the future. [ABSTRACT FROM AUTHOR]

The dielectric loss (tan δ) value of stoichiometric SrTiO 3 (ST), prepared using the solid-state reaction method, exhibits a random variation between 0.0006 and 0.01968 at room temperature and a frequency of 1 kHz in the literature. This variability makes it challenging to obtain reliable and reproducible performance for ST-based devices, especially when the underlying reasons are not yet completely understood. This work reports the significant effects of different raw materials, with various forms of TiO 2 , on the dielectric and electrical properties of ST ceramics. The results show that the purity of SrCO 3 and TiO 2 ultimately leads to distinct differences in dielectric properties, impedance properties, activation energy across the ST ceramics. Crystal comparison demonstrates that anatase TiO 2 is more suitable for dielectric applications. These results provide a reasonable explanation for the large variations in reported ST properties in the literature, which emphasizes the critical importance of selecting suitable reagents in ST-based ceramics. This insight opens up a new avenue for design optimization and highlights the promising potential of ST-based ceramics. [ABSTRACT FROM AUTHOR]

To design novel materials suitable for high-temperature electromechanical applications, a bismuth-based ternary solid solution system, (1- x - y)BiScO 3 - y Pb(Sc 1/2 Nb 1/2)O 3 - x PbTiO 3 , with compositions situated around the morphotropic phase boundary, were designed and synthesized in the form of ceramic. The crystal structure, microstructure, dielectric, ferroelectric and piezoelectric properties, and the local polar domain structure of the ceramics were investigated in detail. The examined ceramics exhibit large grain sizes ranging from 20 μm to 45 μm, along with noteworthy characteristics, including a relatively large strain of 0.21 %, a high large-signal piezoelectric coefficient (d 33 * = 368 pm/V), a low dielectric loss (tanδ = 1.7 %), and a high Curie temperature (T C ∼ 423 °C). These enhanced properties signify the suitability of the designed ternary ceramics for future high-temperature electromechanical applications. This work demonstrates an effective approach for designing ferro-/piezoelectric materials characterized by substantial strain and low dielectric loss. [ABSTRACT FROM AUTHOR]

Colossal permittivity (CP, Ɛ r) ceramics are highly desired for promising applications in modern electronic industry. However, actual applications of CP ceramics were seriously limited by large dielectric loss (tan δ), strong temperature/frequency/electric field dependence, and resistance degradation behavior. Here, we proposed a novel strategy to inhibit the diffusion of oxygen vacancies to obtain a CP Sr 0.979 Y 0.014 TiO 3 (SYT14) ceramic with a combination of low tan δ and high insulation resistivity (ρ), by MgO addition, due to the formation of [ M g T i ″ − V O • • ] , [ M g T i ″ − 2 Y S r • ] and highly insulated phase at the grain boundary. SYT14-7 M (x = 0.7 wt% MgO) ceramic has excellent comprehensive properties, such as, Ɛ r is 28156, tan δ is 0.0136, and ρ is 7.02 × 1011 Ω cm. The phenomenon of "resistance oscillation" reflects the active degree of oxygen vacancy diffusion behavior. The highly insulated phase forming at the grain boundary can significantly inhibit oxygen vacancy diffusion and electron migration. The temperature range related to active oxygen vacancy diffusion is between 400 and 500 °C. [ABSTRACT FROM AUTHOR]

The Nb-doped SrTiO 3 (SNT) ceramics were prepared using the traditional solid-state reaction method. It was observed that the room temperature permittivity exhibited a significant increase from 102 to 104 as the partial pressure of oxygen in the sintering atmosphere gradually decreased. To elucidate the mechanism driving these observed changes in permittivity, the microstructure and dielectric properties of SNT ceramics were investigated. The results indicated that the presence of Ti3+/Ti4+ polar structure and the defect dipole [ Ti 4 + ∙ e − V o ∙ ∙ − Ti 4 + ∙ e ] resulted in the increase of permittivity, but only [ Ti 4 + ∙ e − V o ∙ ∙ − Ti 4 + ∙ e ] can reduce dielectric loss. The formation and concentration of these defects were influenced by the oxygen partial pressure in the sintering atmosphere, consequently influencing the alteration in the permittivity. [ABSTRACT FROM AUTHOR]

The dielectric and energy storage properties of (1- x)(0.7(Bi 0.5 Na 0.5)TiO 3 -0.3(Sr 0.7 Bi 0.2)TiO 3)- x Bi(Mg 0.5 Zr 0.5)O 3 (BNT-SBT- x BMZ) ceramics are systematically investigated, and further modified by using the strategy of doping two kinds of sintering aids, LiF and B 2 O 3 –Bi 2 O 3. The results show that all ceramics exhibit a typical perovskite structure. The doping of sintering aids reduces the sintering temperature effectively to below 1000 °C and obtains the dense microstructure. Meanwhile, the ferroelectric long-range order can be disrupted that facilitates the polarization in nano-regions at high temperatures induced by LiF dopants, which enhance the relaxor behavior and form a dielectric platform together with low dielectric loss in a wide temperature range. In addition, extremely slender polarization-electric field (P - E) hysteresis loops are gained by doping LiF in BNT-SBT- x BMZ ceramics associated with an almost non-polar phase that exhibits linear response. In comparison, little change in shape of P - E loops is observed when adding B 2 O 3 –Bi 2 O 3. As a result, outstanding energy storage performances are achieved in sintering-aids modified ceramics under the relatively low electric fields of 180 kV/cm −210 kV/cm. This work provides the optimized energy storage properties and dielectric stability of BNT-based ceramics at reduced sintering temperatures, and pave the way for the cofiring with base metal electrodes in multilayer ceramic capacitors. [ABSTRACT FROM AUTHOR]

In this work, we synthesized composites of ferrous disulfide and tin disulfide with multi-walled carbon nanotubes (MWCNTs) using a straightforward hydrothermal method. The incorporation of carbon nanotubes significantly enhanced the dielectric loss capability of the composites. When the filling ratio of FeS2/SnS2@CNTs (20 wt%) in paraffin was 40%, the effective absorption bandwidth was 3.28 GHz, while the minimum reflection loss (RL) value was as high as −39.2 dB, which corresponded to a thickness of only 1.4 mm. This work reveals the potential research value of this material in terms of thin thickness, strong absorption and light mass. [ABSTRACT FROM AUTHOR]

