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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]

In the quest for advanced composite materials with exceptional dielectric properties, in this work we investigated the preparation and performance of triphasic (NiFe2O4–2LaFeO3)–Ni–poly(vinylidene fluoride) (PVDF) cermet–polymer percolative composites. Utilizing a solution-casting technique for composite film formation, the research focuses on enhancing dielectric performance through the incorporation of electroceramic (NiFe2O4–2LaFeO3:NFO–2LFO), metallic nickel (Ni) fillers and magnetic field-assisted solidification. These composite films comprising a triphasic blend of magnetic electroceramic and metallic filler within a PVDF polymer matrix exhibited an intricate interplay between magnetic domains, crystalline phases, and polymer matrices. Applying a weak magnetic field during solidification facilitates the alignment of magnetic domains, leading to a 33% improvement in dielectric performance. Morphological analysis revealed homogeneous microstructures and well-defined interfaces. Through experimental measurements and percolation theory approximations, it is demonstrated that when the Ni content is close to the percolation threshold (fc), the dielectric constant due to space charge polarization of the composite with a 0.35 volume fraction of NFO–2LFO and a 0.18 volume fraction of Ni reached up to 595 with a low dielectric loss. These results highlight the critical role of interfacial polarization and magnetic field-induced alignment in enhancing the dielectric properties. The high magnetic responsiveness allows the fillers to magnetically aligned orientations within the PVDF polymer leading to significant gain in the performance. [ABSTRACT FROM AUTHOR]

Despite the excellent properties of ceramic materials for electronic devices, this study systematically investigates the significant effects of strontium (Sr2⁺) substitution on the structural, morphological, electrical, and dielectric behavior of Ca 2-x Sr x MgSi 2 O 7 (x = 0, 0.2, 0.4, 0.6) ceramics. The composite was prepared via a solid-state route and characterized using techniques such as FESEM-EDAX, BET, XRD, Hall Effect measurements, and an LCR meter, respectively. The surface morphology of the structure was initiated to be smooth, compact, dense, island-shaped and porous. It is noted that the grain size reduced (from 1.10 μm to 0.72 μm) while the surface area enlarged (from 90 m2/g to 122 m2/g) with Sr substitution. XRD study showed that all the ceramics samples, after sintering at 1250 °C for 5 h. Higher amount of Sr, enhanced the crystallinity, as validated by the peak intensification. Correspondingly, the electrical resistivity and dielectric permittivity of Ca 2-x Sr x MgSi 2 O 7 was decreased with Sr substitution. Particularly, the Ca 1.6 Sr 0.4 MgSi 2 O 7 unveiled the lowermost electrical resistivity (76 Ω cm) and dielectric permittivity (εr = 848) but the uppermost dielectric loss (tan δ = 1.06) at 1 kHz. The attained outcomes exhibited the appropriateness of these samples for use in capacitor and antennas design. [ABSTRACT FROM AUTHOR]

Herein, the fused silica ceramics integrating good mechanical and dielectric properties were successfully prepared by gelcasting and pressureless sintering by introducing ZrO 2 as reinforcement phase. After sintering at 1250 °C for 6 h, the introduced m-ZrO 2 underwent a displacive phase transformation from m-ZrO 2 to t-ZrO 2. More importantly, some t-ZrO 2 phases were stably retained to room temperature by doping Y 2 O 3. The ZrO 2 phases filled the irregular pores formed by micro-scale fused silica particles, which significantly increased the bulk density from 1.56 g/cm3 for pure fused silica ceramics to 2.07 g/cm3 for fused silica ceramics containing 20 wt% ZrO 2. By reason of the increasing bulk density, stress-induced phase transformation toughening, microcrack toughening, and dispersion strengthening, the fused silica ceramics containing 16 wt% ZrO 2 displayed the highest flexural strength of 110.6 MPa, which was 83.4 % higher than pure fused silica ceramics. Throughout X-band, the prepared fused silica ceramics with different ZrO 2 contents showed good dielectric properties. The dielectric constant and dielectric loss tangent were less than 4.0 and 0.01, respectively. This work demonstrates that combining gelcasting and pressureless sintering is a practical approach for fabricating fused silica ceramics possessing good mechanical and dielectric performance through introducing ZrO 2 as reinforcement phase. [ABSTRACT FROM AUTHOR]

