Loss Tangent Values Research Articles

Microstructures and Dielectric Permittivity Properties of Fe3O4/Cdots Nanocomposites Synthesized by Green Route Utilizing Moringa Oleifera Extract and Watermelon Peel

Dielectric materials are beneficial for storing electrical energy due to their insulating and polarization properties in response to external electric fields. Magnetite has shown promise as a dielectric material among other materials due to its good magnetic properties, low toxicity, and biocompatibility. However, the weakness of Fe3O4, which has low stability and easy agglomeration, requires a modification on its surface by using Carbon dots (Cdots). This research investigates the dielectric properties of Fe3O4/Cdots obtained through the green synthesis method. Fe3O4 nanoparticles were synthesized using the co-precipitation method with Moringa oleifera leaf extract as a reducing and stabilizing agent. In contrast, Cdots were synthesized using the hydrothermal method with watermelon peel waste as a carbon source. The Fe3O4 composite nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), ultraviolet-visible spectroscopy (UV-Vis), and impedance spectroscopy. The XRD spectra revealed the existence of cubic inverse spinel and a reduction in crystal size as the concentration of Cdots increased, measuring 7.8 and 7.1 nm, respectively. SEM-EDX revealed that the sample is composed of Fe, O, and C elements and has a spherical shape with Cdots distributed on the surface of Fe3O4. The UV-Vis spectrum showed the absorption peak of Cdots at 282 nm. The Fe3O4 absorption peak is identical to the Fe3O4/Cdots absorption peak at 193 nm. The increase in band gap energy from 2.96 to 3.33 eV is related to the increase in Cdots concentration. In the 10-900 kHz frequency range, dielectric property tests demonstrated peak dielectric permittivity values (real and imaginary). A substantial decrease was observed between 10 kHz and 200 kHz, followed by a relatively stable pattern up to 900 kHz. The loss tangent value obtained has a tanδ value <0.5, which means that the addition of Cdots affects reducing the energy loss stored in Fe3O4.

Dielectric Terahertz Characterization of Microwave Substrates and Dry Resist

Microwave fabrication and design techniques are commonly employed in the terahertz (THz) domain. However, a characterization of commercially available microwave dielectric materials is usually lacking at sub-THz and THz frequencies. In this work, we characterized four substrates by Rogers and an Ordyl dry resist between 0.2 and 2 THz, in terms of relative permittivity and loss tangent. The reflectance spectra of the investigated materials were retrieved by means of THz time-domain spectroscopy in reflection mode and post-processed according to a transmission-line model in which the materials’ parameters are fit by means of the Havriliak–Negami variation of the Debye model. The relative permittivity of the investigated materials showed negligible frequency dispersion in the sub-THz and in the THz range. In terms of the loss tangent, the Rogers substrates revealed a more pronounced frequency-dispersive behavior among different materials, as dictated by the Havriliak–Negami model. The Ordyl resist was dispersive in the 0.2–1.2 THz range and presented a nearly constant loss tangent value between 1.2 and 2 THz. These results may represent a reference for the development of innovative components for THz and sub-THz emerging applications.

Structural, morphological, dielectric, and electrical characteristics of a brownmillerite material for electronic devices: KBiMn2O5

The main objective this communication is to study the structural, morphological, dielectric, and electrical properties of a novel brownmillerite material, KBiMn2O5. Preliminary analysis of the X-ray diffraction (XRD) pattern with N-TREOR09 (trial and error method) with Le-Bail method shows monoclinic symmetry (a = 10.919 Å, b = 5.114 Å, c = 10.453 Å, β = 104.428˚). The examination of scanning electron microscopic spectrum provides the nature of the morphological surface of the sample having an average grain size of 19.89 μm. We have examined Maxwell-Wagner dielectric dispersion, relaxation, and transport mechanisms by analyzing the dielectric, impedance, and conductivity spectra across a wide range of experimental frequencies (1 kHz to 1 MHz) and temperatures (25°C to 500°C). The value of relative permittivity (εr) rapidly increases 200 (room temperature) to 85000 (500°C) with an increase in temperature from room temperature. The high value of εr shows colossal dielectric response (CDR) of the material. The low value of tangent loss (≥ 4.5) can also be applicable to electronic devices. On increasing frequency (1 kHz to 1 MHz), the activation energy of the charged ions from 0.391 eV to 0.328 eV shows a thermally activated relaxation mechanism in the material. The thermistor constant (β), determined as 6317.16, and the temperature coefficient of resistance (TCR) -0.00331 are suitable for high-temperature NTC thermistors, temperature sensors, and other electronic device applications. The study of room temperature non-Ohmic charge conduction and current-voltage charecteristics confirms the suitability of the material for devices.