Ba 1.5 Sr 0.5 Zn 2 Fe 28-x Yb x O 46 (x = 0.00, 0.07, 0.14, 0.21, and 0.28) hexaferrite were synthesized via sol-gel auto-combustion route to investigate the microwave absorption performance in different frequency bands. The structure has a single phase, and the variation in lattice parameter was observed due to Yb-content as host iron Fe3+ and substituted Yb3+ having different ionic radii. Microwave absorbing materials (MAMs) need to be lightweight, and the maximum crystallite size of prepared material is 41 nm. The physical properties vary with substitution, and the X-ray density value is higher than the bulk density, and the porosity of the prepared sample increases when the bulk density decreases. Micro-strain values are inverse to the crystallite size because Yb3+ has larger ionic radii than Fe3+. Rietveld refinement of the XRD patterns was conducted with a lower significance value. FTIR bands observed between 414 and 500 cm−1 are present due to iron-oxygen bond stretching and bending vibrations at octahedral and tetrahedral lattice sites. The cation distribution is highly responsible for the peak position of octahedral and tetrahedral sites—the dielectric constant increases with frequency because of dipole, interfacial, and electronic/atomic polarization. AC conductivity is very low, reflecting that the material can be used as a dielectric medium in the microwave frequency range's L, S, and C bands. The best MAM among all prepared materials is Ba 1.5 Sr 0.5 Zn 2 Fe 27.72 Yb 0.28 O 46 which can be used for global positioning systems, weather radar, and satellite feeds as it has an excellent dielectric loss, remarkable tangential loss, and the reflection loss in P-, L-, S-, and C-bands. Other real-life application of all prepared materials are multi-layer chip inductor and longitudinal media recording. Flowchart: Step wise synthesis procedure. [Display omitted] [ABSTRACT FROM AUTHOR]

The Pechini method was used for the first time to synthesize the phase-pure nickel-containing cubic pyrochlore Bi 2 NiNb 2 O 9 (space group Fd-3m, a = 10.5371(5) Å), while the solid-phase reaction method provided no possibility to obtain impurities-free pyrochlore. At a synthesis temperature of 950°С, low-porosity ceramics with indistinct grain boundaries were formed. The results of elemental mapping indicated a uniform distribution of metal atoms on the surface of the sample. The X-ray energy dispersive analysis showed that the chemical composition of the synthesized sample corresponded to the predetermined theoretical composition. The calcination of the sample synthesized by the Pechini method was studied by the thermal analysis up to 1100°С. The functional composition of intermediate synthesis products was analyzed by vibrational spectroscopy (FTIR). In the FTIR spectrum of pyrochlore (4000–400 cm−1), absorption bands were identified at 829, 540, 654, and 490 cm−1. The dielectric properties of the pyrochlore were studied using an impedance spectroscopy. Pyrochlore Bi 2 NiNb 2 O 9 has the high relative dielectric permittivity of 145 and low dielectric losses of 0.001 (at 24°С, 1 MHz), which make it a promising for dielectric in multilayer ceramic capacitors. [ABSTRACT FROM AUTHOR]

As electronic devices strive for higher integration and faster signal transmission, the demand rises for polymer composites with high thermal conductivity (TC) and low dielectric constant (ε r). However, high TC composites often come with a high filler content, leading to a reduction in processibility and dielectric properties. Herein, by surface micro-welding strategy, we fabricated cohesive h-BN microspheres (SBO) with a quasi-hollow structure. The pre-constructed micro-nano network of h-BN inside the microsphere serves as a continuous pathway for heat transfer, while the internal space of the microsphere is divided into numerous gas chambers, establishing a foundation for low ε r. Benefiting from this structure, the TC of the prepared composite is 2.12 W/m·K, and its ε r is remarkably low at 3.24 (103 Hz), effectively balancing the TC and dielectric properties at a high filler loading. Furthermore, this designed structure significantly reduces the viscosity of the composite (measured 309 Pa s with a filler content of 50 wt% at 1s−1) due to the smooth surface of the microsphere. This strategy offers a facile approach for fabricating composites characterized by desirable TC, low ε r and excellent processibility, showcasing promising prospects for advancement in the realm of microelectronics. [ABSTRACT FROM AUTHOR]

The goal of this work is to produce nanocomposites films for energy-storing and optoelectronic applications by incorporating ceramic nanofiller into a polymer blend. By using the one-pot hydrothermal process, manganese ferrite nanoparticles (MnFe 2 O 4 NPs) have been created. The produced NPs' size and morphology were verified by TEM, and the findings show that the particles are shape spherical and average size particles of around 21.45 nm. Using the casting approach, a series of polymer nanocomposites (PNCs) comprising carboxymethyl cellulose (CMC) and polyethylene oxide (PEO) have been created with various contents of MnFe 2 O 4 NPs: 2.0, 5.0, 8.0, and 12.0 wt%. The XRD results, which display the changes in PNCs' microcrystalline properties, revealed a decline in the samples' degree of crystallinity. FTIR spectroscopy has been used to verify that PNCs are properly formed and that functional groups are present in the nanocomposites. Using a UV–Vis spectrophotometer, the optical properties were examined. The absorbance coefficient was calculated for each sample. As the nanoparticle content increased, so did the E g decreased both direct and indirect of the PNCs. An increase in MnFe 2 O 4 loading improved the thermal characteristics of the nanocomposites, indicating enhanced thermal stability of the films due to nanoparticle-to-CMC/PEO blend interaction. The adding of MnFe 2 O 4 nanoparticles to the CMC/PEO matrix enhances the charge conduction mechanism, as seen by the doped samples' noticeably improved conductivity findings. As frequency increased, the dielectric loss (ε ″) and dielectric constant (ε ′) values decreased. The produced sample (8 % MnFe 2 O 4 /CMC/PEO) is the best option for energy-storing and optoelectronic applications like supercapacitors and sensors due to the structural changes and improvements made to the optical, thermal, and dielectric properties. [ABSTRACT FROM AUTHOR]

The enhanced high-power performance of 0.93 Pb(Zr 1-x Ti x)O 3 -0.05 Pb(Mn 1/3 Sb 2/3)O 3 -0.02 Pb(Sc 1/2 Nb 1/2)O 3 (x = 0.48, 0.50, 0.52, 0.54, 0.56) piezoelectric ceramics (PZT-PMS-PSN) has been achieved with notable improvement in the piezoelectric coefficient (d 33). The presence of the monoclinic phase (C c) has led to an increase in d 33 from 214 pC N−1 to 315 pC N−1. Therefore, the composition 0.93 Pb(Zr 0.48 Ti 0.52)O 3 -0.05 Pb(Mn 1/3 Sb 2/3)O 3 -0.02 Pb(Sc 1/2 Nb 1/2)O 3 exhibits excellent mechanical and electrical parameters: a d 33 value of 315 pC N−1, a high mechanical quality factor of 1578, an electromechanical coupling factor k p of 52 %, and a low dielectric loss tanδ of only 0.288 %. Additionally, this ceramic exhibits a significantly high Curie temperature (T c), reaching up to 328 °C which stabilizes its ferroelectric phase. Moreover, the phase transition of PZT-PMS-PSN ceramics from rhombohedral to tetragonal phase was investigated by X-ray diffraction, Raman scattering, Piezo-response force microscopy. [ABSTRACT FROM AUTHOR]