The phase engineering of the polarization interface is of great significance in modifying dielectric loss in electromagnetic wave (EMW) attenuation process, but hard to conduct in a complex hybrid system. Herein, a twin‐phase of β/γ‐MoCx@CN with matched Fermi level and closed work function properties in lightweight MoCx nanoflower is constructed, facilitating electron transport withdraw enhanced conductivity and polarization. Moreover, the EMW multiple dissipations among the β/γ‐MoCx@CN polarization interface is promoted, displaying better matched impedance. It delivered a remarkable minimum reflection loss (RLmin) of −74.2 dB at the thickness of 1.5 mm, which far beyond the single phased β‐MoCx@CN, γ‐MoCx@CN and reported MoCx‐based EMW absorbers. The radar cross‐section (RCS) map of β/γ‐MoCx@CN is simulated, showing a brilliant maximum reduction value of 13.6 dB m2 at the theta angle of 30°. This work presented an excellent sample of atomic‐level manipulation of interfacial polarization in dielectric MoCx EMW absorption materials. [ABSTRACT FROM AUTHOR]

Selenide-based functional composites materials demonstrated tunable dielectric properties and heterogeneous interface design, which has been widely studied in electromagnetic (EM) wave absorption field. Herein, Metal-organic frameworks (MOFs) derived carbon coating copper selenide (Cu 2-X Se@C) composites were successfully fabricated by using the Cu-MOFs as precursor. After reacting with the gaseous Se in the selenization annealing process, the metal host was converted into the Cu 2-X Se nanoparticles, where embodied in the carbon matrix transformed from the organic linker. Based on the tunning dielectric property and building heterogeneous interface, MOFs-derived Cu 2-X Se@C composites displayed outstanding EM wave absorption performance. Though the conduction loss, interfacial and dipole polarization behaviors, the minimum reflection loss (RL min) value of Cu 2-X Se@C-600 composites reached to −74.3 dB at 11.7 GHz when the thickness is 2.0 mm. The efficient absorption bandwidth (EAB) can be regulated via controlling the applied thickness. When the thickness is 2.3 mm, above-mentioned Cu 2-X Se@C-600 got the broadest absorption performance with the EAB of 5.5 GHz from the 7.7–13.2 GHz, covering the whole X-band. Therefore, MOFs-derived selenide-based composites shed a new design strategy for constructing broadband EM wave absorption, especially in radar stealth applications. [ABSTRACT FROM AUTHOR]

Cr-substituted Ni 2 U hexaferrite series (Ba 4 Ni 2 Fe 36-x Cr x O 60 for x = 0.0 to x = 2.0 with a step size of 0.5) was prepared via sol-gel auto-combustion route and annealed at 1200 °C for 6 h. The samples were investigated using XRD, FTIR, SEM, XPS, and high frequency (1 MHz–6 GHz) dielectric and microwave absorption measurements (VNA). XRD studies revealed that Cr3+ ions successfully substituted in BaNi 2 U-type hexaferrite and have a single-phase structure. The average crystallite size decreased while the percentage of porosity increased with the substitution. FTIR spectra confirmed the formation of the hexaferrite phase in all compositions. SEM micrographs revealed that the prepared samples are hexagonal. XPS spectra show the presence of all constituent elements in the samples. The dielectric constant, dielectric loss, and A.C. conductivity of samples was analyzed. Cole-Cole plots with single semicircles of different radii show the grain and grain boundaries affecting the conduction process. Moreover, Cr-substitution enhanced the microwave absorption capability. The hexaferrite sample Ba 4 Ni 2 Fe 35 Cr 1.0 O 60 , with a pellet thickness of 1.81 mm, showed the highest M.W. absorption at 1.09 GHz frequency with a reflection loss (R.L.) value of −55 dB. The hexagonal-shaped morphology, high porosity, and enhanced reflection loss value suggest their use in high-frequency microwave applications. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) pollution frequently disrupts the regular operation of sophisticated electrical devices, necessitating the urgent development of lightweight EM wave absorbers that possess powerful absorption capability. Herein, we report a simple method for the preparation of Fe and heteroatom co-doped biochar composites (FeX-BC, where X = N, S) by directly carbonizing the precursors of anhydrous FeCl 3 , cherry kernel powder, and heteroatom dopants (melamine or Na 2 S 2 O 3 ·5H 2 O). By adding different amounts of dopants during the synthesis of the precursors, it is possible to adjust the heteroatom content of the FeX-BC samples with precision. It is worth mentioning that the FeN 0.1 -BC composite delivers the best EM wave absorption performance with an effective absorption bandwidth of 4.8 GHz and a minimal reflection loss of −63.2 dB. Furthermore, the significant attenuation of EM wave can be attributed to the synergistic interplay of magnetic loss, dielectric loss and the enhanced impedance matching. This study introduces a simple methodology for the fabrication of EM wave absorbers, a significant contribution to the synthesis, advancement, and functional applications of biomass-derived materials. [ABSTRACT FROM AUTHOR]

