Low Loss Tangent Research Articles

Effects of boron nitride nanoplates on the dielectric and mechanical properties of carbon nanotubes/silicone rubber composites

AbstractCarbon nanotubes (CNTs) have aroused great attentions in silicone rubber (SR) composites due to the excellent electrical and mechanical properties. However, the distribution of CNTs is not ideal because of the agglomeration effect of nanomaterials. Incorporating different dimensional nanofillers may be a solution. In this work, two‐dimensional boron nitride (BN) was added to fabricate CNTs/BN/SR composites. The results showed that BN could benefit the dispersion of CNTs and improve the dielectric and mechanical behaviors of the composites. Large dielectric constant (5.35, 92% more than pure SR) with extremely low loss tangent (0.00108) was obtained in the SR composites incorporated with 2 wt% CNTs and 5 wt% BN. High tensile stress (836 kPa) and elongation at break (332%) were also achieved, with a low elastic modulus of 557 kPa. Besides, the CNTs/BN/SR composites had thermal stability up to 400°C. Thus, enhanced dielectric and mechanical properties were achieved in CNTs/BN/SR composites by incorporating different dimensional nanofillers, which have great potential applications in dielectric elastomer composites.

Role of mixed oxidant and controlled oxygen partial pressure heat treatment to regulate the dielectric properties and resistivity of SrTiO3-based CP ceramics

Sr0.99La0.01TiO3 (SLT10) colossal permittivity (CP) ceramic materials were synthesized using solid phase method and secondary heat treated using mixed oxidant 35%Bi2O3–10%Al2O3–20%MgO–25%CuO–10%SiO2 oxidant. The heat treatment atmospheres were chosen as O2, air, and Ar to correspond to different oxygen partial pressures. The dielectric properties of the Sr0.99La0.01TiO3-Percolated (SLT10-P) ceramics were investigated, and the contribution of the oxidant to the resistivity enhancement was verified by complex impedance spectroscopy and DC resistivity tests. Excellent dielectric properties were obtained for SLT10-P Air ceramic sample (16543 for dielectric permittivity and 0.016 for loss tangent), and the resistivity was increased from 2.13 × 108 Ω cm (SLT10) to 1.23 × 1011 Ω cm (SLT10-P Air). The resistance degradation mechanism of SLT10-P ceramics and oxygen vacancy migration in the process of resistance degradation were studied by using resistance monitoring device and thermally stimulated depolarization currents (TSDC) test. The introduction of oxidant optimizes the temperature stability and resistivity of SLT10 ceramics, but it will lead to the decrease of dielectric permittivity. The atmosphere of heat treatment changed the concentration of oxygen vacancy in ceramics. When SLT10-P O2 was treated in O2 atmosphere, the concentration of oxygen vacancy in ceramics decreased, which led to the decrease of dielectric permittivity and the increase of grain boundary resistance. For SLT10-P Ar ceramic, more oxygen vacancies and free electrons are induced by low oxygen partial pressure heat treatment, which enhances the dipole effect of electron pinning defects and leads to colossal dielectric permittivity, but high concentration of oxygen vacancies will affect the resistance decline. In SLT10-P Air ceramic, the coexistence of colossal permittivity and low loss tangent and high resistance is realized.

Enhancing future technologies: Sol-Gel synthesis of Sr0.6Ag0.4MnO3 manganite perovskite

The research successfully produced Sr0.6Ag0.4MnO3, a silver strontium manganite with the desired perovskite crystal structure, using the sol-gel technique. Extensive analysis revealed its notable characteristics, indicating potential uses across various fields. X-ray diffraction showed the compound's tetragonal structure at room temperature, affirming its stability. Morphological and chemical assessments confirmed the material's consistency and evenness, with crystallites averaging 27 nm (from XRD) and 90 nm (from SEM). The material displayed a ferro-paramagnetic transition at 375 K, suggesting suitability for magnetic applications, alongside a slight drop in electrical resistance under a magnetic field, hinting at potential magnetoresistive properties for electronic devices. In terms of dielectric properties, particularly at low frequencies, the material demonstrated a high dielectric constant and low tangent loss, indicating its potential for electrical components. Overall, these findings position Sr0.6Ag0.4MnO3 as a versatile material with promising applications in magnetism, electronics, and electrical components.

