Showing papers on "Dielectric published in 2008"
TL;DR: A general approach to EDLC design leading to the maximum energy density is suggested, which has been now proved for both solvated organic salts and solvent-free liquid electrolytes.
Abstract: The research on electrochemical double layer capacitors (EDLC), also known as supercapacitors or ultracapacitors, is quickly expanding because their power delivery performance fills the gap between dielectric capacitors and traditional batteries. However, many fundamental questions, such as the relations between the pore size of carbon electrodes, ion size of the electrolyte, and the capacitance have not yet been fully answered. We show that the pore size leading to the maximum double-layer capacitance of a TiC-derived carbon electrode in a solvent-free ethyl-methylimmidazolium-bis(trifluoro-methane-sulfonyl)imide (EMI-TFSI) ionic liquid is roughly equal to the ion size (∼0.7 nm). The capacitance values of TiC−CDC produced at 500 °C are more than 160 F/g and 85 F/cm3 at 60 °C, while standard activated carbons with larger pores and a broader pore size distribution present capacitance values lower than 100 F/g and 50 F/cm3 in ionic liquids. A significant drop in capacitance has been observed in pores that w...
1,913 citations
TL;DR: The plasmonic photocatalysis will be of use as a high performance photocatalyst in nearly all current applications but will beof particular importance for applications in locations of minimal light exposure.
Abstract: Titanium dioxide (TiO2) displays photocatalytic behavior under near-ultraviolet (UV) illumination. In another scientific field, it is well understood that the excitation of localized plasmon polaritons on the surface of silver (Ag) nanoparticles (NPs) causes a tremendous increase of the near-field amplitude at well-defined wavelengths in the near UV. The exact resonance wavelength depends on the shape and the dielectric environment of the NPs. We expected that the photocatalytic behavior of TiO2 would be greatly boosted if it gets assisted by the enhanced near-field amplitudes of localized surface plasmon (LSP). Here we show that this is true indeed. We named this new phenomenon "plasmonic photocatalysis". The key to enable plasmonic photocatalysis is to deposit TiO2 on a NP comprising an Ag core covered with a silica (SiO2) shell to prevent oxidation of Ag by direct contact with TiO2. The most appropriate diameter for Ag NPs and thickness for the SiO2 shell giving rise to LSP in the near UV were estimated from Mie scattering theory. Upon implementing a device that took these design considerations into account, the measured photocatalytic activity under near UV illumination of such a plasmonic photocatalyst, monitored by decomposition of methylene blue, was enhanced by a factor of 7. The enhancement of the photocatalytic activity increases with a decreased thickness of the SiO2 shell. The plasmonic photocatalysis will be of use as a high performance photocatalyst in nearly all current applications but will be of particular importance for applications in locations of minimal light exposure.
1,422 citations
TL;DR: In this article, a review of research work and developments in synthesis, properties and characterization of silica aerogels is presented, with particular attention paid to drying, which is a critical step in aerogel synthesis and makes the production of this material more economical and commercial.
1,074 citations
TL;DR: In this article, a gate-stable ZnO thin-film transistors (TFTs) with aluminum oxide dielectric was fabricated. But the gate-bias reliability of the TFT was not improved.
Abstract: We report on the fabrication of gate-stable ZnO thin-film transistors (TFTs) with aluminum oxide dielectric. When an off-stoichiometric AlO x was deposited at room temperature, the ZnO-TFT revealed unreliable transfer characteristics: a large drain current-gate bias (I D -V G ) hysteresis and a large amount of threshold voltage (V T ) shift under gate-bias stress. As rapid thermal annealing (RTA) in O 2 ambient was applied onto AIO X at 300°C prior to ZnO channel deposition, the gate-bias reliability of the ZnO device was improved. The RTA might cause our AlO x surface to be more stoichiometric and thus to be resistant against ZnO sputter-induced damage. When the bottom-gate ZnO-TFT was fabricated with a stoichiometric Al 2 O 3 dielectric grown by atomic layer deposition (ALD), our device showed much more stable electrical characteristics than with the sputter-deposited off-stoichiometric AlO x . Last, as an ultimate effort to improve the gate reliability, we fabricated a top-gate ZnO-TFT device adopting the same thick ALD-grown stoichiometric Al 2 O 3 as in the bottom-gate device. Our top-gate device with the Al 2 O 3 dielectric then showed no hysteresis and no V T shift after several times of gate bias sweep. We conclude that both the high quality dielectric and optimized device structure are necessary to realize electrically stable ZnO-TFTs.
