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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]

Undoped and Al-doped CsLiB 6 O 10 (CLBO) crystals have been grown by top-seeded solution growth (TSSG) method using Cs 2 O–Li 2 O–MoO 3 flux system. The thermophysical properties of undoped and Al-doped CLBO were systematically studied, including thermal expansion, specific heat, thermal diffusion and thermal conductivity. The measured thermal expansion coefficients of undoped and Al-doped CLBO in the temperature range of 30–500 °C are α a = 1.81 × 10−5/°C, α c = −2.98 × 10−5/°C and α a = 1.10 × 10−5/°C, α c = −2.56 × 10−5/°C, respectively, displaying much weaker anisotropy than those of widely used nonlinear optical crystals, such as β-BaB 2 O 4 and CsB 3 O 5. CLBO exhibits specific heat of 0.86–1.03 Jg−1K−1 in the temperature range from 30 to 500 °C. The thermal conductivities of undoped and Al-doped CLBO at 30 °C are respectively calculated to be κ a = 1.73 Wm−1K−1, κ c = 1.69 Wm−1K−1 and κ a = 1.74 Wm−1K−1, κ c = 1.49 Wm−1K−1, which are larger than those of β-BaB 2 O 4. Dielectric properties were investigated in the temperature range of 20–400 °C within the frequency range of 100 Hz–1 MHz. The measured dielectric constants of undoped and Al-doped CLBO at 1 MHz and 25 °C are ε a = 5.27, ε c = 5.92 and ε a = 4.96, ε c = 5.49, respectively. Additionally, undoped and Al-doped CLBO exhibit significantly low dielectric losses (0.005–0.016 at 1 MHz and 25 °C) and superior dielectric temperature stability (20–300 °C). These results indicate that undoped and Al-doped CLBO possess excellent thermophysical performance and could be two promising dielectric material candidates for high frequency device applications. [ABSTRACT FROM AUTHOR]

The CaCu 3 Ti 4 O 12 and CaCu 2.95 Zn 0.05 Ti 4- x Cr x O 12 (x = 0, 0.05, and 0.10) ceramics were synthesized via solid-state reaction and sintered at 1110 °C for 3 h. XRD analysis confirmed that all samples maintained a single phase, free from impurities. SEM images revealed minor differences in grain size when comparing the undoped ceramic to those with co-doping. Notably, the co-doped CaCu 2.95 Zn 0.05 Ti 3.95 Cr 0.05 O 12 ceramic exhibited significantly enhanced dielectric properties, including a high dielectric permittivity of 4.17 × 104 and a low loss tangent of 0.027. This ceramic also demonstrated stable dielectric permittivity with less than a 22 % variation from −60 to 90 °C, meeting the X5S and Y5S ceramic capacitor standards. In our first-principles calculations, we selected the CaCu 2.95 Zn 0.05 Ti 3.95 Cr 0.05 O 12 structure because of its superior dielectric characteristics compared to the others. Our total energy calculations revealed that the Cr and Zn dopants are likely to be far apart from each other, indicating the absence of defects caused by the Zn and Cr dopants in the grains of our samples. The electrical property results indicate that the substitution of Zn2+ and Cr3+ ions into the CCTO lattice may help reduce oxygen loss during the sintering process at high temperatures. As a result, the need for charge compensation of Cu and Ti ions is diminished, leading to an increase in the grain and grain boundary resistances in the CaCu 2.95 Zn 0.05 Ti 3.95 Cr 0.05 O 12 ceramic. Based on these results, the electrical conductivity of the material decreases, which contributes to a lower loss tangent value and improved temperature stability of the dielectric permittivity. The experimental and computational results indicated that the high dielectric permittivity is primarily due to the formation of an internal barrier layer capacitor, while improvements in dielectric properties may be associated with changes in intrinsic defects, which enhance the grain boundary response. [ABSTRACT FROM AUTHOR]