Thermal characterization of ceramic pills at millimeter waves with a TE01δ cavity resonator

The progress in 5G/6G technology prompts a demand for new materials operating at millimeter waves that can be exploited as substrates for electronic devices or antennas. In particular, a rapid development of millimeter wave band communication technology demands ceramic materials, which could be applied in low temperature cofired ceramic (LTCC) techniques. This kind of ceramics should possess a low dielectric constant (εr), a low loss tangent (tanδ) and a near-zero temperature coefficient. In the view of above, there is an urgent need for accurate and reliable material microwave characterization techniques that can operate at frequencies well above 15 GHz. Due to the fact that the majority of LTCC ceramic materials can be produced in a cylindrical shape, a suitable characterization method exploits a cylindrical resonator operating at a TE01δ mode, which is dedicated to the characterization of low-loss materials also as a function of temperature.

Negative Dielectric Constant in Novel Structure of PA-GO Composite /MnO2/Fe3O4/n-Si

This manuscript presents a novel structure of PA-GO composite with MnO2/Fe3O4/n-Si. This assembly was arranged by simple technique. It was examined by scanning electron microscope (SEM), X-ray diffraction (XRD) and Raman spectroscopy (RS). The novelty here is that the negative dielectric constant appeared for all considered voltages at the spot point frequencies 1000, 100 and 10 Hz, in spite of all literature proved that the dielectric constant has negative values only at higher frequencies (almost above 1 MHz). Also, the dielectric loss is negative at the higher frequencies at all considered voltages and temperatures. This structure has low dielectric loss tangent (tan δ ranging between 4 to 50) for all investigated voltages and temperatures and also has high rectification ratio reach to 1200 times, and high Rj. The electrical properties of this structure were examined by conventional/dlnI, Nord and Cheung method.

Temperature-dependent dielectric response of free standing PVDF-MoS2 nanocomposite films

Poly(vinylidene fluoride) (PVDF) and its copolymers are known for possessing the highest electroactive response including dielectric constant, piezoelectric and ferroelectric effects which has a wide range of applications such as in energy transfer, energy generation and storage, monitoring and control, and include the development of capacitors, sensors, actuators and so on. We report an enhancement in dielectric properties in PVDF generated by the addition of MoS2 nanosheets. The addition of 1 wt% MoS2 nanosheets as a filler in PVDF, stabilize its beta phase over the alpha phase, resulting in a significant increase in dielectric constant (ε’) across a wide range of frequencies (100 Hz to 1 MHz) and temperatures (140 K- 340 K). The high dielectric constant was achieved by the PVDF-MoS2 nanocomposite while maintaining a relatively low tangent loss factor of 0.94. Such properties in soft polymer-based piezoelectric materials were previously challenging and unachievable. The nanocomposite exhibits excellent ferroelectric properties with 11 times enhancement in remnant polarization compared to pristine PVDF in ambient conditions. The stored energy density (Us) is 39.43 mJ/cm3 for the PVDF-MoS2 film. These lead-free and soft polymer-based nanocomposites can bring remarkable advances in various flexible sensors, data storage, and energy harvesting applications.