SiC f /SiC composites provide a possibility to achieve the structure-function integration of military stealth materials used for aircraft tail. However, how to overcome narrow-band electromagnetic wave (EMW) absorption remains challenging. Herein, based on the adjustable permittivity of SiC fibers and the flexible design of woven structures, a gradient-structured SiC f /SiC hybrid woven metamaterial (GHWMM) is engineered with three different permittivity SiC fibers. The absorbing properties and mechanisms of the GHWMM were studied by combining experiment and simulation. Benefiting from the synergistic effect of strong dielectric loss, structural loss, and impedance matching, the GHWMM harvests an average reflection loss (RL) of −12 dB (93.7 % absorptivity), with an effective absorption bandwidth (EAB, RL ≤ −10 dB) of up to 10.7 GHz in the 4–18 GHz. Surprisingly, at high temperature of 1000 °C, the GHWMM still exhibits a RL below −5 dB in most frequency bands. Moreover, the GHWMM displays excellent wide-angle incidence characteristics, while possessing a remarkable flexural strength of 226.4 MPa. This work lays a foundation for the renewal of textile structures and the preparation of large-size assemblies, which holds promising prospect for application in the field of aircraft hot end components. [ABSTRACT FROM AUTHOR]

This study is about the qualitative description of the high dielectric constant (>103) and low dielectric loss in a two co-existing phases. According to earlier beliefs, a material with high dielectric constant will exhibit high dielectric loss. However, this study gives the opposite, where a material with high dielectric constant can exhibit low loss. Herein, we report on the effect of tetrahedral – octahedral interaction in a γ- Al 2 O 3 and CoAl 2 O 4 biphasic system. Phase identification was carried out using Synchrotron x-ray carrying a wavelength of 0.7 Å. The disorder caused by varying cobalt (Co) concentration results in a two co-existing phase system with varying local polarizability due to mixing of cations in a host matrix. In addition, a decreasing trend in the band gap energy has been observed for both the phases as a function of increasing Co concentration, which is attributed to the intra-gap localized density of states determined from the UV–Vis diffuse reflectance spectroscopy (DRS). [ABSTRACT FROM AUTHOR]

In this study, the thermal barrier material Yttria Stabilized Zirconia (YSZ) and the electromagnetic wave (EMW) absorbing agent samarium iron nitrogen (SmFeN) were used to prepare a YSZ/SmFeN/YSZ sandwich-structured composite. The YSZ/SmFeN interface was prepared perpendicular to the directions of EMWs. The EMW attenuation of the composites with different SmFeN contents and their mechanisms were studied using electromagnetic parameters, impedance matching, Cole–Cole circles, and minimum reflection loss (RL min value). Dielectric loss was the dominant mechanism behind EMW attenuation for the composites. In addition, the dipole orientation of SmFeN and the presence of phase interface induced the dielectric loss. The mechanism of dipole orientation polarization was influenced by SmFeN content; the lesser the SmFeN content in the composite, the higher the ε ′ (real part of dielectric coefficient). The frequency at which ε ′ peaked shifted decreased with increasing SmFeN content. Higher dielectric losses were observed in the frequency band of 4.0–8.0 GHz. The EMW absorption rate showed that the optimum EMW absorption effect was achieved when the thickness ratio of YSZ:SmFeN:YSZ was 1:4:1 and the thickness is 3.325 mm. The corresponding RL min was −35.3 dB and effective absorption bandwidth was 9.5 GHz (8.3–17.9 GHz). [ABSTRACT FROM AUTHOR]

In this study, nanocomposite films consisting of potato starch (PS), layered double hydroxide (LDH), and microcrystalline cellulose (MCC) were synthesized using the solution casting method. The MCC particles were used to stabilize the dispersion of LDH during film preparation. The study investigated the effect of LDH particles on the optical, electrical, dielectric, mechanical, and barrier properties of PS/MCC films. The X-ray diffraction and scanning electron microscopy analysis confirmed that the PS/MCC/LDH ternary films had a partially intercalated and partially exfoliated structure. FTIR and Raman spectroscopy analysis revealed the formation of new hydrogen bonds between PS hydroxyl groups and nanoparticles. The direct optical band gap decreased from 5.80 to 5.44 eV with increasing LDH content. The refractive index, optical conductivity and optical dielectric constant all improved with increasing LDH content. The presence of MCC and LDH had little effect on the optical clarity of the starch-based films. The improving of dielectric properties was demonstrated by decreasing the dielectric loss tangent with increasing LDH content. The addition of 1%, 3%, and 5% by weight of LDH to the pure starch PS film resulted in significant improvements in tensile strength and tensile modulus of the ternary nanocomposites. In addition, the water solubility of the nanocomposites decreased with the addition of LDH. The principal component analysis results confirmed the positive effect of higher biopolymer content on these properties. The results of the study confirm that PS/MCC/LDH nanocomposites films can be used in optical and electronic applications. [ABSTRACT FROM AUTHOR]

A CPW-fed, C-shaped antenna is designed for Ultra-wideband (UWB) applications. In the proposed design, there is a wide slot in the ground plane in such a way that the C-shaped radiator accommodates within that slot. Moreover, two slots have been cut on either side of the lower ground plane to down the return loss from 10 dB. The dimension of the antenna is 25 mm × 25 mm × 1.6 mm which is etched on the FR4 dielectric material having a loss tangent of 0.02 and a dielectric constant is 4.4. The bandwidth of the antenna is 9 GHz (3–12 GHz) or, 120%. The designed antenna can be used for broadcasting purposes because its E-fields radiation pattern is almost omnidirectional in a lower range of frequencies. Therefore, this designed antenna can be used in the upper-frequency band (3–6 GHz) of Wi-Fi communications. [ABSTRACT FROM AUTHOR]

The heating potential of microwave-heated bituminous mixtures depends on the heating characteristics of aggregates. This study focused on understanding the effect of mineral, chemical, and dielectric properties of aggregates on the rate of heating of aggregates, with special emphasis on the effect of the power level of microwave energy. Properties of the aggregates collected from 18 different sources were evaluated using X-ray diffraction, X-ray fluorescence spectroscopy, and a microwave vector network analyzer. Heating studies were conducted on the aggregates using a microwave oven at four different power levels (330, 525, 630, and 700 W). Thermal images, captured using a forward-looking infrared (FLIR) thermal camera, were used to obtain the heating characteristics, such as heating time, rate and nonuniformity of heating. The rate of heating of aggregates (0.212°C/s−1.007°C/s), nonuniformity of heating (0.059°C–0.218°C), and time of heating to 100°C (40–520 s) varied widely with the source of aggregate. In general, the heating rate and the degree of nonuniformity of the aggregates increased with increase in microwave power. Bulk mineralogy and chemical composition of aggregates significantly influenced the dielectric response of aggregates (adjusted R-squared values of 0.75 and 0.70, respectively) and the sensitivity of heating parameters to microwave power (adjusted R-squared values of 0.83 and 0.92, respectively). Two different predictive models were developed for estimation of heating rate of aggregates with (1) power, density, and dielectric loss factor, and (2) power, density, and aggregate chemical indices as independent variables. The adjusted R-squared values of these two predictive models were 0.84 and 0.92, respectively. [ABSTRACT FROM AUTHOR]