The Effect of Whey Protein Concentrate, Soy Protein Isolate, and Xanthan Gum on Textural and Rheological Characteristics of Gluten-Free Batter and Cake

The market of gluten-free food products has been growing exponentially in recent years. Consequently, it is necessary to conduct research on the effects of various compounds to enhance the quality of these products. The present study is aimed at investigating the effects of adding whey protein concentrate (WPC) and soy protein isolate (SPI) at three levels (0%, 5%, and 10%) and xanthan gum (XG) (0%, 0.15%, and 0.3%) on the textural and rheological characteristics of gluten-free batter and cake based on rice flour. The results showed that increasing the levels of XG, WPC, and SPI improved the apparent viscosity of the batter samples. The effect of WPC on the apparent viscosity was more pronounced than that of SPI, as the highest value (21.9 Pa·s) was related to the sample containing 10% WPC and 0.3% XG. The loss tangent values of the batter samples, measured at a frequency of 1 Hz, ranged from 0.531 to 0.8 for different levels of WPC/XG and from 0.466 to 0.699 for SPI/XG, indicating a gel-like behavior of the batter samples. The sample containing 10% SPI and 0.3% XG displayed the strongest gel with higher storage modulus (982.112 Pa) and loss modulus (458.039 Pa) compared to other samples. Increasing the levels of XG, WPC, and SPI resulted in higher specific volume, porosity, firmness, and springiness of the samples compared to the control sample (P&lt;0.05). The addition of WPC, SPI, and XG improved the overall acceptability of the cake samples, with the samples containing WPC/XG combination being the most preferred. Ultimately, the cake sample containing 10% WPC along with 0.3% XG introduced as optimal sample. This formulation not only can enhance the characteristics of gluten-free cake but also meets parts of the nutritional needs of consumers, particularly those with celiac disease.

Notably enhanced dielectric response with low loss in PVDF composites filled with RuO2–BaTiO3 hybrid particles

This study delineates the process of fabricating and the results of investigating the dielectric properties of hybrid particles created through the integration of Poly(vinylidene fluoride) (PVDF) filled with RuO2 coated on BaTiO3 nanoparticles (nBT), designated as RuO2–nBT. These hybrid particles were successfully synthesized employing a simple and cost–effective solid–state reaction method. The inclusion of RuO2–nBT in the PVDF matrix engendered a notable enhancement in its dielectric properties. Notably, a RuO2–nBT fraction of 0.5 manifested a dielectric constant (ε′) of 107.4 and a dielectric loss tangent (tanδ) value of 0.062 at 30 °C and 1 kHz. These findings signify the effective role of interfacial polarization occurring between the PVDF matrix and the RuO2–nBT hybrid particles, leading to a marked improvement in dielectric attributes. Moreover, the observed low tanδ value indicates the elimination of conductive pathways, an inhibitory effect attributed to the incorporation of RuO2–nBT hybrid particles. This study underscores the promising potential of RuO2–nBT hybrid particles in fine–tuning and augmenting the dielectric properties of polymer composites, particularly in scenarios necessitating low tanδ and high ε′ values.

Polyvinylpyrrolidone – KNNLST lead-free ceramic composites for dielectric applications

Piezoelectric composites offer many advantages compared to piezoelectric ceramics or polymers because of their mechanical flexibility and relatively high stress-induced voltage. In this research, high-molecular weight polyvinylpyrrolidone (PVP) and lead-free piezoelectric (K0.45Na0.51Li0.04) (Nb0.85Ta0.1Sb0.05)O3 (KNNLST) ceramics have been used to produce composites. The possible range of composites from 0 to 100 wt% has been explored. The ceramics were produced using conventional processing methods, while the composites were solution-cast after being mixed with a magnetic stirrer. The composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and dielectric and piezoelectric characterization to determine their properties. The morphology of the composites indicates the homogeneous distribution of the ceramics in the polymer. The XRD patterns show that the dissolved amorphous PVP precipitates and the addition of KNNLST ceramics contributes substantially to the crystalline phase formation. The relative permittivity and loss tangent values increase with an increase in ceramic content. Acceptable polarization and strain hysteresis curves were obtained only for the KNNLST ceramics. The composites produced will be suitable for dielectric applications.