The traditional approach to designing ferroelectrics through phase boundaries has limitations in regulating polarization configuration and achieving significant performance enhancements. In contrast, the concept of high-entropy materials has emerged as a promising strategy for designing new materials with enhanced properties. Herein, by incorporating the high configurational entropy (S config) strategy, the investigation explored the influence of S config on the electrical properties of PNN-PHT piezoceramics. The results demonstrated that high S config values were highly beneficial in improving the piezoelectric properties and significantly influenced the microstructure and grain size. The increase in S config value was found to be positively correlated with the Rayleigh coefficient (α), dielectric loss (tan δ), and frequency dispersion (γ), while inversely correlated with the coercive electric field (E c). By exploring the mechanism via Raman and simulation analyses, it was discovered that high S config induces enhanced disorder, increased lattice distortion, and sharp volume changes. This ultimately resulted in a richer phase structure, reducing the potential energy barriers and leading to a lower activation energy (E a) required for polarization switching. This finding provides novel strategies and directions for the development of high-voltage and high-coercive-field materials, holding promise for designing piezoelectric devices with enhanced power density and precision. [ABSTRACT FROM AUTHOR]

This study examined the morphological, structural, electrical, and dielectric characteristics of hard-soft (H-S) Sr 0.5 Ba 0.5 Sn x Fe 12-x O 19 /CoFe 2 O 4 (x ≤ 0.10) ferrite nanocomposites (NCs), created using one-pot sol-gel combustion route. This study systematically investigated the electrical/dielectric features of H-S Sr 0.5 Ba 0.5 Sn x Fe 12-x O 19 /CoFe 2 O 4 NCs where x is within the range of 0.00 ≤ x ≤ 0.10. The examination realizes frequencies that reach 3.0 MHz, conducted within 20 °C–120 °C. A detailed analysis was performed to investigate various conduction mechanisms linked with dielectric constant, dissipation factor, AC/DC conductivity, loss of dielectric capacity, and real/imaginary modulus, which were explored across the entire range of Sn ion substitution ratios. Observations reveal that the conductivity variations adhere to power law dynamics concerning frequency, predominantly influenced by the Sn ion substitution ratios within the NCs. Furthermore, the frequency dependency of the dielectric coefficient across all NCs substantiates the common propagation of dielectric behavior, prominently contingent upon the substitution ratio of "x". Notably, the majority of dielectric parameters observed in H-S Sr 0.5 Ba 0.5 Sn x Fe 12-x O 19 /CoFe 2 O 4 (x ≤ 0.10) NCs are attributable to grain-to-grain boundaries, elucidated by conduction mechanisms similar to those observed in most compositional ferrites, explicable through Koop's model. [ABSTRACT FROM AUTHOR]

