Small Dielectric Loss Research Articles

Ultralow dielectric loss of Y and Mn alternately doped nonstoichiometric BST films

ABSTRACTA 1% Y and 1% Mn alternately doped nonstoichiometric (Ba0.6Sr0.4)0.8TiO3 (Y/Mn-BST) film was attempted to design and prepare by an improved sol-gel method on Pt/Ti/SiO2/Si substrates, and its ultralow dielectric loss with other dielectric properties was studied in this paper. Undoped, Y doped and Mn doped BST films were also compared. All films grow along (110) orientation and show polycrystalline cubic ABO3 perovskite structures. Pure film shows the weakest crystallization, while Y/Mn-BST film exhibits the strongest crystallization. Superfluous Ti acted as Ti doping makes B sites so saturated that superfluous Ti4+ ions have to enter A sites and first replace Sr2+ ions and then replace Ba2+ ions to show donor doping, thus result in the smallest lattice parameter and decreased Ba/Sr ratio. Doped Y3+ or Mn2+ ions only enter A sites and replace Ti4+ ions to reveal acceptor doping, and thuscause lattice parameters and Ba/Sr ratio a little larger than the undoped BST film. The Y/Mn-BST film shows the largest lattice parameter and increased Ba/Sr ratio with acceptor doping. Each nonstoichiometric BST film show smaller capacitance, tunability and dielectric loss than normal BST film, but the Y/Mn-BST film reveals better combination of dielectric properties in particular much smaller dielectric losses of 0.0051∼0.0067, thus show more obvious practicability and reliability in tunable microwave applications.

Improved Triboelectric Nanogenerator Output Performance through Polymer Nanocomposites Filled with Core-shell-Structured Particles.

Core-shell-structured BaTiO3-poly( tert-butyl acrylate) (P tBA) nanoparticles are successfully prepared by in situ atom transfer radical polymerization of tert-butyl acrylate ( tBA) on BaTiO3 nanoparticle surface. The thickness of the P tBA shell layer could be controlled by adjusting the feed ratio of tBA to BaTiO3. The BaTiO3-P tBA nanoparticles are introduced into poly(vinylidene fluoride) (PVDF) matrix to form a BaTiO3-P tBA/PVDF nanocomposite. The nanocomposites keep the flexibility of the PVDF matrix with enhanced dielectric constant (∼15@100 Hz) because of the high permittivity of inorganic particles and the ester functional groups in the P tBA. Furthermore, the BaTiO3-P tBA/PVDF nanocomposites demonstrate the inherent small dielectric loss of the PVDF matrix in the tested frequency range. The high electric field dielectric constant of the nanocomposite film was investigated by polarization hysteresis loops. The high electric field effective dielectric constant of the nanocomposite is 26.5 at 150 MV/m. The output current density of the nanocomposite-based triboelectric nanogenerator (TENG) is 2.1 μA/cm2, which is above 2.5 times higher than the corresponding pure PVDF-based TENG.

Dielectric Loss Suppression of Silver/Poly(vinylidene fluoride) Composite Films with Polydopamine

ABSTRACTThe preparation and dielectric properties of silver-polydopamine/poly(vinylidene fluoride) (Ag-PDOP/PVDF) composite films with suppressed dielectric loss are reported. The dielectric loss tangents of the composite films were found to be rather low similar to that of pure PVDF over the frequency range 100 Hz to 30 kHz, almost regardless of the Ag content, and even lower than that of pristine PVDF in the relatively high frequency region. The nanoscale structure comprised of Ag nanoparticles (Ag NPs), isolated by the PDOP coating and the PVDF matrix, hindered the formation of percolative networks, resulting in the decreased conduction loss in the composite films, even at a high filler loading. The strong interfacial interaction between the Ag@PDOP particles and the PVDF matrix also contributed to the restrained interfacial loss. Consequently, these composite films had higher permittivity and smaller dielectric loss than the PVDF matrix at relatively high frequencies, and would thus be attractive for physically small capacitor applications in electronics and electric power systems.