Structural, Morphological, Spectroscopic, and Dielectric Properties of Ca-Mg Nanoferrites for High-frequency Applications

Introduction:: Ca-Mg nanoferrites of composition Ca0.5Mg0.5Fe2O4 were synthesized by wet chemical citrate precursor approach. Methods:: The prepared nanoparticles were characterized by an “X-ray diffractometer, Scanning electron microscopy, Diffused reflectance spectroscopy, and Impedance analyzer”. In the XRD pattern, the most intense reflection was observed from the (311) peak that corresponds to the cubic spinel phase of the prepared ferrite. Results:: The average size of all crystallites was calculated to be 19 nm. The sample's porosity was found to be 61%. In the SEM micrograph, uniformity in the size of the particles was detected with some agglomeration. The calculated energy band gap (1.91eV) reveals the semiconducting nature of the prepared material. Conclusion:: The high value of the real part of the dielectric constant (290) and the low value of loss tangent (0.17) reveals that the synthesized material can be useful in magnetic cores, microwave components, and other high-frequency applications.

Structural and electrical characteristics of manganese modified BaTiO3 ceramic

The material Ba(Ti0.5Mn0.5)O3 synthesized through the conventional solid-state reaction method has hexagonal structure free from any impurity phase. The complex dielectric dispersion, temperature and frequency-dependent dielectric, impedance, AC conductivity, and leakage behavior of the sample are studied. The impedance study of the material encloses non-Debye type relaxation, negative temperature coefficient of resistance nature and the grain and grain boundary effects. The ferroelectric to paraelectric phase transition occurs at T C ∼ 270 °C. The dielectric constant and loss-tangent values are found to be less as compared to that of the parent barium titanate sample. R g < R gb, that is, grain boundary has greater opposition than the grain region. The material follows correlated barrier hopping model. The carrier transport process through AC conductivity study obeys the Jonscher’s power law and the Arrhenius relation while varying with the frequency and temperature.

Experimental Investigation of Mechanical and Electromagnetic Performance of Asphalt Concrete Containing Different Ratios of Graphite Powder as a Filler to be Potentially Used as Part of Wireless Electric Roads

This study experimentally investigates the usability of asphalt concrete pavement containing five different ratios of graphite powder (0%, 1.25%, 2.5%, 3.75% and 5% by weight of the aggregate blend or 0%, 25%, 50%, 75% and 100% of the filler content) as a filler to be potentially used as part of wireless electric roads (ER). As part of the study, first, optimum asphalt binder content for the asphalt mixes without graphite powder was determined as 5%. Then, using the determined optimum asphalt binder content, asphalt mixes containing five different ratios of graphite powder as a filler were prepared and their mechanical and volumetric properties based on Marshall mix design methodology were evaluated. As graphite powder ratios in the asphalt mixes increased, their Marshall stability, flow, voids filled with asphalt and unit weight test results mostly decreased but their air content and voids in mineral aggregate test results increased. Possible reasons for this could be: (1) lower bulk specific gravity of graphite powder, (2) higher asphalt absorbance, (3) having greater surface area compared to that of limestone filler, and (4) weak bonds between sheet-like graphite layers. Furthermore, another batch of asphalt mixes containing five different ratios of graphite powder were prepared and tested in the frequency range of 3–18 GHz for their electromagnetic permittivity properties. It was observed in this study that, except for the specimens with 100% graphite powder ratios, transmission magnitudes of all specimens were above 50% up to 8 GHz, indicating that they had comparably high transmission magnitudes so as comparably low tangent loss values. In the frequency range of 3–13 GHz, transmission magnitudes of the specimens with 25% and 50% graphite powder ratios were consistently higher than that having no graphite powder, the ones with 25% powder ratios had the highest transmission magnitudes in most of the cases in this frequency range. Considering the mechanical, volumetric and electromagnetic property test results of the asphalt mixes with five different ratios of graphite powder, it can be concluded that the use of 25% graphite powder ratio (corresponding to 1.25% of the aggregate blend used in the mixes), has a comparably lower negative effect on mechanical and volumetric properties of asphalt mixes and has a positive effect on electromagnetic permittivity properties of asphalt mixes. Asphalt mixes produced with this graphite powder ratio can be considered to be used as part of wireless ER.