Biomaterial systems for evaluating the influence of ECM mechanics on anti-fibrotic therapeutic efficacy

Cardiac fibrosis is characterized by excessive accumulation and deposition of ECM proteins. Cardiac fibrosis is commonly implicated in a variety of cardiovascular diseases, including post-myocardial infarction (MI). We have previously developed a dual-delivery nanogel therapeutic to deliver tissue plasminogen activator (tPA) and Y-27632 (a ROCK inhibitor) to address MI-associated coronary artery occlusion and downregulate cell-contractility mediated fibrotic responses. Initial in vitro studies were conducted on glass substrates. The study presented here employs the use of polyacrylamide (PA) gels and microgel thin films to mimic healthy and fibrotic cardiac tissue mechanics. Soft and stiff polyacrylamide substrates or high and low loss tangent microgel thin films were utilized to examine the influence of cell-substrate interactions on dual-loaded nanogel therapeutic efficacy. In the presence of Y-27632 containing nanogels, a reduction of fibrotic marker expression was noted on traditional PA gels mimicking healthy and fibrotic cardiac tissue mechanics. These findings differed on more physiologically relevant microgel thin films, where early treatment with the ROCK inhibitor intensified the fibrotic related responses.

Synergistic phases in isopropanol electrospun for Fe2O3/Fe3O4@C@MoS2 nanofibers for enhanced electromagnetic interference shielding characteristics and impedance analysis

Co-existence of phases in Fe2O3/Fe3O4@C@MoS2 nanofibers composite is synthesized via electrospinning and hydrothermal processes, where iso-propanol is utilized as a solvent. An extensive analysis is performed to evaluate the different properties, such as dielectric, morphological, structural, impedance, and electromagnetic shielding efficiency. A crystallite size of 24 nm is calculated using the Debye-Scherer formula. By using impedance spectroscopy, the electrical behavior of Fe2O3/Fe3O4@C@MoS2 nanofibers is described. Variations in frequency and temperature-dependent relaxation times are compared in an impedance plane plot. Changes in the conduction mechanism at different temperatures are observed. In Fe2O3/Fe3O4@C@MoS2 nanofibers composites, a number of distinctive characteristics in this work are explained, including stable dielectric constant, low tangent loss small polaronic hopping (SPH), and variable range hoping (VRH) model. The localization length of Fe2O3/Fe3O4@C@MoS2 nanofibers is calculated, 1/α = 1.2 Å. The typical EMI shielding efficiency of about 23 dB is demonstrated by the Fe2O3/Fe3O4@C@MoS2 nanofibers composite in the X-band frequency range. This extraordinary shielding capacity is observed in 3 mm thick nanofibers.

Significantly reduced the low-loss tangent in A2/3Cu3Ti4O12 (A = Gd and Sm) ceramics through a double-step calcination process

This study employs a method, integrating a double calcination process with a solid-state reaction, to diminish the loss tangent of Gd2/3Cu3Ti4O12 and Sm2/3Cu3Ti4O12 ceramics. Fine-grained microstructures can be detected in sintered Gd2/3Cu3Ti4O12 and Sm2/3Cu3Ti4O12 ceramics. The dielectric constants of Gd2/3Cu3Ti4O12 and Sm2/3Cu3Ti4O12 ceramics vary within the range of 4.14 × 103 to 6.82 × 103 at room temperature and 1 kHz. Additionally, Sm2/3Cu3Ti4O12 displays an impressively low loss tangent, ranging from 0.017 to 0.019. X-ray photoelectron spectroscopy can detect the presence of both Cu+/Cu2+ and Ti3+/Ti4+ states, which may be influenced by oxygen vacancies within the lattice. Theoretical calculations using density functional theory have demonstrated that both Sm and Gd ions can increase oxygen vacancy concentrations, leading to a reduction in the loss tangent of these ceramics. Moreover, electron density analysis revealed that the presence of oxygen vacancies in this structure is responsible for the Cu+ and Ti3+ states observed in our XPS experiments. Lastly, the observed dielectric response in both Gd2/3Cu3Ti4O12 and Sm2/3Cu3Ti4O12 ceramics is probably attributed to a heterogeneous microstructure and the cumulative effects arising from both the grain and grain boundaries.