Herein, microwave dielectric ceramics of the Ba 4 Sm 9.33 Ti 18 O 54 ceramics are substituted at A sites by partially replacing Sm at A1 sites with Ce, and the effects of ionic substitution at A sites on ceramic crystal structure and microwave dielectric properties are investigated. The Ba 4 (Sm 1-x Ce x) 9.33 Ti 18 O 54 (BSCT) ceramics prepared through the solid phase method has a typical tungsten–bronze structure, and its lattice spacing increases gradually with the increase in Ce content x. This increase is reflected in the increase in the cell volume and growth of ceramic grains. However, the excess Ce after Ce content exceeds 0.25 leads to the growth of ceramic grains and increase in porosity between grains, which in turn increases the dielectric loss of the ceramic. Under optimal sintering conditions, the ceramic crystal has a maximum atomic packing density of x = 0.25, which corresponds to its most stable structural properties, and the highest Q × f value of 9013 GHz. Raman spectroscopy results indicate that in titanium oxygen octahedrons, an increase in Ce substitution can effectively weaken the bending and tensile vibration intensities of titanium oxygen bonds, further enhancing structural strength. [ABSTRACT FROM AUTHOR]

A paste was developed using commercially available BaTiO 3 nanoparticles and subsequently used to fabricate 5 cm × 5 cm freestanding films via a simple screen-printing method. The dielectric properties of the resultant freestanding films were investigated using sintering temperature as a parameter. The results showed that the desired bulk behavior could not be attained in films sintered at 900 °C. When the sintering temperature was increased to 1000 °C and 1100 °C, the films exhibited bulk and single-crystal-like behaviors; sintering at 1200 °C resulted in a film with dielectric properties superior to those of bulk and single-crystalline BaTiO 3. In addition, the dielectric loss was less than 0.04 in the temperature range from room temperature to 160 °C, indicating that the film is a highly practical freestanding film. The newly developed technology for forming freestanding films with thicknesses ranging from tens to hundreds of micrometers can be used to develop not only materials for multilayered ceramic capacitors but also materials for piezoelectric transducers, actuators, positive-temperature-coefficient thermistors, and ultrasonic devices. [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, alumina was selected as the second phase reinforced fused quartz ceramics and SiO2–Al2O3 composite ceramics were fabricated via digital light processing (DLP) 3D‐printing. The effect of the sintering procedure on the mechanical and dielectric properties of SiO2–Al2O3 composite ceramics were investigated in detail. The results show that the amount of cristobalite precipitation is the key factor affecting the properties of composite ceramics. The amount of cristobalite precipitation in composite ceramics could be controlled effectively by adjusting the heating rate, holding time, and sintering temperature. The sintering procedure is set as the heating rate of 4°C/min, sintering temperature of 1200°C, and holding time for 2 h, the flexural strength of SiO2–Al2O3 composite ceramic is 47.13 MPa, dielectric constant ranges from 2.90 to 2.97, and the tangent of loss angle is less than 0.041. SiO2–Al2O3 composite ceramics with high flexural strength and low dielectric constant were obtained by sintering procedure screening and optimization. [ABSTRACT FROM AUTHOR]

Reversible cross‐linked structures are widely used to turn thermoset plastics into recyclable and self‐healing vitrimer materials, but seldom applied in traditional flexible rubber/ceramic composites. In this paper, dioxaborolanes based flexible poly (isoprene (IP)‐co‐acrylonitrile (AN)) vitrimer is synthesized as the rubber matrix by copolymerizing with functional monomers at 5°C for 7 h, and mixed with 5 wt% modified barium titanates (BT) to prepare flexible high dielectric vitrimer composite. The materials are characterized by FTIR, TGA, SEM, DMA, etc. The results indicate that reversible crosslinking can occur above 76.4°C, and copolymerizing with the dioxaborolanes based monomers can turn poly (IP‐co‐AN) into the flexible vitrimer. The poly (IP‐co‐AN)/BT vitrimer composite not only shows a good thermal stability below 145.6°C, but also exhibits an excellent particle dispersivity and a certain self‐healing function at 80°C. The poly (IP‐co‐AN)/BT vitrimer composite has a storage modulus E' about 3.18 MPa at 25°C and Tg about −5.4°C, and shows a higher relative permittivity about 7.5 and lower dielectric loss about 0.156 at 1 k Hz. The results indicate that this paper provides a new method to achieve multifunction and high dielectricity for composites. Highlight: Reversible cross‐linked structures are applied in rubber / ceramic compositesCross‐linked flexible composites are reprocessable and self‐healingReversible bonds between particles and matrix improve compatibilitySynergism of BaTiO3 and cross‐linked structure enhances dielectric properties [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]