Experimental Investigation of Mechanical and Electromagnetic Performance of Asphalt Concrete Containing Different Ratios of Graphite Powder as a Filler to be Potentially Used as Part of Wireless Electric Roads

This study experimentally investigates the usability of asphalt concrete pavement containing five different ratios of graphite powder (0%, 1.25%, 2.5%, 3.75% and 5% by weight of the aggregate blend or 0%, 25%, 50%, 75% and 100% of the filler content) as a filler to be potentially used as part of wireless electric roads (ER). As part of the study, first, optimum asphalt binder content for the asphalt mixes without graphite powder was determined as 5%. Then, using the determined optimum asphalt binder content, asphalt mixes containing five different ratios of graphite powder as a filler were prepared and their mechanical and volumetric properties based on Marshall mix design methodology were evaluated. As graphite powder ratios in the asphalt mixes increased, their Marshall stability, flow, voids filled with asphalt and unit weight test results mostly decreased but their air content and voids in mineral aggregate test results increased. Possible reasons for this could be: (1) lower bulk specific gravity of graphite powder, (2) higher asphalt absorbance, (3) having greater surface area compared to that of limestone filler, and (4) weak bonds between sheet-like graphite layers. Furthermore, another batch of asphalt mixes containing five different ratios of graphite powder were prepared and tested in the frequency range of 3–18 GHz for their electromagnetic permittivity properties. It was observed in this study that, except for the specimens with 100% graphite powder ratios, transmission magnitudes of all specimens were above 50% up to 8 GHz, indicating that they had comparably high transmission magnitudes so as comparably low tangent loss values. In the frequency range of 3–13 GHz, transmission magnitudes of the specimens with 25% and 50% graphite powder ratios were consistently higher than that having no graphite powder, the ones with 25% powder ratios had the highest transmission magnitudes in most of the cases in this frequency range. Considering the mechanical, volumetric and electromagnetic property test results of the asphalt mixes with five different ratios of graphite powder, it can be concluded that the use of 25% graphite powder ratio (corresponding to 1.25% of the aggregate blend used in the mixes), has a comparably lower negative effect on mechanical and volumetric properties of asphalt mixes and has a positive effect on electromagnetic permittivity properties of asphalt mixes. Asphalt mixes produced with this graphite powder ratio can be considered to be used as part of wireless ER.

Synergistic effect of CaCu3Ti4O12 ceramic and Ti3C2Tx MXene nanoflakes on the dielectric properties of poly (vinylidene fluoride) composites

Polymer composites are popular multifunctional materials. Their effective use in elements of electronic devices is possible due to the optimal dielectric properties. In this work, a balance between a high dielectric constant and a low dielectric loss tangent was achieved by introducing two types of fillers into poly (vinylidene fluoride): ceramic CaCu3Ti4O12 (10, 20 and 30 vol%) and conductive Ti3C2Tx MXene (2.5–5 wt%). CCTO ceramics was synthesized by the solid-state method. Ti3C2Tx MXene was obtained by etching the Al layer from Ti3AlC2 MAX phase under hydrothermal conditions. The materials were studied by XRD, SEM, FTIR, laser diffraction, and impedance spectroscopy. Composites based on poly (vinylidene fluoride) with 30 vol% CaCu3Ti4O12 and 5 wt% Ti3C2Tx MXene demonstrated the most promising results when increasing the dielectric constant to 28 at a dielectric loss tangent value of 0.061 at a frequency of 10 kHz. At the same time, the electrical strength of the composites had values not lower than 100 MV∙m−1, which is extremely important for their practical application. The results obtained can be used in the development of modern polymer composite dielectrics for passive elements of flexible electronics.