Highly Dispersible Buckled Nanospring Carbon Nanotubes for Polymer Nano Composites

We propose the unique structure of highly dispersible single-walled carbon nanotubes (SWCNTs) in various solvents and polymers using the ZnO nano particle template. Buckled nanospring-shaped carbon nanotubes (NS-CNTs) were synthesized by a chemical reaction of ZnO nanoparticles with acid-treated SWCNTs and then dissolving ZnO through chemical etching. The unique structure of distorted hexagonal NS-CNTs encircled around ZnO nanoparticles was formed by the bending of SWCNTs caused by the agglomeration of chemically adsorbed Zn(OH)2, which is further crystallized as the polycrystalline ZnO inner core. The highly dispersible NS-CNTs could be incorporated in the poly[(vinylidenefluoride-co-trifluoroethylene] [P(VDF-TrFE)] copolymer, one of widely studied ferro- and piezo-electric polymer, up to the value of 15 wt% as nanofillers. The relative dielectric constant (K) of polymer nanocomposite, at 1 kHz, was greatly enhanced from 12.7 to the value of 62.5 at 11 wt% of NS-CNTs, corresponding to a 492% increase compared to that of pristine P(VDF-TrFE) with only a small dielectric loss tangent (D) of 0.1.

Relaxor phenomenon of (1-x)(Ba.85Ca.15)(Zr.09Ti.91)O3-xTa + 0.6 wt% Li2CO3 ceramics with high piezoelectric constant and Curie temperature

In the work, Ta2O5 doped (Ba.85Ca.15)(Zr.09Ti.91)O3 + 0.6 wt% Li2CO3 ceramics were successfully fabricated by the conventional solid state sintering method. Piezoelectric performance of the ceramics was significantly enhanced by doping the tantalum oxide, the optimum properties were obtained at x = 0.04 wt%, (d33~326 pC/N, kp~63% and Tc~129 °C, respectively). The Tc drastically increased compared with previous results. Besides, the microstructure, dielectric and ferroelectric properties were carefully investigated. The temperature-dependent dielectric performance of the specimens exhibits obvious relaxor phenomenon under various frequencies. The relaxor characteristics and XRD were systematically discussed, which certified that the samples were relaxor ferroelectrics with a small dielectric loss (0.62%) and a large dielectric constant (13693).

Effects of sintering temperature and KBT content on microstructure and electrical properties of (Bi.5Na.5)TiO3-BaTiO3-(Bi.5K.5)TiO3 Pb-free ceramics

A route exploring the morphotropic phase boundaries (MPB) region in (Bi.5Na.5)TiO3-BaTiO3-(Bi.5K.5)TiO3 ternary system has been designed based on the phase diagram. X-ray diffraction (XRD) has been performed to determine the phases of the prepared samples. The dielectric, ferroelectric, and piezoelectric properties of [(1-x) 0.9363(Bi.5Na.5)TiO3–0.0637BaTiO3]-x(Bi.5K.5)TiO3 (BNKBT100x) ternary lead-free piezoelectric ceramics are investigated as the functions of x and sintering temperature. When x was varied from 0 to 0.11, the BNKBT100x ceramics show single perovskite structure sintered at 1130–1210 °C. These ceramics show large dielectric permittivity, small dielectric loss, and diffused phase transition behavior. Well-defined ferroelectric polarization-electric field (P-E) hysteresis loop and relative large piezoelectric and electromechanical coefficients are also found in these ceramics. When increasing x, the electrical performances first increase, then decrease. The same rule is found when varying the sintering temperature. The optimized composition and sintering temperature are finally obtained.