996 citations
TL;DR: In this paper, the authors present a review of low temperature co-fired ceramic (LTCC) technologies for high frequency applications, which will be of immense help to researchers and technologists all over the world.
Abstract: Small, light weight and multifunctional electronic components are attracting much attention because of the rapid growth of the wireless communication systems and microwave products in the consumer electronic market. The component manufacturers are thus forced to search for new advanced integration, packaging and interconnection technologies. One solution is the low temperature cofired ceramic (LTCC) technology enabling fabrication of three-dimensional ceramic modules with low dielectric loss and embedded silver electrodes. During the past 15 years, a large number of new dielectric LTCCs for high frequency applications have been developed. About 1000 papers were published and ∼500 patents were filed in the area of LTCC and related technologies. However, the data of these several very useful materials are scattered. The main purpose of this review is to bring the data and science of these materials together, which will be of immense help to researchers and technologists all over the world. The comme...
968 citations
TL;DR: Measurements of the dielectric function in the energy range from 0.025 to 3 eV reveal that the optical dielectrics constant is 70-200% larger for the crystalline than the amorphous phases.
Abstract: The identification of materials suitable for non-volatile phase-change memory applications is driven by the need to find materials with tailored properties for different technological applications and the desire to understand the scientific basis for their unique properties. Here, we report the observation of a distinctive and characteristic feature of phase-change materials. Measurements of the dielectric function in the energy range from 0.025 to 3 eV reveal that the optical dielectric constant is 70-200% larger for the crystalline than the amorphous phases. This difference is attributed to a significant change in bonding between the two phases. The optical dielectric constant of the amorphous phases is that expected of a covalent semiconductor, whereas that of the crystalline phases is strongly enhanced by resonant bonding effects. The quantification of these is enabled by measurements of the electronic polarizability. As this bonding in the crystalline state is a unique fingerprint for phase-change materials, a simple scheme to identify and characterize potential phase-change materials emerges.
922 citations
Book•
26 Sep 2008
Abstract: Microwave dielectric materials play a key role in our global society with a wide range of applications, from terrestrial and satellite communication including software radio, GPS, and DBS TV to environmental monitoring via satellite. A small ceramic component made from a dielectric material is fundamental to the operation of filters and oscillators in several microwave systems. In microwave communications, dielectric resonator filters are used to discriminate between wanted and unwanted signal frequencies in the transmitted and received signal. When the wanted frequency is extracted and detected, it is necessary to maintain a strong signal. For clarity it is also critical that the wanted signal frequencies are not affected by seasonal temperature changes. In order to meet the specifications of current and future systems, improved or new microwave components based on dedicated dielectric materials and new designs are required. The recent progress in microwave telecommunication, satellite broadcasting and intelligent transport systems (ITS) has resulted in an increased demand for Dielectric Resonators (DRs). With the recent revolution in mobile phone and satellite communication systems using microwaves as the propagation media, the research and development in the field of device miniaturization has been a major challenge in contemporary Materials Science. In a mobile phone communication, the message is sent from a phone to the nearest base station, and then on via a series of base stations to the other phone. At the heart of each base station is the combiner/filter unit which has the job of receiving the messages, keeping them separate, amplifying the signals and sending then onto the next base station. For such a microwave circuit to work, part of it needs to resonate at the specific working frequency. The frequency determining component (resonator) used in such a high frequency device must satisfy certain criteria. The three important characteristics required for a dielectric resonator are (a) a high dielectric constant which facilitates miniaturization (b) a high quality factor (Qxf) which improves the signal-to-noise ratio, (c) a low temperature coefficient of the resonant frequency which determines the stability of the transmitted frequency.During the past 25 years scientists the world over have developed a large number of new materials (about 3000) or improved the properties of known materials. About 5000 papers have been published and more than 1000 patents filed in the area of dielectric resonators and related technologies. This book brings the data and science of these several useful materials together, which will be of immense benefit to researchers and engineers the world over. The topics covered in the book includes factors affecting the dielectric properties, measurement of dielectric properties, important low loss dielectric material systems such as perovskites, tungsten bronze type materials, materials in BaO-TiO2 system, (Zr,Sn)TiO4, alumina, rutile, AnBn-1O3n type materials, LTCC, ceramic-polymer composites etc. The book also has a data table listing all reported low loss dielectric materials with properties and references arranged in the order of increasing dielectric constant.Key Features:- collects together in one source data on all new materials used in wireless communication- includes tabulated properties of all reported low loss dielectric materials- in-depth treatment of dielectric resonator materials
855 citations
TL;DR: Electric-field-induced superconductivity in an insulator is reported by using an electric-double-layer gating in an organic electrolyte using a pristine SrTiO(3) single-crystal channel, indicating this method as promising for searching for unprecedented superconducting states.