Additively manufactured rectangular waveguides for the electromagnetic characterization of materials using the transmission/reflection line method

PurposeRadio frequency (RF) technology relies on the electromagnetic properties of the materials used, which includes their complex permittivities and loss tangents. To measure these properties, techniques for material characterization such as the transmission/reflection method are used in conjunction with conversion techniques to calculate these values from scattering parameters. Unfortunately, these techniques rely on relatively expensive rectangular waveguide adaptors and components, especially if testing over large frequency ranges. This paper aims to overcome this challenge by developing a more affordable test equipment solution based on additively manufactured waveguide sections.Design/methodology/approachTo evaluate the effectiveness of using additively manufactured waveguides to perform electromagnetic characterization with the transmission/reflection method, samples of PLA Tough with varying infill percentages and samples made from several Formlabs photopolymer resins are fabricated and analyzed.FindingsResults show that the method yielded permittivity and loss tangent values for the measured materials that generally agree with those found in the literature, supporting its credibility.Originality/valueThe accessibility of this measurement technique will ideally allow for more electromagnetic material characterization to occur and expand the possible use of additive manufacturing in future RF designs. This work also provides characterization of several Formlabs photopolymer resins, which have not been widely analyzed in the current literature.

Simulation of a Permittivity Measurement System with Microstrip Structure at ISM Frequency Incorporate with Lookup Table

This research aims to simulate a permittivity measurement system utilizing a microstrip structure with sonnet software to bring the discovered knowledge to develop the permittivity measurement instrument that has high efficiency and low cost in the next. This research has designed and simulated microstrip structure at ISM frequencies of 13, 27, and 40 MHz, for permittivity values of 35, 55, and 75 are used, also loss tangent values of 0.2, 0.4, and 0.6 are used, and conduct the simulation measurement system for creating a lookup table size of 11x11, 5x5, and 3x3 respectively. Then, bring the results from the simulation to calculate to find the permittivity values and loss tangent values. After, find the error values. The research results found that directly calculating permittivity and loss tangent from S-parameters results in significantly high percentage errors. Therefore, the researcher will propose a method to find values from a lookup table. The results obtained from the proposed method exhibit consistency with the actual permittivity through errors that are below 0.1984 percent. Thus, the simulations of the measurement system in this research can apply to find permittivity values and loss tangent values of material having unknown values. Moreover, it is still able to develop into an actual measuring device that possesses both efficiency and worth in the future.

Enhancing the optical, electrical, dielectric properties and antimicrobial activity of chitosan/gelatin incorporated with Co-doped ZnO nanoparticles: Nanocomposites for use in energy storage and food packaging

The solution casting method was utilized to produce a brand of new nanocomposites made of chitosan (Cs), gelatin (Ge), and co-doped ZnO nanoparticles (NPs). The physicochemical characteristics of these nanocomposites were examined using a variety of methods. The doped samples' XRD patterns clearly demonstrated changes in the structural features of the Cs/Ge host polymer, with the widening of the peak at 2θ = 20.31 becoming more prominent as Co-doped ZnO NPs concentration increased. Tauc's relation was utilized to describe the direct and indirect bandgap energies using UV–Vis analysis. By including 3.5 wt% of Co-doped ZnO NPs, the optical energy gap direct and indirect of pure Cs/Ge was reduced from 5.22 to 4.92 eV to 4.90 and 4.42 eV, respectively. Co-doped ZnO NPs reinforcing has a significant impact on the in ac conductivity, dielectric constant and loss tangent values. An ionic conductivity of 1.089 × 10−7 S/cm at Cs/Ge-3.5 wt% Co-doped ZnO NPs was observed. The nanocomposites' antimicrobial effect on bacteria and fungi was tested. The adding of 3.5 %Co-doped ZnO NPs improved the activity against S. aureus (22 mm), E. coli (13 mm), A. niger (29 mm), and C. albicans (27 mm) despite the fact that the investigated pure mix had no effect on the microbiological strains. The current research's remarkable findings in terms of optical, dielectric, electrical, and antimicrobial effects indicate that Cs/Ge-coated ZnO film will have significant uses in both food packaging and energy storage devices.