Domain engineering enhanced microwave tunability in nonstoichiometric Ba0.8Sr0.2TiO3

AbstractDomain engineering via oxygen vacancy, , loading achieved by A/B modification as well as quenching treatment, was utilized for Ba0.8Sr0.2TiO3 (0.8 BSTs) in an attempt to enhance the microwave tunable characteristics. For similar grain sizes, the domain sizes were notably reduced for all nonstoichiometric BSTs, indicating that the loaded (as a consequence of Ti defects, ) played a role in the nuclei for new domain walls. The tunability T at 100 MHz under a direct current field of 30 V/20 μm increased steadily as the domain size (d.s.) declined for all BSTs, regardless of the A/B ratio, due to the d.s. effect. The tunable characteristics in nonstoichiometric BSTs having a similar d.s. of ˜190 nm were then compared. The tunability and tan δ decreased for A/B = 1.002 (0.2 mol% Ti defects). The introduced formed pinning centers that restricted domain wall motion, leading directly to lower tunability and smaller dielectric loss. However, ‐overloaded samples (i.e., A/B ≥ 1.005) exhibited increased values for tan δ due to conduction in the domains. The quench treatment of 0.8 BST (with A/B = 1.002) samples resulted in a d.s. reduction from 191 to 170 nm. These quenched specimens showed greater tunability, Ttotal, originating from the strengthened dipole contribution, Tdipole, as a consequence of the d.s. effect. The tan δ of the quenched specimens was essentially unchanged, indicating a homogenous distribution via the quench, effectively reducing the mobile (which contributes to electrical conduction) in the domains. Consequently, the achieved figure of merit via domain engineering was 2.25 at 100 MHz for the quenched BST with A/B = 1.002, which was 1.54 times larger than that of unmodified BST.

Compositionally Graded Multilayer Ceramic Capacitors

Multilayer ceramic capacitors (MLCC) are widely used in consumer electronics. Here, we provide a transformative method for achieving high dielectric response and tunability over a wide temperature range through design of compositionally graded multilayer (CGML) architecture. Compositionally graded MLCCs were found to exhibit enhanced dielectric tunability (70%) along with small dielectric losses (<2.5%) over the required temperature ranges specified in the standard industrial classifications. The compositional grading resulted in generation of internal bias field which enhanced the tunability due to increased nonlinearity. The electric field tunability of MLCCs provides an important avenue for design of miniature filters and power converters.

Deposition of YBCO Thin Films in View of Microwave Applications

In preparation for the future characterization of the microwave properties of pulsed laser deposited high-temperature superconductor YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6+x</sub> (YBCO) thin films, a YBCO growth optimization is performed using different substrate materials that have both a small dielectric constant and a small dielectric loss tangent. At first, the effect of thermal contact between a SrTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> substrate and the sample holder is investigated by comparing silver paste and a mechanical attaching mask as fixing techniques. Hence, the thermal contact is observed to be a crucial parameter for successful growth, while the effect of lattice mismatch when using, e.g., MgO, SrLaAlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , NdGaO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , and (LaAlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> (Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> AlTaO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> , is seen to be less important. In addition, the preliminary reflectiontype measurements for a meander-type coplanar stripline YBCO resonator are implemented and a comparison between the calculated and experimentally determined field-dependent frequency values is obtained.

Effects of hydrogen bonding between pyrrole-2-carboxaldehyde and nearest polar and nonpolar environment

The present paper represents dominant effects of hydrogen bonding on the existence of different molecular aggregates in one of the heterocyclic pyrrole system: pyrrole-2-carboxaldehyde (PCL). Theoretical and experimental Raman spectral evidence verifies the existence of different molecular aggregates like dimeric, monomeric, hydrated complex states in PCL. Atoms in molecules (AIMs) analysis and fluorescence decay profile provide a strong signature of intermolecular hydrogen bonding (IerHB) as the possible reason for the existence of cis form of dimeric (X) molecular aggregates. The high remnant polarization of 3.13μCcm−2 and smaller dielectric loss in solid form of PCL arise due to in X by ordering of dipoles as a result of IerHB. A remarkable high ferroelectric response in solid phase makes PCL a desirable candidate to be used as raw material for energy storage devices. For solution phase, in presence of external hydroxylic environment, PCL reacts with external water molecules through weak IerHB and creates different hydrated PCL/(H2O)n complexes by creating water bridge with number of water molecules from 1 to n. An increasing number of water molecules helps to form stronger hydrated complex by separation of charges by lowering the transferring energy barrier.