Influence of underlayer roughness on the properties of Sc0.4Al0.6N thin films prepared via sputter deposition

Abstract A ScAlN thin film is one of the key materials of MEMS and high-frequency filters used in new-generation communication devices. Piezoelectricity can be improved by increasing Sc concentration. However, abnormal grains often appear at high Sc concentrations, degrading crystallinity and piezoelectricity. Herein, we demonstrated that underlayer roughness considerably affects the emergence of abnormal grains in a Sc0.4Al0.6N thin film formed via reactive DC sputtering. Dry etching with Ar plasma can effectively reduce the surface roughness of amorphous SiN and polycrystalline Si. Sc0.4Al0.6N thin films deposited on amorphous SiN and polycrystalline Si with sufficient flat surfaces exhibited a low density of abnormal grains, high crystallinity and piezoelectricity, and low loss tangent. Moreover, such high-quality thin films were obtained on a borophosphosilicate glass flattened using a reflow process without Ar etching. Therefore, underlayer roughness played an important role. The findings can help enable the large-scale production of highly doped ScAlN thin films.

Optimizing sintering conditions and microstructure for enhanced dielectric and humidity sensing properties of Na1/3Ca1/3Tb1/3Cu3Ti4O12 ceramics

This study investigated the impact of sintering temperature and resultant microstructure on the dielectric behavior and humidity sensing performance of Na1/3Ca1/3Tb1/3Cu3Ti4O12 (NCTCTO). The pure NCTCTO phase was obtained. Relative density and grain size tended to increase with the sintering temperature. The porous NCTCTO exhibited remarkable humidity sensing performance with minimal hysteresis error (2 %) and rapid response and recovery times (1.5 min). The dense NCTCTO ceramic with a high relative density of about 99 %, demonstrated significant giant dielectric properties, with ε′∼8500 and low loss tangent (0.08). The dielectric behavior was interpreted using the internal barrier layer capacitor model. The increase in ε′ with humidity was ascribed to the absorption of H2O molecules at the grain boundary, leading to increased interfacial polarization. This work delineates the critical influence of ceramic microstructure on the humidity sensing and giant dielectric properties of NCTCTO ceramics, paving the way for their application in advanced electronic devices.

High aspect ratio Na–Co-oxide ceramic filler composites with novel electrical and dielectric properties

Polymer composites with high aspect ratio Na–Co oxide ceramic filler – polymer matrix was investigated in this study. They demonstrate high dielectric permittivity, low dielectric loss tangent values which is useful for capacitive field grading and reversible voltage dependent electrical conductivity properties under an applied electric field which can be utilized for resistive field grading. These unique properties are useful for electrical stress control applications in power components. This study employs novel ceramic platelets as the varistor filler component in a polymer composite form, introducing a new class of materials to the world of electrical stress control technology. By minimizing the amount of varistor filler material required to very low levels (15 wt%), it is possible to develop lightweight non-linear dielectric composites that not only exhibit improved electrical characteristics but also make processing easier and open up new design space for making various components for electrical power applications. By utilizing novel NaxCoO2 (x < 1) ceramic fillers in composite form, we aim to contribute to the development of innovative nonlinear dielectric composites that can enhance the performance and processibility of various power system components under various working environments.

Phase formation and dielectric properties of MgFe2O4 nanoparticles synthesized by hydrothermal technique

In the recent development of energy storage devices, the scientific study has demonstrated a significant interest in the applications of the magnesium iron oxide (MgFe2O4) nanoparticles. In this work, we present synthesized novel MgFe2O4 nanoparticles at different molarities (0.1–0.5 M), via hydrothermal technique. An X-ray Diffractometer was used to study the phase analysis of the prepared samples at different molarities. A pure cubic phase of the MgFe2O4 is observed at molar concentrations of 0.3 M and 0.4 M. However, the mixed phases consisting of (MgFe2O4 + γ-Fe2O3) were also observed at 0.1 M, 0.2 M, and 0.5 M. The pure cubic MgFe2O4 nanoparticles depict the large value of crystallite size, 19.5 nm, and the lowest dislocation density and strain. The vibrating Sample Magnetometer shows the ferromagnetic nature of the pure MgFe2O4 with a high saturation magnetization. The value of saturation magnetization surged from 36.88 emu/g to 55.2 emu/g at 0.4 M concentration. The dielectric response of the materials as a function of applied frequency was studied thoroughly by using an Impedance Analyzer. The highest value of dielectric constant and low tangent loss was also reported at 0.4 M. Cole-Cole plots are the affirmation of the contribution of both grains and grain boundaries in the charge mechanism. These distinctive features make the synthesized material an excellent choice for future spintronics and energy storage devices.