Abstract: Increasing the carrier density of a material to the limit at which superconductivity can be induced has been a long-standing challenge. This is now realized in an insulator by using an electric-double-layer gate in an organic electrolyte. Electric field control of charge carrier density has long been a key technology to tune the physical properties of condensed matter, exploring the modern semiconductor industry. One of the big challenges is to increase the maximum attainable carrier density so that we can induce superconductivity in field-effect-transistor geometry. However, such experiments have so far been limited to modulation of the critical temperature in originally conducting samples because of dielectric breakdown1,2,3,4. Here we report electric-field-induced superconductivity in an insulator by using an electric-double-layer gating in an organic electrolyte5. Sheet carrier density was enhanced from zero to 1014 cm−2 by applying a gate voltage of up to 3.5 V to a pristine SrTiO3 single-crystal channel. A two-dimensional superconducting state emerged below a critical temperature of 0.4 K, comparable to the maximum value for chemically doped bulk crystals6, indicating this method as promising for searching for unprecedented superconducting states.
851 citations
TL;DR: In this paper, two primary types of radiation-induced charge are oxide-trapped charge and interface-trap charge, which can cause large radiationinduced threshold voltage shifts and increases in leakage currents.
Abstract: Electronic devices in space environments can contain numerous types of oxides and insulators. Ionizing radiation can induce significant charge buildup in these oxides and insulators leading to device degradation and failure. Electrons and protons in space can lead to radiation-induced total-dose effects. The two primary types of radiation-induced charge are oxide-trapped charge and interface-trap charge. These charges can cause large radiation-induced threshold voltage shifts and increases in leakage currents. Two alternate dielectrics that have been investigated for replacing silicon dioxide are hafnium oxides and reoxidized nitrided oxides (RNO). For advanced technologies, which may employ alternate dielectrics, radiation-induced voltage shifts in these insulators may be negligible. Radiation-induced charge buildup in parasitic field oxides and in SOI buried oxides can also lead to device degradation and failure. Indeed, for advanced commercial technologies, the total-dose hardness of ICs is normally dominated by radiation-induced charge buildup in either parasitic field oxides and/or SOI buried oxides. Heavy ions in space can also degrade the oxides in electronic devices through several different mechanisms including single-event gate rupture, reduction in device lifetime, and large voltage shifts in power MOSFETs.
644 citations
TL;DR: In this article, the rotational distortions of the oxygen atoms are exploited to give rise to improper ferroelectricity in superlattices with very short periods, where the ground state of the system is not purely Ferroelectric, but also primarily involves antiferrodistortive rotations.
Abstract: Ferroelectric thin films and superlattices are currently the subject of intensive research because of the interest they raise for technological applications and also because their properties are of fundamental scientific importance. Ferroelectric superlattices allow the tuning of the ferroelectric properties while maintaining perfect crystal structure and a coherent strain, even throughout relatively thick samples. This tuning is achieved in practice by adjusting both the strain, to enhance the polarization, and the composition, to interpolate between the properties of the combined compounds. Here we show that superlattices with very short periods possess a new form of interface coupling, based on rotational distortions, which gives rise to 'improper' ferroelectricity. These observations suggest an approach, based on interface engineering, to produce artificial materials with unique properties. By considering ferroelectric/paraelectric PbTiO3/SrTiO3 multilayers, we first show from first principles that the ground-state of the system is not purely ferroelectric but also primarily involves antiferrodistortive rotations of the oxygen atoms in a way compatible with improper ferroelectricity. We then demonstrate experimentally that, in contrast to pure PbTiO3 and SrTiO3 compounds, the multilayer system indeed behaves like a prototypical improper ferroelectric and exhibits a very large dielectric constant of epsilon(r) approximately 600, which is also fairly temperature-independent. This behaviour, of practical interest for technological applications, is distinct from that of normal ferroelectrics, for which the dielectric constant is typically large but strongly evolves around the phase transition temperature and also differs from that of previously known improper ferroelectrics that exhibit a temperature-independent but small dielectric constant only.