Lead‐based piezo‐ceramics like lead zirconate titanate (PZT) are a mainstay for many piezoelectric applications. However, lead oxide (PbO) evaporation during sintering poses a significant environmental challenge. Flash sintering (FS) is a novel technique that can densify ceramics in seconds and at a much lower furnace temperature. The liquid‐phase FS (LPFS) of PZT (Pb (Zr0.5Ti0.5) O3, with 3 wt.% Cu2O and PbO in the molar ratio of 1:4) is investigated in this work. Further, a comparison has been made among the lead loss, dielectric, and piezoelectric properties of flash‐sintered and conventionally liquid‐phase‐sintered PZT. It has been observed that the evaporation of PbO has been brought down 3–5 times by FS. The dielectric constant of LPFS PZT is significantly higher, especially at higher frequencies with lower dielectric loss. An enhanced piezoelectric coefficient in flash‐sintered PZT has also been observed. The LPFS of PZT shows that the lead loss can be brought down significantly with the added benefit of enhanced dielectric and piezoelectric properties. XRD and Rietveld analysis show an increase in tetragonality after FS in comparison with conventional sintering. XPS and ESR studies show a difference in defect concentration after FS in comparison with conventional sintering that is likely responsible for the enhanced dielectric and piezoelectric properties. [ABSTRACT FROM AUTHOR]

Ultra‐low temperature sintered ceramics, Li2(Mg1−xCax)2(MoO4)3 (x = 0.025–0.100), were synthesized using the solid‐phase method. XRD analysis revealed that adding Ca2+ increased the second‐phase CaMoO4 content. Particularly, Li2(Mg0.975Ca0.025)2(MoO4)3 ceramics exhibited excellent properties: εr = 9.31, Q × f = 55,400 GHz, and τf = −38.9 ppm/°C. Incorporating Ca2+ significantly improved the performance of ceramics. The microwave dielectric properties of Li2(Mg0.9Ca0.1)2(MoO4)3 ceramics sintered at 650°C showed enhancements: εr of 9.55, Q × f of 63,500 GHz, and τf of −10.8 ppm/°C. The rise in εr can be attributed to polarizability, while a higher packing fraction led to a larger Q × f value, and the reduced distortion of the [Li/Mg/CaO6] octahedra enhanced the τf value. Moreover, the increased of CaMoO4 also positively influenced the ceramic's properties. Furthermore, in accordance with the principles of complex chemical bonding, the elevation of ionicity, lattice energy, and bond energy of the Mo–O bond contributed to the enhancement of εr, Q × f, and τf, respectively. Raman spectroscopy showed a positive correlation between dielectric loss and full width at half maximum of the Raman peak. Good chemical compatibility between silver and Li2(Mg0.9Ca0.1)2(MoO4)3 ceramic was demonstrated through our co‐firing experiment. [ABSTRACT FROM AUTHOR]

(Pb,La)(Zr,Ti)O3 antiferroelectric (AFE) ceramics have attracted considerable interest due to their high‐energy storage density and numerous field‐induced phase transitions. However, the positional equilibrium of the A‐site and B‐site is typically maintained without considering that heterovalent doping of La3+ can induce defects within the material, leading to high‐temperature leakage conduction. In this work, we introduced the acceptor ion Na+ at the A‐site simultaneously and designed Pb0.9175–0.5xLa0.055NaxZr0.975Ti0.025O3 (x = 0.01, 0.03, 0.055, 0.07, 0.10) AFE ceramics. The dielectric properties of these ceramics exhibited a consistent pattern of improvement followed by deterioration as the content of Na+ increased. Notably, when x = 0.055 (Na5.5), the AFE ceramic demonstrated superior high‐temperature frequency stability with negligible leakage conduction. Impedance spectroscopy analysis suggested that Na5.5 displays the greatest resistance and highest Edc. Concurrently, the thermally stimulated depolarization current indicates that Na5.5 possesses the lowest defect concentration and the largest Ea. This can be attributed to the internal generation of defect dipole clusters (VPb′′−VO••−NaPb′−LaPb•$V_{{\mathrm{Pb}}}^{{\prime\prime}} - V_{\mathrm{O}}^{ \bullet \bullet } - {\mathrm{Na}}_{{\mathrm{Pb}}}^{\prime} - {\mathrm{La}}_{{\mathrm{Pb}}}^ \bullet $), which effectively restrict the movement of charged defects. These findings suggest that Na5.5 holds significant potential for application and offer insights into the understanding of internal defects in lead‐based AFE materials. [ABSTRACT FROM AUTHOR]