Remarkable dielectric properties and enhanced hardness were achieved in high-entropy TiO 2 -based ceramics in this work by incorporating multiple pairs of donor-acceptor (D-A) cations (D = Nb5+, A = In3+, Al3+, Fe3+, Ga3+, La3+). The introduction of high-entropy engineering may facilitate the creation of favorable and stable microstructural features as lattice distorted and localized defect cluster, thereby enhancing the dielectric performance, thermal stability and mechanic properties. The composition of [Nb 0.5 (In 0.2 Al 0.2 Fe 0.2 Ga 0.2 La 0.2) 0.5 ] 0.01 Ti 0.99 O 2 exhibits remarkably colossal permittivity (ε r) value of approximately 18488 and low dielectric loss (tanδ) value of around 0.014 at 1 kHz. Furthermore, the thermal stability of the dielectric permittivity for [Nb 0.5 (In 0.2 Al 0.2 Fe 0.2 Ga 0.2 La 0.2) 0.5 ] 0.01 Ti 0.99 O 2 ceramic meets the X9D standard, and the dielectric loss stays below ∼ 0.05 in the temperature range from −55 to 150 °C. Besides, the Vickers-hardness of [Nb 0.5 (In 0.2 Al 0.2 Fe 0.2 Ga 0.2 La 0.2) 0.5 ] 0.01 Ti 0.99 O 2 gets increased by over 37 % as compared to that of (Nb5+, In3+) co-doped ceramic (INTO). We presented in this work the influence of high-entropy on the dielectric and mechanic properties of TiO 2 -based ceramics, offering valuable insight into future development of colossal dielectric ceramics. [ABSTRACT FROM AUTHOR]

The poor dielectric properties of epoxy resins limit their application in microelectronics, and active ester curing agent is an effective means to enhance the dielectric properties of epoxy resins. However, the phenyl active ester curing resins nowadays have the problem of low mechanical properties. In this work, a novel naphthalene‐based active ester‐cured resveratrol epoxy resin system (REP/NDA) was prepared for the first time. Compared with the phenyl‐active ester‐cured epoxy resin (REP/PDA), the naphthyl‐active ester prepared epoxy resin has obvious advantages in mechanical properties. The experimental results indicated a tensile strength measurement for REP/NDA at 91.9 MPa, the tensile strength of REP/PDA was 65.3 MPa, and the tensile strength of REP/NDA was 141% of that of REP/PDA. The prepared REP/NDA epoxy resin exhibits favorable dielectric properties, evidenced by a dielectric constant of 3.02 at 10 MHz and a dielectric loss of 0.0042, very good thermal stability (T5% of 379°C), excellent water absorption (only 0.49% for 7 days from 2 to 8°C) and good dimensional stability (coefficient of thermal expansion below Tg of 77 ppm). The first synthesis of naphthalene‐based active ester curing agent offers a reference for creating new low dielectric epoxy resin materials that work out exceptionally. [ABSTRACT FROM AUTHOR]

As communication technology continues to evolve, 5G technology is becoming more mature, and 6G technology is steadily advancing. Microwave equipment is moving toward high frequency, miniaturization, low loss and high temperature stability, and microwave dielectric ceramics have been deeply applied in this field. To elevate the Q × f value of CoNb2O6 system, Ta5+ was introduced into CoNb2O6, and CoNb2‐xTaxO6 (0.0 ≤ x ≤ 0.8) ceramics were prepared by the traditional solid‐phase method. By X‐ray diffraction, it was observed that at x = 0.8, in addition to a single niobium ferrite phase, information of tantalate phase also appeared. Raman spectral detection and group theory analysis indicate that Ag(2) and Ag(3) modes are the dominant Raman vibrations at ≈873 cm−1. Furthermore, the polarization rate affects the εr value, and the bond energy of Nb/Ta‐O and the recovery force characterized by the average deformation of the [Nb/TaO6] octahedron are the key elements influencing the temperature coefficient of the resonance frequency (τf). The internal strain, ordered induced size, and chemical bonding valence of ionic valence states are the key factors that can increase the Q × f value. Moreover, the introduction of ions with lower electronegativity leads to an enhanced electronic compensation of oxygen vacancies, which also reduces the dielectric loss. This paper enriches the theory related to low dielectric loss and shows that CoNb1.8Ta0.2O6 (εr = 21.4832, Q × f = 100723 GHz, τf = ‐61.38 ppm/°C) ceramics with superior microwave dielectric properties are expected to be used in wireless communication devices. [ABSTRACT FROM AUTHOR]