608 citations
TL;DR: In this paper, the dielectric properties of epoxy nanocomposites with insulating nano-fillers, viz., TiO2, ZnO and AI2O3 were investigated at low filler concentrations by weight.
Abstract: The dielectric properties of epoxy nanocomposites with insulating nano-fillers, viz., TiO2, ZnO and AI2O3 were investigated at low filler concentrations by weight. Epoxy nanocomposite samples with a good dispersion of nanoparticles in the epoxy matrix were prepared and experiments were performed to measure the dielectric permittivity and tan delta (400 Hz-1 MHz), dc volume resistivity and ac dielectric strength. At very low nanoparticle loadings, results demonstrate some interesting dielectric behaviors for nanocomposites and some of the electrical properties are found to be unique and advantageous for use in several existing and potential electrical systems. The nanocomposite dielectric properties are analyzed in detail with respect to different experimental parameters like frequency (for permittivity/tan delta), filler size, filler concentration and filler permittivity. In addition, epoxy microcomposites for the same systems were synthesized and their dielectric properties were compared to the results already obtained for nanocomposites. The interesting dielectric characteristics for epoxy based nanodielectric systems are attributed to the large volume fraction of interfaces in the bulk of the material and the ensuing interactions between the charged nanoparticle surface and the epoxy chains.
09 Jul 2008
TL;DR: In this article, a review of the history of dielectric theory is presented, with emphasis on the relationship to the development of molecular field concepts and the study of disordered structures, in recent decades.
Abstract: The history of this field is reviewed, with emphasis on the relationship to the development of molecular field concepts in dielectric theory, in the last century, and with emphasis on the relationship to the study of disordered structures, in recent decades. A few of the many methods for calculating effective conductivities will be presented and discussed. One of these is based on the direct macroscopic application of the Clausius‐Mossotti relationship. In that connection we emphasize the shortcomings of the commonly accepted Lorentz derivation for the internal field and restate a less well known existing alternative derivation. The symmetrical and unsymmetrical effective medium theories of Bruggeman are presented. Connection is made to transport in randomly chosen resistor networks, to percolation threshold problems, and to transport in magnetic fields in the presence of inhomogeneities. Two more specialized topics are also discussed. One of these is the variability in field effect transistor thresholds arising from the limited size of the samples in which threshold is determined by the onset of percolation. The other specialized topic: The occurrence of strong spatial inhomogeneities in fields and currents in metals, in the presence of lattice defects, even though the mean free path is large compared to the extent of the defect.
TL;DR: This work proposes a heuristic model to replace the commonly used model for an electric double-layer capacitor (EDLC) on the basis of anElectric double-cylinder capacitor for mesopores (2 {50 nm pore size), which becomes an electric wire-in-cylinders capacitor (EWCC) for micropores (< 2 nm port size).
Abstract: The unprecedented anomalous increase in capacitance of nanoporous carbon supercapacitors at pore sizes smaller than 1 nm [Science 2006, 313, 1760.] challenges the long-held presumption that pores smaller than the size of solvated electrolyte ions do not contribute to energy storage. We propose a heuristic model to replace the commonly used model for an electric double-layer capacitor (EDLC) on the basis of an electric double-cylinder capacitor (EDCC) for mesopores (2 {50 nm pore size), which becomes an electric wire-in-cylinder capacitor (EWCC) for micropores (< 2 nm pore size). Our analysis of the available experimental data in the micropore regime is confirmed by 1st principles density functional theory calculations and reveals significant curvature effects for carbon capacitance. The EDCC (and/or EWCC) model allows the supercapacitor properties to be correlated with pore size, specific surface area, Debye length, electrolyte concentration and dielectric constant, and solute ion size. The new model not only explains the experimental data, but also offers a practical direction for the optimization of the properties of carbon supercapacitors through experiments.