The mineral, Burckhardtite, Pb2TeFe[AlSi3O8]O6, is synthesized and characterized. A new analogue, Pb2TeGa[AlSi3O8]O6, is successfully prepared for the first time under laboratory conditions. The substitution of Ga3+ by Ti0.5M0.5 (M=Co2+, Ni2+) results in new compounds with the Burckhardtite mineral structure. The transition metal‐containing compounds exhibit interesting new colors, partly resulting from d‐d transitions and metal‐to‐metal charge transfer (MMCT) transition. The Ga compound shows a deep UV cut‐off (~86 %), which is one of the better known values of deep UV cut‐off compounds. The compounds exhibit good dielectric behavior with low dielectric loss. The Eu3+ ‐ substituted samples show deep red emission with a long lifetime of ~0.89 ms. The magnetic behavior of the transition metal containing compounds indicates anti‐ferromagnetic interactions. The successful synthesis of the naturally occurring mineral along with newer analogues with interesting properties suggests that it is profitable to investigate compounds of mineral origin. [ABSTRACT FROM AUTHOR]

In this work, Yb-doped Sr0.95Ba0.05Bi2Ta2O9 powders were synthesized by the citric acid-assisted method. The prepared powders were uniaxially pressed and sintered at different temperatures. Structure, morphology, and dielectric properties were investigated. The use of either a 1200 °C sintering temperature or motifs for a reduction tanδ purpose. The results showed that Yb has not caused a significant change in dielectric properties at low temperatures, thus indicating its ability to reduce dielectric loss smoothly. At high temperatures, the introduction of ytterbium elements could reduce both Curie temperature and conductivity. According to Jonscher's universal power law, the correlated barrier-hopping (CBH) model describes the AC conductivity mechanism. However, the non-overlapping small polaron tunneling (NSPT) model may be used to show that this is only possible at a specific temperature. The Arrhenius law and the CBH module provide estimates of the various energy barriers that space charges should overcome; however, these barriers get higher as the dopant concentration rises. [ABSTRACT FROM AUTHOR]

High‐performance microwave absorption (MA) materials are attracting growing attention to solve the expanded electromagnetic interference problems. Herein, zeolitic imidazolate organic frameworks (MOF)‐67 (ZIF‐67) are grown in situ on the sheet of graphene oxide (GO) through the coordination of Co2+ with oxygen functional groups. Through carbonization in an inert atmosphere, Co@carbon polyhedra (Co@CP)‐decorated reduced GO composites (Co@CP‐rGO) with a large number of heterogeneous interfaces are successfully obtained. The composites demonstrate excellent MA performance. With a filler loading of 10 wt%, the optimal minimum reflection loss (RL) of the composite can reach −54.6 dB. More importantly, the composites with thickness of 3.5 and 2.5 mm show the effective absorption bandwidth (RL < −10 dB) of 4.75 GHz (8.18–12.93 GHz) and 6.56 GHz (11.44–18 GHz), fully covering the X‐ and Ku‐band. It is proposed that the synergistic effect of multiple dielectric loss, magnetic loss, reflections and scattering contributes to the high MA performance. [ABSTRACT FROM AUTHOR]

Valeramide and halogenated phenol in solvent benzene have been studied using DFT. Dielectric relaxation studies have also been undertaken. The wave functional characteristics like reduced density gradient (RDG), electron localization function (ELF), localized orbital locator (LOL) are also evaluated. It has been found that the computed FMO energies accurately depict the characteristics of electron excitation which provide an explanation for the charge transfer. MEP analysis is done to identify electrophilic and nucleophilic sites. The theoretical analysis of the UV-Visible spectrum using the TD-DFT method in solution and the computational investigation of spectroscopic wavenumbers was also carried out (IR, Raman). Thermodynamic properties of title compound at different temperatures was carried out. Various dielectric parameters, like the dielectric constant ε ′ , the dielectric loss ε ″ at microwave frequency, the static dielectric constant ε0 and the dielectric constant ε∞ at optical frequency, were measured across five distinct molar ratios (i.e. 1:3, 1:2, 1:1, 2:1 and 3:1). While the relaxation time τ2 for group rotation is utilized to identify the steric interaction of the proton donor, Higasi's single-frequency equation is proven to measure multiple relaxation time τ1 to determine the intensity of hydrogen bonding. At a 1:1 (molar ratio), the values of relaxation time were found to be high. Molecular docking was done in a supplementary effort to support intermolecular interactions. [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]