As a type of cellulose ether, cyanoethyl cellulose (CEC) is considered to be a promising candidate for polymer dielectrics due to its sustainable nature and high dielectric constant induced by the cyano groups. However, the relatively high conduction loss of CEC arising from the charge motion across the polymer degrades its dielectric properties. In this work, we designed and synthesized an all‐organic polymer composite of CEC/itaconic anhydride (ITA) to improve dielectric properties. The CEC matrix was graft functionalized by ITA via an esterification reaction between the anhydride groups of ITA and hydroxyl groups of CEC. Meanwhile, crosslinking structure was also established in the composite by the generation of diester. Significantly improved dielectric constant (εr), elevated breakdown strength (Eb), restrained dielectric loss (tan δ) and decreased conductivity (σ) were observed in the composites compared with unmodified CEC. The εr increased from 17 for pure CEC to 32 for CEC/ITA at 1 kHz, and Eb also soared from 145 MV m−1 for CEC to 226 MV m−1 for the composite. The tan δ reduced from 0.24 for pure CEC to about 0.05 for the composite at 100 Hz. This should be attributed to the molecule trapping centers arising from the high electron affinity ITA and the formation of crosslinked networks as well as hydrogen bonding, which impeded the electric conduction. It also provided additional advantages of better dielectric properties for the CEC/ITA composites than pure CEC at high temperatures, which may offer inspiration for the design and preparation of bio‐based dielectrics for high temperatures. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The influence of density and shape of hollow silicas (silica hollow tubes (SHT) or hollow glass microspheres (HGM)) on dielectric and heat‐resisting characteristics of poly(ether ketone ketone) (PEKK)/SHT and PEKK/HGM films was systematically investigated. The dielectric characteristics of PEKK/SHT or PEKK/HGM films decrease to a minimum, as their SHT or HGM contents approach 8 or 20 wt%, respectively, and the minimum dielectric constant (εr) and dielectric loss (tan δ) of PEKK/SHT or PEKK/HGM films decrease visibly with decreasing SHT densities. By filling with 0.46 g cm−3 mean density of SHT or HGM fillers, the minimum εr and tan δ of PEKK/SHT films are somewhat smaller than those of PEKK/HGM films. The linear coefficient of thermal expansion (LCTE) values of PEKK/SHT or PEKK/HGM films reduce and their onset degradation temperature values increase gradually with increasing SHT and HGM contents. Low εr/tan δ (2.11/0.0022 and 2.2/0.0027 at 1 MHz), LCTE (35.5 × 10−6 and 31.2 × 10−6 °C−1) and excellent heat‐resisting properties favorable for sixth generation (6G) ultrarapid communication are realized for appropriately prepared PEKK/SHT and PEKK/HGM substrate films. The free‐volume‐hole characteristics of PEKK/HGM or PEKK/SHT films approach a maximum as SHT or HGM contents reach an optimum value of 8 or 20 wt%, respectively. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Special multilayer heterostructures and lattice modulation play a crucial role in the field of microwave absorption. Herein, a unique “nested doll” MoS2/V2O3 heterostructures are synthesized via crystal epitaxy growth and solvothermal strategy. The synchronized modulation of lattice spacing and interfacial vacancies in MoS2 nanosheets is achieved by adjusting the S2⁻ concentration. A high concentration of S2⁻ expands the MoS2 lattice spacing and increases interfacial vacancies, facilitating the precise modulation of the orderly arrangement of MoS2‐V2O3‐MoS2 layers and inducing interfacial polarization. By increasing the number of V2O3‐MoS2 layers from two to five, a built‐in electric field is formed, which enhances charge transfer from the MoS2 surface to the V2O3 core. The introduction of vacancies reduces the MoS2 band gap, lowers the electron hopping barrier, increases dielectric loss, and ultimately synergistically improves microwave absorption (MA). As a result, the “nested doll” MoS2/V2O3‐5 (5 layers) microspheres exhibit superior MA behavior compared to other MoS2/V2O3 absorbers. The reflection loss reaches −69.65 dB and the effective absorption bandwidth achieves 7.68 GHz. These discoveries have contributed to the further development of multilayer heterostructures and improved advances in the theory of energy band structures and electromagnetic properties. [ABSTRACT FROM AUTHOR]

Herein, MgO–12 % TiO 2 (w) ceramics with different contents of Bi 2 O 3 –CuO sintering aid were prepared using a solid-state method. The effects of the sintering aid content on the sintering temperature and the dielectric and mechanical properties of the ceramics were studied. The material was characterized using scanning electron microscopy and X-ray diffraction and Precision LCR tester and universal testing machine and Archimedes drainage method. When the Bi 2 O 3 –CuO content was less than 9 wt%, the ceramic sample has higher dielectric properties. When the Bi 2 O 3 –CuO content was greater than 9 wt%, the dielectric properties will deteriorate. This is because Bi 2 O 3 participates in the chemical reaction between MgO and TiO 2 , forming a high dielectric loss Bi 4 Ti 3 O 7 phase. At high temperatures, Cu2+ can easily change valence to Cu+, promoting oxygen vacancies and increasing dielectric loss in ceramic samples. The introduction of Bi 2 O 3 –CuO produces new MgTiO 3 , Mg 2 TiO 4 , and Bi 4 Ti 3 O 12 phases in the sample structure, resulting in a structure in which the MgO grains in the sample are surrounded by the new phases that appear around them. This structure fills the pores, increases density, enhances mechanical properties. The dielectric properties of the ceramics were the when the sintering temperature was 1050 °C, and the Bi 2 O 3 –CuO content was 3 wt%. The dielectric constant and dielectric loss were 11.19 and 1.17 × 10−4, respectively. The bending strength of the ceramic sample increased from 138.72 MPa to 179.64 MPa when the Bi 2 O 3 –CuO content was increased from 3 wt% to 15 wt%. The Bi 2 O 3 –CuO sintering aid enables MgO to be better applied in ceramic substrates. [ABSTRACT FROM AUTHOR]

The impact of tin (Sn4+) doping on sodium yttrium copper titanate (Na 0.5 Y 0.5 Cu 3 Ti 4 O 12) ceramics, prepared using a conventional mixed-oxide route, was thoroughly investigated in terms of microstructure, dielectric properties, electrical response, non-linear behaviors, and humidity-sensing characteristics. All sintered ceramics showed a dense micro-structure and a pure Na 0.5 Y 0.5 Cu 3 Ti 4 O 12 phase without any secondary phases. The doped Na 0.5 Y 0.5 Cu 3 Ti 4−x Sn x O 12 ceramics, with x = 0.05, demonstrated excellent dielectric properties, including a low dielectric loss tangent (∼0.032) and a giant dielectric permittivity (∼1.8 × 104) across a wide temperature range. Sn4+ doping improved the non-linear behaviors at 25 °C in Na 0.5 Y 0.5 Cu 3 Ti 4 O 12 , with a reduced dielectric loss tangent corresponding to an enhanced grain boundary (GB) response. The colossal dielectric response is attributed to the internal barrier layer capacitor model, which relates to the Schottky barrier height (Φ B) at the GBs. Notably, the Φ B values for the Na 0.5 Y 0.5 Cu 3 Ti 4 O 12 ceramic increased with Sn4+ ion doping. Additionally, an in-depth study of the humidity-sensing properties of the Sn4+-doped Na 0.5 Y 0.5 Cu 3 Ti 4 O 12 material revealed that the capacitance at 1 kHz increased with increasing relative humidity levels, from 30 % to 90 %, suggesting potential applications in humidity-sensing technologies. [ABSTRACT FROM AUTHOR]

To reduce the dielectric loss of MXene/PVDF composites near the percolation threshold, a MnO 2 /MXene hybrid structure was successfully synthesized via an ultrasonic-assisted solution process, and MnO 2 /MXene/PVDF composite films were prepared by a solution casting method. The effects of different amounts of MnO 2 nanorods on the microstructure, thermal stability, dielectric properties and mechanical properties of the composite films were investigated. At 1 kHz, the dielectric constant of 7 wt% MnO 2 /MXene/PVDF is 37.3, and the dielectric loss is as low as 0.05. The electric modulus curve, Nyquist curve and equivalent analog circuit of the composites revealed strong interface polarization and microcapacitance effects in the composites. In addition, the composite films exhibit excellent mechanical properties, and the storage modulus of the composite film loaded with 10 wt% MnO 2 is 1990.5 MPa, which is 3.44 times that of pure PVDF. This study confirms that incorporating MnO 2 nanorods into MXene/PVDF composites is an effective approach for fabricating high-performance dielectric composites. [ABSTRACT FROM AUTHOR]