TL;DR: In this article, the authors demonstrate that the surface passivation of Al2O3 can be related to a satisfactory low interface defect density in combination with a strong field-effect passivation induced by a negative fixed charge density.
Abstract: Al2O3 is a versatile high-κ dielectric that has excellent surface passivation properties on crystalline Si (c-Si), which are of vital importance for devices such as light emitting diodes and high-efficiency solar cells. We demonstrate both experimentally and by simulations that the surface passivation can be related to a satisfactory low interface defect density in combination with a strong field-effect passivation induced by a negative fixed charge density Qf of up to 1013 cm−2 present in the Al2O3 film at the interface with the underlying Si substrate. The negative polarity of Qf in Al2O3 is especially beneficial for the passivation of p-type c-Si as the bulk minority carriers are shielded from the c-Si surface. As the level of field-effect passivation is shown to scale with Qf2, the high Qf in Al2O3 tolerates a higher interface defect density on c-Si compared to alternative surface passivation schemes.
TL;DR: In this paper, a combination of the specular-reflection model and a suitable nonlocal extension of measured local dielectric functions is used to predict resonance shifts as large as 10% and field-intensity reduction of an order of magnitude at interparticle distances or metal thicknesses below 2 A.
Abstract: Spatial nonlocality in the optical response of noble metals is shown to produce significant blue shift and near-field quenching of plasmons in nanoparticle dimers, nanoshells, and thin metal waveguides. Compared with a local description relying on the use of frequency-dependent dielectric functions, we predict resonance shifts as large as 10% and field-intensity reduction of an order of magnitude at interparticle distances or metal thicknesses below 2 A, although sizable effects are already observed for dimers separated by 2 nm. The calculation method (a combination of the specular-reflection model and a suitable nonlocal extension of measured local dielectric functions) is simple to implement and can be easily generalized to arbitrarily complex nanostructures.
TL;DR: The limiting effects of varying the thickness of a dielectric overlayer on planar double split-ring resonator (SRR) arrays are studied by terahertz time-domain spectroscopy and the bounds of resonance shifting are discussed.
Abstract: The limiting effects of varying the thickness of a dielectric overlayer on planar double split-ring resonator (SRR) arrays are studied by terahertz time-domain spectroscopy. Uniform dielectric overlayers from 100 nm to 16 µm thick are deposited onto fixed SRR arrays in order to shift the resonance frequency of the electric response. We discuss the bounds of resonance shifting and emphasize the resulting limitations for SRR-based sensing. These results are presented in the context of typical biosensing situations and are compared to previous work and other existing sensing platforms.
TL;DR: In this article, a new formulation of the field theory of dielectric solids is proposed, which does not start with Newton's laws of mechanics and Maxwell-Faraday theory of electrostatics, but produces them as consequences.
Abstract: Two difficulties have long troubled the field theory of dielectric solids. First, when two electric charges are placed inside a dielectric solid, the force between them is not a measurable quantity. Second, when a dielectric solid deforms, the true electric field and true electric displacement are not work conjugates. These difficulties are circumvented in a new formulation of the theory in this paper. Imagine that each material particle in a dielectric is attached with a weight and a battery, and prescribe a field of virtual displacement and a field of virtual voltage. Associated with the virtual work done by the weights and inertia, define the nominal stress as the conjugate to the gradient of the virtual displacement. Associated with the virtual work done by the batteries, define the nominal electric displacement as the conjugate to the gradient of virtual voltage. The approach does not start with Newton's laws of mechanics and Maxwell–Faraday theory of electrostatics, but produces them as consequences. The definitions lead to familiar and decoupled field equations. Electromechanical coupling enters the theory through material laws. In the limiting case of a fluid dielectric, the theory recovers the Maxwell stress. The approach is developed for finite deformation, and is applicable to both elastic and inelastic dielectrics. As applications of the theory, we discuss material laws for elastic dielectrics, and study infinitesimal fields superimposed upon a given field, including phenomena such as vibration, wave propagation, and bifurcation.
TL;DR: In this paper, the experimental and modeling study of bias-stress-induced threshold voltage instabilities in amorphous indium-gallium-zinc oxide thin film transistors is reported.