Solution-Processed Free-Standing Ultrathin Two-Dimensional PbS Nanocrystals with Efficient and Highly Stable Dielectric Properties

Two-dimensional (2D) materials with downscaled thicknesses are the quest of the electronics industry because of their immense potential in modern microelectronics. Despite the discovery of several novel 2D materials, the flexible design of high-performance free-standing ultrathin 2D dielectric nanocrystals (NCs) with a large planar morphology remains the most challenging task. We develop a method for synthesizing high-quality free-standing ultrathin 2D NCs of PbS with a well-defined large rectangular morphology with a thickness of ∼2 nm. The lateral size can be tuned up to a few hundred nanometers by changing only the reaction annealing time. Microscopic and spectroscopic analyses at different stages of the reaction reveal formation of 2D NCs by a continuous growth mechanism. The 2D NCs exhibit a nearly temperature and frequency independent high dielectric constant (>13.4) with a small dielectric loss (0.0006 at 20 K and <0.06 at 350 K for 100 kHz) over broad temperature and frequency ranges. Low-frequenc...

Pb(ZrTi)0.98Mn0.02O3 weight ratio effects on the properties of Pb(ZrTi)0.98Mn0.02O3/P(VDF-TrFE) composite film and infrared detectors

The effect of Pb(ZrTi)0.98Mn0.02O3 (PZTM) weight ratio on the properties of PZTM/P(VDF-TrFE) pyroelectric composites and devices was reported in this paper. Infrared devices were fabricated using PZTM/P(VDF-TrFE) composite films with different weight ratio. The pyroelectric coefficient, the dielectric properties and the infrared absorptivity of the composite materials have been measured. It was found that the pyroelectric constant of the composite decreased as PZTM weight increased. In contrast, the dielectric permittivity increased as PZTM weight increased. Especially, the composite with 0.41 PZTM weight ratio showed the smallest dielectric loss and largest infrared absorptivity. The properties of the detectors fabricated using the composite materials with different PZTM weight ratio have been further tested. It was found that the infrared irradiation absorptivity showed great impact on the performance of the devices other than the pyroelectric coefficient and dielectric permittivity.

Piezoelectric and Dielectric Properties of Multilayered BaTiO3/(Ba,Ca)TiO3/CaTiO3 Thin Films.

Highly oriented multilayered BaTiO3-(Ba,Ca)TiO3-CaTiO3 thin films were fabricated on Nb-doped (001) SrTiO3 (Nb:STO) substrates by pulsed laser deposition. The configurations of multilayered BaTiO3-(Ba,Ca)TiO3-CaTiO3 thin films are designed with the thickness ratio of 1:1:1 and 2:1:1 and total thickness ∼300 nm. Microstructural characterization by X-ray diffraction indicates that the as-deposited thin films are highly c-axis oriented and large in-plane strain is determined in BaTiO3 and CaTiO3 layers. Piezoresponse force microscopy (PFM) studies reveal an intense in-plane polarization component, whereas the out-of-plane shows inferior phase contrast. The optimized combination is found to be the BaTiO3-(Ba0.85Ca0.15)TiO3-CaTiO3 structure with combination ratio 2:1:1, which displays the largest domain switching amplitude under DC electric field, the largest room-temperature dielectric constant ∼646, a small dielectric loss of 0.03, and the largest dielectric tunability of ∼50% at 400 kV/cm. These results suggest that the enhanced dielectric and tunability performance are greatly associated with the large in-plane polarization component and domain switching.