Strong absorption and large bandwidth are two contributors to material's electromagnetic wave absorbing performance. While spinel ferrite materials have garnered extensive attention in the realm of microwave absorption, their relatively low conductivity remains a practical challenge. In this work, NiCo 2-x Fe x O 4 (x = 0, 0.04, 0.06 and 0.08) precursor was prepared by hydrothermal and after-sintered method. It was found that Fe doping exhibit excellent EM absorption properties. Specially, when the Fe content is 0.08, the maximum reflection loss −48.90 dB at 15.40 GHz and the maximum effective bandwidth 4.20 GHz are achieved. More importantly, the absorption frequency can be broadened from Ku to C band even to S band with proper adjusting Fe content. Doping with Fe enhances conduction loss and make a significant contribution to dielectric loss, as a result, the impedance matching degree of the Fe-NiCo 2 O 4 composite is influenced by the synergistic effect of its dielectric and magnetic properties. This work provides a simple way for enhancing the microwave absorption capabilities of ferrite materials and provides insight into understanding conduction loss in microwave absorption. [ABSTRACT FROM AUTHOR]

The global focus on electromagnetic interference and pollution is undeniable. To counter these challenges, high-performance microwave-absorbing materials (MAMs), typically composed of dielectric and magnetic components, offer effective solutions by ensuring favorable impedance matching. Leveraging these MAMs has proven beneficial across various sectors, including 5G technology, information security, energy harvesting, diminished radar cross-section, and advancements in military applications. We successfully synthesized composites of La 1.5 Sr 0.5 NiO 4 (LSNO) and SrFe 12 O 19 (SrM) composites through ball milling and heat treatment. With the escalation of SrM weight percentage in the composites, noticeable alteration in structural, morphological, and static magnetic characteristics was ensured. Moreover, the amalgamation of these components bolstered the EM properties, consequently yielding exceptional microwave absorption capabilities in the composites. The composites with 40, 60, and 80 wt% of SrM (named S4, S6, and S8) exhibited excellent microwave absorption performance with an absorption rate of over 99.9 % for a thin thickness. The S4 and S8 composites attained reflection loss (RL) values of −34.75 dB and −36.93 dB, with 2.0 and 1.6 mm thicknesses, respectively. Meanwhile, the S6 composite achieved an RL value of −44.24 dB with a thickness of 1.9 mm. These composites' outstanding microwave absorption performance can be attributed to their significant magnetic loss, remarkable dielectric loss, and synergistic effects. [ABSTRACT FROM AUTHOR]

Vacancy engineering presents an appealing method for modifying the electronic structure of spinel architectures. However, based on well-defined vacancy concentrations, how to design anionic vacancies to modulate electromagnetic parameters as well as electromagnetic wave absorption (EMA) properties is less studied. Here, NiCo 2 Se 4 spinel structures were prepared using different selenization methods, and the Se vacancy defect concentration was controlled by changing the annealing temperature, thus regulating the EMA properties. Among them, the design of the hollow structure effectively enhanced the EMA performance. Moreover, the increase of Se vacancy concentration increases the conductivity loss while regulating the electronic structure, and also acts as an unsaturated site to induce the formation of dipoles to optimize the polarization loss. The effective absorption bandwidth (EAB) of NiCo 2 Se 4 -130 reaches 8.48 GHz at 2.4 mm at the highest Se vacancy concentration. This work establishes a direct relationship between vacancy concentration and the electromagnetic wave dissipation capability, offering valuable insights for the development of advanced EMA materials. [ABSTRACT FROM AUTHOR]

This study reports on the synthesis and electromagnetic wave-absorbing properties of Ag/Fe 3 O 4 /SiO 2 under various magnetic field intensities. The nanocomposites were prepared via a solvothermal method followed by a Stober proces, during which uniform magnetic fields were applied to induce the formation of one-dimensional nanochain structures. Results indicate that the Ag/Fe 3 O 4 /SiO 2 exhibit enhanced wave-absorbing capabilities under strong magnetic fields. Specifically, at a magnetic field of 600 mT, the composite achieves a minimum reflection loss value of −48.61 dB, accompanied by a broad effective absorption bandwidth. Furthermore, the microwave absorption performance of samples oriented horizontally along the circumference surface during preparation shows a significant improvement compared to non-oriented samples. It is attributed to the optimized electromagnetic wave transmission pathways and improved electrical conductivity and magnetic loss capabilities facilitated by the nanochain structures. Specifically, the nanochains effectively lengthen the wave propagation distance, promote charge migration, and intensify natural and exchange resonance effects. This research not only broadens the design paradigm for electromagnetic wave-absorbing materials but also offers novel strategies for their development. [ABSTRACT FROM AUTHOR]

EMI shielding reduces ambient electromagnetic (EM) radiation by reflecting and absorbing EM waves. Rapid technological growth has increased electronic gadgets and EM radiations, threatening the environment. Microwave materials with high absorption power and cheap cost are crucial for eliminating electromagnetic difficulties in stealth technologies. This study used a conventional solid-state reaction technique to prepare Bi 0.5 Na 0.5 TiO 3 (BNT) solid solutions and examined their structural, ferroelectric, dielectric, and shielding characteristics. This research describes an EMI shielding material that efficiently absorbs EM wave-induced radiation. Characterizations have been done to evaluate material behavior to support EMI shielding and confirm its absorbing nature. Field emission scanning electron microscopy (FESEM), Raman spectroscopy, and X-ray diffraction (XRD) were employed to examine the surface morphology, local lattice deformation with ionic configuration, and crystal structure. BNT exhibited a rhombohedral structure with R 3 c symmetry space group with crystallize size 81.5 nm and showed eight Raman active modes with an average grain size of 1.67 μm. The high dielectric constant, reduced dielectric tangent loss, and enhanced polarization value make BNT ceramic a good choice for electrical devices and microwave applications. BNT ceramics showed EMI shielding owing to absorption (SE T ∼ −23.65 dB, SE A ∼ −18.91 dB) at 9.2 GHz in the X-band (8.2–12.4 GHz). Meta-surface-based BNT absorbers were designed and simulated in the CST software. The peak depicted the absorption at 9.2 GHz with absorptivity of 91.56 %, 85.03 %, 84.36 %, and 64.6 % for designs 1, 2, 3, and 4, respectively. BNT ceramics have exceptional dielectric absorption properties, and dielectric and magnetic losses, which make them suitable for EMI shielding and absorption applications in the microwave region. [ABSTRACT FROM AUTHOR]