Bismuth layer‐structured ferroelectrics (BLSF) show great potential as piezoelectric materials for high‐temperature applications. In this study, c‐axis/[001]‐textured CaBi4Ti4O15 (CBT) ceramic was synthesized through templated grain growth (TGG) method. A high Lotgering factor (f) of 96% was achieved in textured CBT ceramic using 20 wt% CBT homogeneous template. The piezoelectric coefficient d33 has significantly increased from 7.8 pC/N for random ceramic to 24.3 pC/N for textured ceramic (poled perpendicular to the c‐axis/[001] texture direction), representing an impressive 300% enhancement while maintaining an ultra‐high Curie temperature (TC) of 788°C. In addition, a low dielectric loss (tanδ = 0.4%) and relatively high resistivity (ρ = 1.1 × 1012 Ω·cm) were achieved simultaneously at room temperature. The significant enhancement of d33 in textured CBT ceramic origins from its strong piezoelectric anisotropy. The large d33,T⊥ is due to the nature of polarization switching in CBT (the spontaneous polarization PS of CBT is along a‐axis direction, and the switching of PS is restricted within the a–b plane). Furthermore, the variation of d33,T⊥ remained below 10% across the temperature range of 25–700°C, highlighting the excellent thermal stability of the textured CBT ceramics. These findings suggest that textured CBT ceramic is a promising piezoelectric material for high‐temperature sensor applications. [ABSTRACT FROM AUTHOR]

In this study, a series of Ba4Li(Nb1‐xVx)3O12 (x = 0.05∼0.3) ceramics were synthesized using the solid‐state reaction method. X‐ray powder diffraction (XRD) analysis shows that the composite ceramics contain both Ba4LiNb3O12 and Ba3(VO4)2 phases, without any other phases present. The grains consist of Ba4LiNb3O12 and Ba3(VO4)2, as illustrated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Additionally, with the increase of V content, the grain size decreases, and the εr${{\varepsilon }_r}$ (microwave dielectric constant) decreases, the τf$\tau {{\ }_f}$ (resonant frequency temperature coefficient) value decreases, and the Q×f$Q \times f$ value increases (where Q$Q$ = quality factor = 1 / dielectric loss, and f$f$ = resonant frequency). The densest Ba4Li(Nb0.7V0.3)3O12, with a εr${{\varepsilon }_r}$ of 31.3, τf$\tau {{\ }_f}$ of + 70 ppm/°C, and high Q×f$Q \times f$ of 42 850 GHz, was obtained at a sintering temperature of 1350°C. Furthermore, the addition of 5 wt.% BaCu(B2O5) (BCB) into Ba4Li(Nb0.7V0.3)3O12 resulted in obtaining dense ceramics at a sintering temperature of 925°C, with a εr${{\varepsilon }_r}$ of 23.5, a high Q×f$Q \times f$ value of 14 370 GHz, and τf$\tau {{\ }_f}$ of + 88 ppm/°C. Further investigations have shown that Ba4Li(Nb1‐xVx)3O12 ceramics are chemically compatible with Ag, suggesting its potential use in low‐temperature cofired ceramics technology. [ABSTRACT FROM AUTHOR]

We synthesized ZnFe2O4 and CoFe2O4 nanoparticles and investigated their magnetic and electromagnetic behaviors at room temperature. X-ray diffraction analyses indicated that these materials having average crystallite sizes of 22–31 nm, and their crystal structure belongs to the cubic-spinel class. While ZnFe2O4 exhibits soft magnetic behavior, with Ms = 88 emu/g and Hc = 130 Oe, CoFe2O4 exhibits hard magnetic behavior, with Ms = 65 emu/g and Hc = 620 Oe. Investigations into the complex permittivity and permeability dependent on the frequency (f) and thickness (t) revealed remarkable changes in their values at frequencies f = 12–16 GHz for both samples. In the range f = 13.5–13.8 GHz, reflection loss magnitudes of devices based on ZnFe2O4– and CoFe2O4– with t = 2.25–2.75 mm were about 11.3–14.2 dB, corresponding to electromagnetic wave absorption of 90–95%. Considering loss tangents, we found that both dielectric and magnetic losses contributed to the electromagnetic dissipation in the investigated materials. [ABSTRACT FROM AUTHOR]

A broadband microwave composite metamaterial absorber based on the Debye model, consisting of triple dielectric loss layers and different-ordered metallic fractal pattern vertical layers, has been proposed. The research results show that when all the three dielectric layers are silicon carbide fiber (SiCf), the composite absorber presents two intense absorption bands with a bandwidth of 5.44 GHz. The length (l) of the metallic pattern and thickness (t) of the top dielectric layer can effectively regulate the reflection loss performance. Additionally, the effective absorption bandwidth increases to 13.44 GHz when the relative absorption bandwidth reaches about 119.15% by replacing SiCf at the top dielectric layer with the dielectric loss materials which satisfy the Debye model. The research results show that the absorption bandwidth obviously increases with dielectric loss materials of distinct Imε. Furthermore, the proposed fractal pattern shows robustness to the variation of complex permittivity spectrum, expanding the range of suitable dielectric materials for composite broadband metamaterial absorbers. [ABSTRACT FROM AUTHOR]