Influence of strontium and donor ion substitution on the dielectric, optical, and nonlinear characteristics of (Ca0.9Sr0.1)0.95A0.033Cu3Ti4O12 ceramics

This study expands on a previous investigation by substituting lanthanum with various trivalent ions in the compound (Ca0.9Sr0.1)0.95A0.033Cu3Ti4O12 (A = La3+, Sm3+, Sc3+, Gd3+, Y3+ and Bi3+) through solid-state synthesis. The analysis includes microstructures, optical, dielectric, and nonlinear properties. Sr2+/A3+-doped CCTO exhibits a significant reduction in grain size. The doped samples display a band gap ranging from 3.22 eV to 3.36 eV, with high dielectric permittivity (ε'≈4.51 × 103-5.37 × 104). Additionally, Sr2+/A3+ doping enhances the thermal stability compared to pure CCTO ceramic. Specifically, Sr2+/Sc3+-doped compound shows low loss tangent (tanδ≈0.04) at 60 °C, with the dielectric loss remaining below 0.1 over a temperature range from 50 °C to 160 °C. Furthermore, there is a significant improvement in breakdown voltage (Eb = 8420 V/cm), which is 23 times higher than CCTO (362.5 V/cm), and the coefficient α increases from 3.28 to 12.76. These enhancements are attributed to inhibiting the formation of Ti3+ and reducing oxygen vacancies.

Characterizing interregional differences in the rheological properties and composition of rat small intestinal mucus.

The mucus layer in the small intestine is generally regarded as a barrier to drug absorption. However, the mucus layer is a complex system, and presently, only a few studies have been conducted to elucidate its physicochemical properties. The current study hypothesizes that the mucus layer contains solubility-enhancing surfactants and thus might aid the oral absorption of poorly water-soluble drugs.Mucus was sampled from sections of the small intestine of fasted rats to analyze the rheological properties and determine the mucus pH and concentrations of proteins and endogenous surfactants, i.e., bile salts, polar lipids, and neutral lipids.The mucus layer in the two proximal sections of the small intestine exhibited different rheological properties such as higher zero-shear viscosity and lower loss tangent and higher protein concentrations compared to all subsequent sections of the small intestine. The pH of the mucus layer was stable at ~ 6.5 throughout most of the small intestine, but increased to 7.5 in the ileum.The bile salt concentrations increased from the duodenum (16.0 ± 2.2mM) until the mid jejunum (55.1 ± 9.5mM), whereas the concentrations of polar lipids and neutral lipids decreased from the duodenum (17.4 ± 2.2mM and 37.8 ± 1.6mM, respectively) until the ileum (4.8 ± 0.4mM and 10.7 ± 1.1mM, respectively).In conclusion, the mucus layer of the rat small intestine contains endogenous surfactants at levels that might benefit solubilization and absorption of orally administered poorly water-soluble drugs.

Investigating the charge transport mechanism and dielectric properties in nickel oxide polyaniline nanocomposites

A simple precipitation method was employed to synthesise Nickel Oxide (NiO) nanoparticles and in-situ polymerization method was employed to synthesise Polyaniline (PANI) and PANI/NiO nanocomposites. To investigate the charge transport mechanism, DC and AC conductivity studies have been carried out. The drastic decrease in DC conductivity by two orders with an addition of NiO is noticed. Impedance and AC conductivity characteristics of these composites were examined in the frequency ranging from 10 Hz to 8 MHz. All samples obey Jonscher's Power law of disordered material at higher frequencies. The values of dielectric constant as well as dielectric loss decreased with an increase in applied frequency for all the samples. The samples show non-Debey relaxation mechanism verified by Havriliak – Negami model. Composite sample 5 wt % NiO show low tangent loss behaviour which are of importance in high frequency device applications. The obtained results are promising applications for energy storage applications and organic electronic devices.