In this paper, the tape casting method was used to prepare BST (Barium Strontium Titanate) thin films and the effect of combining cold sintering and reaction sintering processes on the properties of BST sheets was explored. A comparison was made between cold sintering and direct BST sintering combined. The combined process yielded high-density BST sheets with significantly improved dielectric properties (the resulting BST sheets displayed a low dielectric loss of less than 0.02 with a dielectric constant of 720) at a reduced sintering temperature of 950 °C. The underlying mechanisms for this enhanced performance are explored through structural and sintering analysis. [ABSTRACT FROM AUTHOR]

SrTiO 3 ceramic samples were successfully prepared using an innovative approach that combined ion implantation technique with the reductive-reoxidation sintering method. SrTiO 3 ceramics were reductively sintered in N 2 and H 2 atmosphere, and Cu ion implanted, followed by thermal oxidation treatment in air. Experimental results demonstrate a notable reduction in dielectric loss while achieving a colossal permittivity (ε = 41,444 at 1 kHz, tanδ = 0.054 at 1 kHz). The phase structure, micromorphology, element valence state, dielectric properties and AC impedance spectrum characteristics of SrTiO 3 ceramic materials were studied, and the mechanism of dielectric properties was explained using the Internal Barrier Layer Capacitor (IBLC) effects. Research results show that Cu ion implantation, oxygen vacancies at ceramic grain boundaries, and oxygen adsorption during reoxidation thermal treatment play a key role in reducing the dielectric loss of the material. [ABSTRACT FROM AUTHOR]

Polymer-based ferroelectric composites, particularly those containing Poly (vinylidene fluoride) (PVDF), have emerged as preferred materials for flexible electronics and sensors owing to their excellent electro-mechanical attributes and ease of fabrication. The efficacy of PVDF composites is significantly influenced by the fillers and the proportion of the β-phase present. This research details the synthesis of La 0.7 Ba 0.3 MnO 3 (LBMO) particles via solid-state reaction, surface-functionalized with acetic acid, and subsequently introduced as nucleating agents into Poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) to fabricate LBMO/P(VDF-HFP) composite membranes. The LBMO fillers before modification significantly increased the β-phase content from 32.7 % to 87.8 % in 5 wt% unmodified LBMO/P(VDF-HFP) membranes. After modification, the hydroxyl groups attached to acetic acid-modified LBMO form hydrogen bonds with -CF 2 groups in P(VDF-HFP), inducing the formation of the β phase while enhancing macroscopic polarization and piezoelectricity. At a 7.5 wt% acetate-modified LBMO doping level, the composite membrane exhibits a β-phase content of 64.5 %, but concurrently enhancing the film's dielectric properties. At 103 Hz, the dielectric constant of 5 wt% modified LBMO/P(VDF-HFP) membrane increases to 24.8, with a minimal rise in dielectric loss from 0.0293 to 0.0314. Moreover, under a 10 N compressive load at 1 Hz, the 5 wt% modified LBMO/P(VDF-HFP) composite achieves an open-circuit voltage of 4.3 V. These improved dielectric and piezoelectric properties indicate the composite's suitability for energy harvesting applications. [ABSTRACT FROM AUTHOR]

Double perovskites have shown promise in the development of spin polarized conduction and ferromag semiconductors. In this category of double perovskite, we report on the lanthanum ferrocobaltite, co-doped with Pr and Mn. The polycrystalline ceramics were analysed for its structural properties by using Rietveld refinement of X-ray diffraction (XRD) and Raman spectroscopy measurements. The pristine and co-doped samples possess monoclinic structure with P2 1 /n space group. In the pristine compound Co and Fe octahedra are ordered periodically which later gets distorted upon cationic substitution. Scanning electron microscopy (SEM) and energy dispersive spectra (EDS) reveals the grain morphology and elemental analysis. The samples were investigated for their dc and ac electrical responses. The two-probe dc resistance was measured from room temperature RT to 575 K. Dielectric spectroscopy in the RT to 650 K temperature range was performed in the frequency range of 50 kHz to 5 MHz. We observed that introducing Pr at La-site and Mn at Fe site creates structural disorder and tilt in octahedra which results in decreasing the dielectric constant at RT but increases significantly at higher temperature with low dielectric loss. ac conductivity was found to increase with increasing temperature indicating the thermally governed hopping mechanism. All these features validate their potential applications as a high temperature capacitor and can be widely used in automotive and aerospace domains for the storage device application. [ABSTRACT FROM AUTHOR]

BaIn 2 O 4 ceramics with the monoclinic crystal system of the P 2 1 / c space group were synthesized using a solid-state reaction method. The sample sintered at 1250 °C exhibits a relative density (94.3 %) and the following microwave dielectric properties: ε r = 16.3, Q × f = 49,500 GHz, τ f = −73.1 ppm/°C. The bond valence results shows that the deviation of permittivity (24.9 %) between the experimental (ε r = 16.3) and calculated values (ε r C-M = 13.05) obtained using the Clausius−Mosotti equation may be ascribed to the rattling effect of Ba2+ and In3+. Compared with orthorhombic CaIn 2 O 4 and SrIn 2 O 4 ceramics, BaIn 2 O 4 ceramics have lower Q × f values possibly because of the intrinsic loss caused by nonharmonic lattice vibration. The E dc value (0.43 eV) of BaIn 2 O 4 demonstrates that the defects are caused by the single ionized oxygen vacancies. The intrinsic ε r (14.7) and Q × f (105,600 GHz) values of the BaIn 2 O 4 ceramic was inferred through infrared reflectivity spectroscopy. All results demonstrate that the dielectric properties are affected not only by density, ionic polarizability, and rattling effect of cations, but also by the crystal system, and particularly the intrinsic factors. [ABSTRACT FROM AUTHOR]

TiO 2 -based colossal dielectric ceramics have emerged as a prominent research focus in recent years. However, their further applications have been constrained by several key limitations, including the requirement of high sintering temperature (>1400 °C), relatively high dielectric loss (>0.05, 1 kHz), and temperature stability (<200 °C). This study reports rutile (In 0.5 Ta 0.5) 0.1 Ti 0.87 O 1.88 F 0.12 ceramics at 1220 °C sintering using 12 % InF 3 as the acceptor In3+ source, which exhibits a colossal dielectric constant (1.1 × 105) and an ultra-low dielectric loss (0.0071) at 1 kHz and room temperature, even loss values below 0.04 (20 Hz - 100 kHz). Notably, the thermal stabilities (10 kHz, 100 kHz) simultaneously satisfy X9E (Δε r /ε 25 °C ≤ ±4.7 %) above 300 °C. F − not only supplies electrons to enhance the semiconductivity of grains, but also decreases the oxygen vacancy and average grain size (270 ± 12.53 nm) to improve grain boundaries resistances, which reduces dielectric loss and enhances frequency and temperature stabilities. As a result, the dielectric mechanism is mainly related to internal barrier layer capacitor (IBLC) and high grain boundary resistance. Therefore, this strategy provides a creative design for developing TiO 2 -based ceramics. [ABSTRACT FROM AUTHOR]