This paper presents the effect of sintering temperature on the structural, electrical, and dielectric properties of polycrystalline Dy0.4Sm0.6FeO3 orthoferrite prepared via the sol–gel method, and sintered at 800°C, 1000°C, and 1200°C. Rietveld refinement of XRD confirmed that the samples sintered at 800°C and 1000°C exhibit a single phase, whereas the sample sintered at 1200°C shows a small amount of Dy3Fe5O12 impurity. Room temperature Raman spectra confirmed the active vibrational modes of Dy0.4Sm0.6FeO3 and the impurity phase. FESEM images illustrate an increase in grain size with increasing sintering temperature and sintering at 1000°C shows less porosity. P-E loop data reveal the deficient ferroelectric and leaky nature of the samples. The dielectric constant and dielectric loss increase with increasing sintering temperature, and the dielectric relaxation phenomena is shifted to the high temperature side with increasing sintering temperature. The dielectric loss and activation energy are lower for the sample sintered at 1000°C compared to the other samples. The findings of this paper establish that the sample sintered at 1000°C, Dy0.4Sm0.6FeO3 , optimizes the structural, electrical, and dielectric properties. Dy0.4Sm0.6FeO3 sample prepared through the sol–gel method and sintered at 800°C, 1000°C, and 1200°C, investigated for their structural, electrical, and dielectric properties. DSFO samples sintered at 800°C and 1000°C exhibit a single phase without any impurity. [ABSTRACT FROM AUTHOR]

In this work, dense CdCu3(Al 1 ∕ 2 Ta 1 ∕ 2 ) x Ti 4 − x O 1 2 ceramics were prepared by a conventional solid phase method. The effect of Al 3 + /Ta 5 + dopants on the dielectric properties of CdCu3Ti4O 1 2 ceramics was systematically investigated. Upon Al 3 + /Ta 5 + co-doping, the dielectric properties of CdCu3(Al 1 ∕ 2 Ta 1 ∕ 2 ) x Ti 4 − x O 1 2 were significantly enhanced. Particularly, the CdCu3(Al 1 ∕ 2 Ta 1 ∕ 2 ) 0. 0 5 Ti 3. 9 5 O 1 2 material displays a decent dielectric property, where dielectric constants ( ε r ∼ 2 7 1 8 1), loss tangent (tan δ ∼ 0. 0 6 9) at a test frequency of 1 kHz are able to satisfy the application temperature requirement of the Y6R capacitor. Surprisingly, the refined grains resulting from Al 3 + /Ta 5 + co-doping lead to heightened resistance at grain boundaries, which is closely associated with enhanced dielectric properties. Meanwhile, the giant dielectric property of the materials can be attributed to the effect of the internal barrier layer capacitance. The obtained results are expected to provide a new idea for obtaining high dielectric constant and low loss tangent in CdCTO-based materials and promote the practical application of such materials. [ABSTRACT FROM AUTHOR]

Silicone rubber (SR) rubber is manufactured more efficiently in the modern age by using multiwalled carbon nanotubes (MWCNTs); this makes silicone rubber suitable for a wide range of industrial applications. In this paper, it has been elaborated the fabrication of SR/MWCNTs nanocomposites that is improved dielectric behaviours under thermal stability. Then, the dielectric properties of SR/MWCNT nanocomposites were investigated in order to understand MWCNT’s potential as a piezoelectric sensor. The electric modulus, dielectric constant and dielectric loss of SR/MWCNT nanocomposites have been studied at a variety of frequencies (up to 100 kHz) and temperatures (up to 40°C). A comparative study has been analysed the dielectric behaviours between SR and SR/MWCNTs nanocomposites under variant mechanical deformation samples (virgin and compressed). Physical and dielectric characteristics of nanocomposites were dramatically improved as the multiwalled carbon nanotubes loading was add and better than pure blend films. The nanocomposites films had good physical applications, suggesting that they could be a viable alternative to piezoelectric sensors. As a final point, it has been demonstrated that there is an effectively controlled in dielectric parameters of silicone rubber by using multiwalled carbon nanotubes (MWC-NTs) within the existing mechanical forces on the long life time for piezoelectric sensors applications. [ABSTRACT FROM AUTHOR]