Effect of sintering conditions on colossal dielectric properties of (Tb1/2Nb1/2)0.01Ti0.99O2 ceramics

In this study, we investigated various sintering temperatures (1200 °C−1450 °C) and durations (2–6 h) conditions for preparing (Tb1/2Nb1/2)0.01Ti0.99O2 (TNTO) ceramics. By employing high sintering temperatures (≥1350 °C) and extended sintering durations (≥4 h), we successfully achieved ultra–high dielectric permittivity values (ε′ ∼ 2.2 − 4.1 × 104) and remarkably low loss tangent values (∼0.025−0.079). Remarkably, the temperature coefficient of the TNTO ceramic, sintered at 1350 °C, exhibited exceptional stability, maintaining a value of approximately 15% even at 200 °C. Additionally, we examined the phase structure and microstructure of the TNTO ceramics to gain insights into their colossal permittivity (CP) behavior. The analysis revealed the presence of rutile TiO2 and TbNbTiO6 phases, and the ceramics exhibited a high–density microstructure under high–temperature sintering conditions. The impedance spectroscopy analysis revealed that the primary contributor to the observed CP behavior was the interfacial polarization mechanism. The observed increase in the ε′ value, correlated with the enlargement of the average grain size, can be attributed to the effect of the internal barrier layer capacitor. However, when the sintering time ≥4 h, the grain size did not significantly affect the ε′ value, possibly due to reaching the maximum capacity of electron production for the interfacial polarization process (i.e., the maximum intensity of polarizability). This study provides valuable insights into optimizing the sintering conditions for TNTO ceramics and related compounds, laying the groundwork for the development of a new CP oxide suitable for practical applications.

Electrical, Dielectric, and Magnetic Characteristics of (BiBa)(FeMn2)O8

A new compound of chemical formula (BiBa)(FeMn2)O8 is prepared by a solid‐state reaction method. X‐ray structural studies confirm orthorhombic unit cell of the compound. Room‐temperature magnetic data display ferromagnetic hysteresis loop with high value of effective magnetic moments. The dependence of dielectric constant, loss tangent, impedance, and the conductivity at different frequencies (1 kHz−1 MHz) are measured using LCR meter on rise of temperature from room temperature to 500 °C. The dielectric constant increases on rise of temperature due to Maxell–Wagner polarization, and the loss tangent displays similar behavior. A low value of loss tangent is obtained at higher frequencies, which paves the way for the application of the compound in high‐frequency devices. The real impedance of the compound decreases indicating NTCR (negative temperature coefficient of resistance) behavior, and the imaginary impedance displays relaxor behavior. The Nyquist plot fits to a series combination of two RQC circuits ((RQC)(RQC)) and indicates the presence of non‐Debye relaxation. The frequency variation of conductivity obeys Jonscher's power law and reveals different conduction mechanisms in grain and grain boundary regions.

Evidence of Widespread Volcanic Activity near Hebrus Valles on Mars Revealed by SHARAD

Hebrus Valles is an outflow channel system in the plain-forming terrains of southeastern Utopia Planitia, Mars. These terrains may have formed through a combination of liquid water and volcanic processes, yet their nature, subsurface structure, and composition remain unclear. We investigate these terrains by mapping subsurface reflectors across 540 Shallow Radar (SHARAD) profiles and applying two complementary loss tangent inversion techniques. We find moderate loss tangent values across some subregions of Granicus Valles and Hyblaeus Fossae (tan δ = 0.0162 ± 0.0004 and tan δ = 0.019 ± 0.002, respectively), suggesting the presence of basaltic lava flows. We interpret non-detections in the other flows in Granicus Valles to be due to the presence of radar-lossy materials formed through aqueous processes, which supports the hypothesized occurrence of lahars in this region. A small area near Hebrus Valles exhibits subsurface reflectors with low to moderate loss tangents (tan δ = 0.010 ± 0.003), suggesting the presence of pristine lava flows or sedimentary materials capped by lava flows. We also find a widespread occurrence of very low-loss tangent materials near Hyblaeus Dorsa (tan δ = 0.0045 ± 0.0002), which may represent a lobe of the Medusae Fossae Formation or similar high-porosity materials buried underneath a lava flow. Together, these findings suggest that volcanic activity played a central role in the formation of terrains across the broader Hebrus Valles region.