With the development of communications technology, the copper‐clad laminate (CCL) for integrated circuits (IC) pointed to the direction of high‐frequency and high‐speed development, that is, a lower dielectric constant and dielectric loss requirements. Bismaleimide (BMI) resins feature stable dielectric properties and excellent thermal stability over a wide temperature range, widely used in the manufacture of high‐frequency and high‐speed CCL substrates. However, the comprehensive performance of BMI resin itself, including dielectric properties, still cannot fully meet the needs of the ever‐changing communications industry, so the molecular design modification of BMI resin to enhance the dielectric properties is currently one of the key research directions for integrated circuit CCL. This paper reviews the development of BMI resins and their applications, focusing on the main methods of molecular design modification and formulation optimization, including allyl, diamine, internal chain‐extended, and chemical/physical blending modification. Finally, the low dielectric BMI resin and its application and development in high‐frequency and high‐speed CCL are summarized and prospected. Future research directions include the design and synthesis of multi‐component copolymers to further realize the balance between low dielectric and comprehensive performance, as well as exploring the possibility of novel composite modifications to provide more competitive high‐performance materials for the IC laminate field. Highlights: The development of bismaleimide resin and their applications are reviewed.Bismaleimide monomers' synthesis and chemical reaction are summarized.The modified methods of bismaleimide resin in low dielectric are reviewed.Future research directions of low dielectric bismaleimide are prospected. [ABSTRACT FROM AUTHOR]

Barium titanate is a ferroelectric material used as a dielectric in thin film capacitors owing to its high dielectric constant. Barrier layers are utilized in these capacitors to improve the capacitors' performance by controlling the microstructure and creating thin resistive films. In this paper, the effect of barrier layers in Pt/BT/Pt capacitors is studied using zinc oxide and aluminium oxide. The performance parameters such as capacitance density, leakage current, equivalent series resistance, dielectric loss and dielectric strength of Pt/BT/Pt thin film capacitors with barrier layers of different sizes are simulated using COMSOL Multiphysics modeling software. 2 nm thick aluminum oxide as Pt ‐ BT barrier layer gives optimal performance. The leakage current, dielectric loss, capacitance density, equivalent series resistance and dielectric strength of Pt/BT/Pt capacitor are found to be 0.519 mA, 9.62×10−12, 172.8 fF/μm2, 9.62 kΩ, 108 V/m respectively whereas that of Pt/ALO/BT/ALO/Pt capacitor are found to be 1.56×10−18 A, 7.81×10−18, 11.6 fF/μm2, 9.01×1015 Ω, 5.05×109 V/m respectively. The low capacitance in Pt/ALO/BT/ALO/Pt capacitor is due to the low dielectric constant of aluminium dioxide barrier layer. The reduced leakage current and increased equivalent series resistance is due to the low conductivity of the aluminium oxide barrier layer. The use of aluminium oxide barrier layer between the conductive surfaces can reduce the electric field and increase the breakdown voltage, leading to improved dielectric strength and reduced dielectric loss. [ABSTRACT FROM AUTHOR]

2-D transition metal-chalcogenides (TMCs) are lucrative as frequency selective absorbers (FSAs) because of strong electronic polarization and enhanced dielectric loss. In the present work we have developed inks made of 2-D TMCs such as NiSe2, CoSe2 and used them to develop metastructures having high reflection loss. The structures have conductivity peaks depending on concentration of the 2D structure in the paint. It is observed that the absorption bandwidth and frequency seem to depend on the composition of 2D TMC along with the structures made. This provides an additional method to modulate the properties of FSA. [ABSTRACT FROM AUTHOR]