Low loss and high dielectric BaTiO3@Al2O3 Core@Shell novel nanostructures by heteronucleation method

As-purchased BaTiO3, hydrothermally prepared BaTiO3, and BaTiO3@Al2O3 core@shell nanostructures through heteronucleation method were confirmed for structure/microstructure through XRD/ FESEM/HRTEM. High static dielectric constant of 2450 is obtained for BaTiO3@Al2O3 with a very low loss tangent (Tanδ ∼ 0.1), due to the outer thick insulating Al2O3 layer over BaTiO3. Jonscher’s law and Modulus spectra show a non-Debye type broad relaxation obeying a modified KWW function for BaTiO3, with no relaxation for BaTiO3@Al2O3, due to the suppression of dipoles by Al2O3. Higher dielectric field strength of ≥ 20 kV/cm was observed for BaTiO3@Al2O3 through the ferroelectric hysteresis loops.

Frequency selective surface filters with high-quality factors based on a Fano resonance.

In this work, we propose a design method of the narrow passband filter with a high Q-factor based on a Fano resonance. A single-layer metallic frequency selective surface (FSS) with a simple structure is first designed according to this idea, but the result is not satisfying since the filter transmittance will significantly decrease with the increase of the Q-factor due to the presence of an inherent ohmic damping. Further, to improve the design, a ceramic-based FSS filter based on the similar mechanism is proposed, and the requirements of the ultrahigh Q-factors can be met owing to the high permittivity and low loss tangent of microwave ceramics. The design strategy proposed in this paper may have a promising potential in modern wireless communication and related fields.

Existence of monoclinic and tetragonal zirconia in MgO substituted alumina zirconia composites and studies of dielectric behavior

Magnesia stabilized zirconia-alumina composite were processed by auto-combustion method followed by solid-state sintering. Tetragonal zirconia with orthorhombic alumina phase has been ensured from XRD patterns and from Raman spectra. The optical band gap energy for 2%, 4% and 6% magnesium oxide substituted zirconia-alumina composites are 4.91, 5.03 and 3.48 eV, respectively. The dielectric behavior between the frequency range of 1 kHz–1 MHz shows frequency independent nature of dielectric constant with low loss tangent at various temperatures. The non-Debye type and grain-grain boundary effects were confirmed from Nyquist plot. Both PTCR and NTCR behavior were observed from AC conductivity study.

Adamantane-based low-dielectric-constant photocurable resin for 3D printing electronics

In this work, a novel formulation is developed to prepare photocurable polyurethane acrylate (PUA) resin with a low dielectric constant for 3D printing applications. To amend the deficient electronic properties of regular 3D printed PUA materials, a symmetric polymer structure 1,3-adamantanediol (ADO) is introduced into the PUA polymer matrix to effectively decrease the dielectric constant. A low dielectric constant (Dk = 2.26) and a low loss tangent (Df = 0.018) at 10 GHz after formulation, are significantly lower than commercial PCB materials (High Tg FR-4, Dk = 4 and Df = 0.02). The modified PUA also exhibits great mechanical properties (tensile strength 12.02 MPa and elongation break at 111.35%) and can be further metalized with adhesive copper layers (5B adhesion test). With little addition of BN powder (1 wt%), the Df of PUA resin can also be effectively reduced (Df = 0.006), and the measured values of its metalized substrate antenna parameters are proven to be within the acceptable range for 5 G devices. The PUA resin can also be printed into complex 3D structures for 5 G flexible circuit board applications with good design flexibility, and the low dielectric constant provides the opportunity to replace traditional rigid FR-4 substrates for 5 G flexible board applications.