Electrophysical Properties of PZT-Type Ceramics Obtained by Two Sintering Methods

This study demonstrates the impact of two sintering techniques on the fundamental properties of doped PZT-type ceramic materials (with Mn4+, Sb3+, Gd3+, and W6+), with the general chemical formula Pb(Zr0.49Ti0.51)0.94Mn0.021Sb0.016Gd0.012W0.012O3. The synthesis of ceramic powders was carried out through the calcination method. Two different methods were used in the final sintering process: (i) pressureless sintering (PS) and (ii) hot pressing (HP). The PZT-type ceramics were subjected to electrophysical measurements, encompassing various analyses such as X-ray diffraction (XRD), microstructure (scanning electron microscopy (SEM)), ferroelectric and dielectric properties, and DC electrical conductivity. The analysis of the crystal structure at room temperature showed that the material belongs to the perovskite structure from the tetragonal phase (P4mm space group) without foreign phases. Both sintering methods ensure obtaining the material with appropriate dielectric and ferroelectric parameters, and the tests carried out verified that the ceramic materials have a diverse range of parameters appropriate for use in micromechatronic and microelectronic applications. The obtained ceramic material has high permittivity values, low dielectric loss tangent values, and high resistance. At room temperature, the ceramic samples’ P-E hysteresis loops do not saturate at a field of 3.5 kV/mm (Pm maximum polarization is in the range from 12.24 to 13.47 μC/cm2). However, at higher temperatures, the P-E hysteresis loops become highly saturated, and, at 110 °C, the Pm maximum polarization values are in the range from 28.02 to 30.83 μC/cm2.

Valorization of ripe banana peels and cocoa pod husk hydrochars as green sustainable “low loss” dielectric materials

The banana and cocoa crops are relevant worldwide and tons of their residues do not enter the industrial value chain. With this in mind, it is imperative to find alternative uses for these residues that could lead to novel and sustainable applications in diverse fields, such as consumer electronics. Lignocellulosic residues can be hydrothermally carbonized to produce a solid fraction called hydrochar. In this work, the dielectric characteristics of ripe banana peels and cocoa pod husks hydrochars are explored. Hydrothermal carbonization (HTC) treatments were carried out at two temperatures (150 °C and 210 °C) and three HTC times (2 h, 4 h, and 6 h). The materials were characterized electrically using a Semiconductor Analyzer under frequency swepts of 1 KHz to 1 MHz. Cocoa pod husk hydrochars (CHH) showed less variability in relative permittivity values compared to ripe banana peel hydrochars (BPH). The relative permittivity values of CHH ranged between 9.83 and 10.29 (150 °C) and 8.25–9.39 (210 °C), while for BPH, these values ranged between 6.89 and 14.14 (150 °C) and 6.39–8.77 (210 °C). In addition, the loss tangent values of CHH varied from 0.034 to 0.041 (150 °C) and from 0.036 to 0.038 (210 °C), while in BPH, these values varied from 0.056 to 0.091 (150 °C) and from 0.046 to 0.051 (210 °C). In both cases, HTC produced highly stable materials with low loss tangent values, making them good candidates for insulation and possessing good dielectric properties that can be further processed for downstream applications in the electronics industry.

Magnetic and Electrical Characteristics of Nd3+ and Mn2+-Co-doped Calcium Molybdato-Tungstates Single Crystals.

Single crystals of Ca1-3x-yMny□xNd2x(MoO4)1-3x(WO4)3x molybdato-tungstates (□ denotes vacant sites) with a scheelite-type structure have been successfully grown by the Czochralski technique in an inert atmosphere. This paper presents the results of structural, optical, magnetic, and electrical properties, as well as the broadband dielectric spectroscopy measurements of single crystals with different Nd3+ ion concentrations, i.e., when x = 0.0050 or x = 0.0098, and with constant content of Mn2+ ions, i.e., when y = 0.0050. Our magnetic studies have shown that substitution of diamagnetic Ca2+ ions in the CaMoO4 matrix with paramagnetic Nd3+ ones with a content not exceeding 0.02 and having a screened 4f-shell revealed a significant effect of orbital diamagnetism and Van Vleck's paramagnetism. Both single crystals have revealed residual electrical conductivity without an intrinsic region and a change of sign of the Seebeck coefficient at ca. 230 K. Dielectric spectroscopy measurements have shown constant values of relative permittivity (εr ∼ 8) and loss tangent (tan δ ∼ 0.01) both up to 400 K and up to 1 MHz, as well as the Fermi energy (∼0.04 eV) and the Fermi temperature (∼500 K) determined for both crystals from the diffusion component of thermopower. These results suggest the presence of shallow acceptor and donor levels in the studied crystals.