In this work, the structure, dielectric and optical properties of PVDF/zirconia-based polymer nanocomposites were investigated. The morphology and structure of the nanocomposites were analyzed by XRD, SEM, FT-IR, UV and EDS analyses. It was determined that the forbidden gap for the PVDF/1%ZrO2-based nanocomposite is 4.7 eV, for PVDF/5%ZrO2-4.5 eV, and for PVDF/10%ZrO2-4.2 eV. It is shown that the dielectric permittivity of the nanocomposites increases sharply up to 3% of ZrO2 nanoparticles in the polymer and then decreases slightly with an increase in the concentration of nanoparticles. An increase in the permittivity indicates an increase in polarization processes in nanocomposites at a 3% conentration of ZrO2 nanoparticles in the PVDF matrix. It has been established that the dielectric loss tangent at low frequencies starts to decrease, and at high frequencies, it increases. The increase in the dielectric loss tangent at high frequencies is explained by an increase in relaxation processes and energy dissipation in these systems. [ABSTRACT FROM AUTHOR]

Borosilicate glass substrates are widely used in packaging utilizing through-glass-via (TGV) technology. In this study, we prepared glass substrate samples with different Al 2 O 3 contents while considering the mixed alkali effects, summation factors, and Dell–Bray model. We then used Raman spectroscopy to analyze the structural changes in the glass network and investigate the thermal expansion and dielectric properties. The thermal expansion coefficients were in the range of 8.17–8.79 × 10−6/°C, and the dielectric losses were in the range of 0.009–0.022 (at 1 GHz). The Raman spectroscopy results showed that the [AlO 4 ] structural units enhanced the network connectivity and limited ion migration; these effects were beneficial for reducing the dielectric loss but limited the improvement of the thermal expansion coefficient. The addition of more than 4 wt% Al 2 O 3 and reduction of the [AlO 4 ] units led to a decrease in the dielectric loss (0.022@1 GHz) and an increase in the coefficient of thermal expansion to 8.53 × 10−6/°C. Differential scanning calorimeter test results indicated that the glass substrate could be used in high-temperature environments. Finally, 55 μm vias were completed using the TGV technique. Overall, this study explored an idea for preparing glass with a high coefficient of expansion and low dielectric loss to address the thermal mismatch and high dielectric loss in electronic packaging systems. [ABSTRACT FROM AUTHOR]

Iron-based alumina (FeAl x O y) nanocomposites are microwave-absorbers and catalysts, which makes them promising for emerging microwave-assisted thermocatalytic technologies. Solution combustion synthesis (SCS) has been used to synthesize FeAl x O y powders, and prior work has demonstrated that adjusting SCS parameters significantly changes phase composition and specific surface area of the products. However, it is unclear how synthesis parameters affect their microwave-absorbing properties, which are essential for optimizing microwave-assisted technologies. To address this challenge, in the present work, twelve different FeAl x O y products were synthesized at different combinations of the SCS parameters such as two fuels (citric acid and glycine), two heating modes (hotplate and muffle furnace), and three Fe:Al molar ratios (2:1, 1:1, 1:2). Dielectric and magnetic properties of the products were characterized using a network analyzer and a vibrating sample magnetometer. Based on the measured permittivity and permeability, penetration depth and reflection loss were calculated as a function of frequency and bed thickness. The products were heated by microwaves at 2.45 GHz and then examined with X-ray diffraction (XRD) analysis. For all products, the magnetic saturation was lower than for bulk iron oxides because of the small crystallite size and aluminum substitution. The use of glycine induced high dielectric losses and enabled fast microwave-heating rates compared to citric acid. Higher Fe:Al ratio also led to higher dielectric and magnetic losses. With glycine fuel, SCS in a furnace induced larger penetration depth and lower microwave absorption than SCS on a hotplate. The minimization of reflected power was more sensitive to the thickness of the product bed than to the frequency of the electromagnetic field. Post-heating XRD analysis revealed different phase transformations in the FeAl x O y powders depending on the SCS parameters. An FeAl x O y material, synthesized via incipient wetness impregnation, lacked magnetic losses and did not heat well as compared to the SCS products. [ABSTRACT FROM AUTHOR]