The lead metaniobate (PbNb 2 O 6 , PN) with high Curie temperature is widely used to fabricate transducer for high-temperature application up to 300 °C. However, evident dielectric anomalies and direct-current resistivity degradation were experimentally observed in PN-based ceramics at high temperature, which may significantly restrict the working temperature range for well logging application. When the sample was heat-treated at 260 °C for 3 h in silicon oil, the dc-resistivity of ceramics at 260 °C decreased from 3.8 × 108 to 1.0×107 Ω⋅cm, accompanied by 43 times increase in tan δ at 1 kHz. To investigate the cause of these phenomena, the in-situ piezoelectric, dielectric properties and dc-resistivity were systematically investigated in the samples subjected to heat-treatment at 260 °C in silicon oil. It is revealed that the porous structure of PN-based ceramics allows for the infiltration of silicon oil as a minor phase, and the accumulation of its decomposers within the pores would exert significant influence on the dielectric property and dc-resistivity of ceramics at elevated temperatures. However, the samples still demonstrate excellent thermal stability in piezoelectric property, with value of k t maintaining 0.39 at 260 °C in oil. In addition, the low Q m is not the intrinsic property of PN ceramics, but rather related to the phase transition of silicon oil within pores of ceramics, as indicated by the increase in Q m from 47 to 80 after heat-treatment in air. [ABSTRACT FROM AUTHOR]

ZnO linear resistors, due to its excellent performance, are widely used in numerous industries and gradually replacing traditional conductive resistors, presenting a broad prospect for application. To study the effects of lanthanide oxides on the microstructure and electrical properties of ZnO-based linear resistors, this paper prepared Dy 2 O 3 -doped ZnO-Al 2 O 3 -TiO 2 -NiO based linear resistors using a solid-state sintering method. The results showed that proper doping of Dy 2 O 3 could inhibit the growth of ZnO grains, leading to more uniform grain growth. Additionally, doped with appropriate amount of Dy 2 O 3 could enhance the linear performance of ZnO linear resistors, reduce the grain boundary barrier height (φ b), and decrease dielectric loss. Linear resistors with nonlinearity coefficient (α) of 1.07, grain boundary barrier height (φ b) of 0.0934 eV and resistance-temperature coefficient (α T) of −5.39 × 10−3/°C were obtained. The doping of Dy 2 O 3 could improve the comprehensive performance of ZnO linear resistors, making the fabricated ZnO linear resistors are more suitable for working in high frequency electric fields. The study and analysis of Dy 2 O 3 doped ZnO linear resistors are of significant importance for the preparation of high performance ZnO linear resistors. [ABSTRACT FROM AUTHOR]

The advancement of military technology, 5G communication, and electronic equipment has increased the demand for efficient electromagnetic wave absorption materials. Calcium manganate (CaMnO 3) is a commonly used dielectric absorber due to its excellent dielectric polarization effect. However, traditional ceramic materials like CaMnO 3 have low conductivity, making it difficult to achieve impedance matching and electromagnetic loss simultaneously. In this work, to address this issue and create ideal wave-absorbing materials, one-dimensional La-doped CaMnO 3 materials were synthesized using a simple biological template hydrothermal method. By studying the relationship between doping content and electromagnetic parameters, it was found that the La-doped CaMnO 3 material exhibited excellent electromagnetic wave absorption properties, with a minimum reflection loss (RLmin) of −73.62 dB and a maximum effective absorption bandwidth of 3.3 GHz in the X-band. The introduction of La elements, which have different electronegativities from Ca ions, altered the electron cloud distribution in the sample, leading to the formation of electric dipoles that disrupt charge distribution and dissipate electromagnetic waves. The dielectric loss in fibrous La-doped CaMnO 3 is mainly due to interfacial polarization. The fibrous structure allows for increased contact area with the air medium, while the porous structure introduces air bubbles that alter the dielectric properties between the sample and the air medium. This not only enhances impedance characteristics to some extent but also triggers interfacial polarization. Both of these factors help improve the material's ability to absorb electromagnetic waves. The successful creation of this one-dimensional absorbing material opens up possibilities for developing new one-dimensional absorbing materials using a straightforward method. [ABSTRACT FROM AUTHOR]

In this paper, Ce 2 [Zr 1− x (Cd 1/3 Sb 2/3) x ] 3 (MoO 4) 9 (CZ 1− x (CS) x M, x = 0.01–0.1) were prepared via the conventional solid-state method. XRD and Rietveld refinement analyses confirmed the formation of a single-phase CZ 1− x (CS) x M solid solution with a space group of R -3c(167). The sintering behavior of the samples were investigated using SEM and relative density, which showed that optimal densification for CZ 0.98 (CS) 0.02 M ceramics were achieved at 675 °C with an average grain size of 1.70 μm. The P-V-L theory revealed the significant influence of the Zr(Cd/Sb)-O bond on the dielectric properties of CZ 1− x (CS) x M ceramics. Furthermore, far-IR reflectance spectra indicated that the measured dielectric loss value (1.04 × 10−4) is in line with the calculated value (1.60 × 10−4), suggesting a substantial impact of phonon oscillation absorption on the dielectric properties. Notably, CZ 0.98 (CS) 0.02 M ceramics demonstrated superior performance at 675 °C, with ε r = 10.44, Q × f = 93,152 GHz (at 12.96 GHz), and τ f = −17.73 ppm/°C. [ABSTRACT FROM AUTHOR]

In this study, SiC/SiCN composites with BN interphase were prepared using chemical vapor infiltration (CVI) and polymer infiltration and pyrolysis (PIP) methods. The evolution and related mechanisms of mechanical and microwave absorption properties of the composites after oxidation at 800 °C, 1000 °C, 1200 °C, and 1400 °C were investigated. The results showed that with the elevating of oxidation temperature, the flexural strength of SiC/SiCN composites gradually decreased, with a retention rate of 56.7 % after oxidation at 1400 °C. The main reasons for the deterioration of mechanical properties were the changes in the crystal structure of SiC fibers under high-temperature conditions and the formation of brittle SiO 2 phases on the surface and interior of the SiCN matrix. With the increase in oxidation temperature, the microwave absorption performance of the composites showed an enhancing trend. The main reasons were that after oxidation treatment, the reduction of free carbon content and the formation of SiO 2 film layers from the oxidation of SiC and SiCN led to a decrease in the complex permittivity of the composites, resulting in better impedance matching and dielectric loss capabilities. The contributions of BN interphase to stress dispersion, interface polarization, and oxidation protection significantly enhance the mechanical and electromagnetic absorption properties of the composites. Therefore, SiC/SiCN composites are high-temperature structural microwave absorbing materials with great application prospects. [ABSTRACT FROM AUTHOR]