In situ preparation of high quality BaTiO3 dielectric films on Si at 350–500 °C

Reducing thermal budget of functional layers grown on Si substrates has become a necessity for their integration into contemporary manufacturing technology of microelectronics. The work presented here exemplifies one of such efforts by preparing barium titanate (BaTiO3 or BTO) films at temperatures as low as 350 °C on Si substrates via a CMOS-compatible RF-magnetron sputtering process. In this study, X-ray diffraction (XRD) results reveal that use of LaNiO3 (LNO) buffer layer successfully induces BaTiO3 film’s transition from polycrystalline to highly c-axis oriented tetragonal in low temperature range. Moreover, encouraged by BaTiO3 films prepared at 500 °C that shows a nearly uniform (00l) orientation with excellent ferroelectric properties (Pr ~ 2.6 μC/cm2, Ec ~ 100 kV/cm, d33 ~ 150 pm/V), we further push the deposition temperature down to 350 °C. While showing reduced crystallinity, these lower temperature films still possess good dielectric properties which are characterized by a stable dielectric constant of 110 ± 5 and a small dielectric loss between 0.7 and 3 % in the frequency range of [1 kHz, 2 MHz]. We believe the finding of high quality BaTiO3 films achievable at 350 °C is meaningful in that it paves the road for BaTiO3’s real application in Si based CMOS technology.

Effects of ultrasonication and conventional mechanical homogenization processes on the structures and dielectric properties of BaTiO3 ceramics

The effects of the homogenization process on the structures and dielectric properties of pure and Nb-doped BaTiO3 ceramics have been investigated using an ultrasonic homogenization and conventional mechanical methods. The reagents were homogenized using an ultrasonic processor with high-intensity ultrasonic waves and using a compact mixer-shaker. The components and crystal types of the powders were determined by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The complex permittivity (ε′, ε″) and AC conductivity (σ′) of the samples were analyzed in a wide frequency range of 20Hz to 2MHz at room temperature. The structures and dielectric properties of pure and Nb-doped BaTiO3 ceramics strongly depend on the homogenization process in a solid-state reaction method. Using an ultrasonic processor with high-intensity ultrasonic waves based on acoustic cavitation phenomena can make a significant improvement in producing high-purity BaTiO3 ceramics without carbonate impurities with a small dielectric loss.

Strain Engineered CaBi2Nb2O9 Thin Films with Enhanced Electrical Properties.

In this work, strain engineered polycrystalline thin films (∼250 nm) of bismuth layer-structured ferroelectric (BLSF) CaBi2Nb2O9 (CBNO) were prepared by using a radio frequency (RF) magnetron sputtering technique. XRD analysis revealed that the films were (200)/(020) and (00l) textured with a large in-plane tensile stress. Cross-sectional TEM analyses confirmed the bismuth layered-structure, as well as crystalline orientations and a strain-controlled growth mode of the grains. Result of a quantitative XPS analysis revealed that the composition of the film is close to the chemical stoichiometry. Excellent electrical properties were achieved in the CBNO films, including a high dielectric constant (∼280 @5 kHz), a small dielectric loss (tgδ ≤ 1.6% up to an applied electric field of ∼1200 kV/cm) and a large polarization (Pr ≈ 14 μC/cm(2) @ 1 kHz).

Growth and Characterization of Pure and Metal Halides Doped Acetoacetanilide Single Crystals

The focus of this paper is on growing quality single crystals of pure acetoacetanilide and NaCl and KCl doped acetoacetanilide which possess better nonlinear optical properties. Solvent evaporation technique was used for growing these crystals. The solution and operation temperature used was ethanol and 30 °C respectively. Single crystal X-ray analysis was used to determine the grown crystals lattice parameters. The crystalline perfection was identified by the well-defined sharp peak in the pattern of powder X-ray diffraction. The presence of dopants and transparency of the doped crystals are confirmed by the ICP AES spectrum and the UV–Vis NIR spectral study respectively. This emphasizes the AA crystal host lattice of metal ion inclusion. The optical band gap of the pure AA, NaCl doped AA (AANC) and KCl doped (AAKC) crystals was found to be 5.09, 5.48 and 5.74 eV respectively. Kurtz powder technique assessed the second-order non-linearity of the grown crystal. The pure and doped AA second harmonic generation efficiency was projected to be larger than KDP by a factor of 4. The dielectric measurement reveals that there is a small dielectric constant and dielectric loss at greater frequencies for both the types of AA. Photo conducting nature was confirmed by the photoconductivity studies of pure and doped AA.

Polypropylene/Polyaniline Nanofiber/Reduced Graphene Oxide Nanocomposite with Enhanced Electrical, Dielectric, and Ferroelectric Properties for a High Energy Density Capacitor.

This work demonstrates a ternary nanocomposite system, composed of polypropylene (PP), redoped PANI (r-PANI) nanofibers, and reduced graphene oxides (RGOs), for use in a high energy density capacitor. r-PANI nanofibers were fabricated by the combination methods of chemical oxidation polymerization and secondary doping processes, resulting in higher conductivity (σ≈156 S cm(-1)) than that of the primarily doped PANI nanofibers (σ≈16 S cm(-1)). RGO sheets with high electron mobility and thermal stability can enhance the conductivity of r-PANI/RGO (σ≈220 S cm(-1)) and thermal stability of PP matrix. These findings could be extended to combine the advantages of r-PANI nanofibers and RGO sheets for developing an efficient means of preparing PP/r-PANI/RGO nanocomposite. When the r-PANI/RGO cofillers (10 vol %) were added to PP matrix, the resulting PP/r-PANI/RGO nanocomposite exhibited high dielectric constant (ε'≈51.8) with small dielectric loss (ε″≈9.3×10(-3)). Furthermore, the PP/r-PANI/RGO nanocomposite was used for an energy-harvesting device, which demonstrated high energy density (Ue≈12.6 J cm(-3)) and breakdown strength (E≈5.86×10(3) kV cm(-1)).

Dielectric Properties of Y&lt;sub&gt;2&lt;/sub&gt;NiMnO&lt;sub&gt;6&lt;/sub&gt; Ceramics at Various Sintering Times and Temperatures

Dielectric properties of hydrothermally decomposed Y2NiMnO6 ceramics prepared under several sintering conditions were investigated at room temperature. As the results, dielectric constants at 200 Hz were found about 928 and 23x103 for samples sintered at 1000 and 1400 oC, respectively. The dielectric permittivity for samples sintered at 1400 oC for different sintering times from 6 to 24 hours have yielded the best dielectric permittivity value of 104. On the other hand, low sintering temperature had resulted in smaller dielectric loss in comparison to larger dielectric loss generally found in the ceramics with high sintering temperature.

Solid State Sintering and Microstructural Evolution on Wide Frequency Range Dielectric Responses of Mechanically Activated CaTiO&lt;sub&gt;3&lt;/sub&gt; Ceramics

The CaTiO3 samples were prepared by high-energy ball milling process followed by sintering process from 1040 to 1200°C. X-ray diffraction (XRD), microstructural analysis, and dielectric properties over a wide range of frequency varying from 0.01 Hz to 1 GHz at room temperature were investigated. The formation of a single phase CaTiO3 with orthorhombic structure was achieved at 1120°C and above. From a morphological point of view, sintering temperature promoted grain growth. Dielectric properties in the frequency range 0.01 Hz - 1 MHz revealed a relaxation-type process. Interfacial phenomena were the possible physical mechanisms that gave rise to these relaxation-type plots. Extending the frequencies above ~1 MHz yielded a frequency-independent characteristic of dielectric constant (ε'). These turned out to the relatively small dielectric loss (tan δ) values. The origin of the dielectric responses in the frequency range 1 MHz - 1 GHz was attributed to the domination of dipolar polarization. The grain size effect in sintered CaTiO3 samples was prominent, notably in dielectric responses above ~1 MHz. Increase in sintering temperature remarkably led to an enhancement in dielectric constant values and reduction in dielectric loss values. Therefore, a significant correlation existed between microstructural features and dielectric properties.