Abstract: The experimental and modeling study of bias-stress-induced threshold voltage instabilities in amorphous indium-gallium-zinc oxide thin film transistors is reported. Positive stress results in a positive shift in the threshold voltage, while the transfer curve hardly moves when negative stress is induced. The time evolution of threshold voltage is described by the stretched-exponential equation, and the shift is attributed to the electron injection from the channel into interface/dielectric traps. The stress amplitudes and stress temperatures are considered as important factors in threshold voltage instabilities, and the stretched-exponential equation is well fitted in various bias temperature stress conditions.
Posted Content•
TL;DR: In this paper, the specular-reflection model combined with a suitable non-local extension of measured local dielectric functions was used to design plasmon resonances in nanometer metallic elements with application to optical antennas and improved photovoltaic, light-emitting, and sensing devices.
Abstract: Non-local effects in the optical response of noble metals are shown to produce significant blueshift and near-field quenching of plasmons in nanoparticle dimers, nanoshells, and thin metal waveguides. Compared with a local description relying on the use of frequency-dependent dielectric functions, we predict resonance shifts as large as 10% and field-intensity reduction of an order of magnitude at inter-particle distances or metal thicknesses below 2 \AA. Our results are based upon the specular-reflection model combined with a suitable non-local extension of measured local dielectric functions. We present a roadmap to design plasmon resonances in nanometer metallic elements with application to optical antennas and improved photovoltaic, light-emitting, and sensing devices.
TL;DR: Experimental observations of the motion of Janus microparticles with one dielectric and one metal-coated hemisphere induced by uniform fields of frequency 100 Hz-10 kHz in NaCl solutions suggest this phenomenon may find applications in microactuators, microsensors, and microfluidic devices.
Abstract: The application of ac electric fields in aqueous suspensions of anisotropic particles leads to unbalanced liquid flows and nonlinear, induced-charge electrophoretic motion. We report experimental observations of the motion of Janus microparticles with one dielectric and one metal-coated hemisphere induced by uniform fields of frequency 100 Hz-10 kHz in NaCl solutions. The motion is perpendicular to the field axis and persists after particles are attracted to a glass wall. This phenomenon may find applications in microactuators, microsensors, and microfluidic devices.
Patent•
03 Nov 2008TL;DR: In this article, a substrate of single-crystal semiconductor material extending in a horizontal direction and a plurality of interlayer dielectric layers on the substrate are provided, each gate pattern being between a lower interlayer layer and a neighboring upper interlayer surface layer.
Abstract: In a semiconductor device, and a method of manufacturing thereof, the device includes a substrate of single-crystal semiconductor material extending in a horizontal direction and a plurality of interlayer dielectric layers on the substrate. A plurality of gate patterns are provided, each gate pattern being between a neighboring lower interlayer dielectric layer and a neighboring upper interlayer dielectric layer. A vertical channel of single-crystal semiconductor material extends in a vertical direction through the plurality of interlayer dielectric layers and the plurality of gate patterns, a gate insulating layer being between each gate pattern and the vertical channel that insulates the gate pattern from the vertical channel.
TL;DR: In this paper, the results of X-ray diffraction reveal that Ba 2+ diffuse into the Bi 0.5 Na 0.0.5 TiO 3 lattices to form a solid solution with a pure perovskite structure, and a morphotropic phase boundary (MPB) exists at 0.06.
TL;DR: In this article, the dielectric, ferroelectric and piezoelectric properties of perovskite and bismuth layered-structured Ferroelectric (BLSF) ceramics are described as superior candidates for lead-free piezolectric materials to reduce environmental damage.
Abstract: The dielectric, ferroelectric and piezoelectric properties of perovskite ferroelectric and bismuth layered-structured ferroelectric (BLSF) ceramics are described being superior candidates for lead-free piezoelectric materials to reduce environmental damage. Perovskite-type ceramics seem to be suitable for actuator and high-power applications that require a large piezoelectric constant, d33, and a high Curie temperature, Tc, or a depolarization temperature, Td (>200 °C). For BaTiO3-based solid solutions, (1-x)BaTiO3–x(Bi0.5K0.5)TiO3 (BT–BKT100x) ceramics, Tc increases with increasing amount of x. The BT–BKT20 + MnCO3 (0.1 wt %) ceramic shows a high Tc greater than 200 °C and an electromechanical coupling factor of k33 =0.35. In the case of a(Bi1/2Na1/2)TiO3–b(Bi1/2K1/2)TiO3–cBaTiO3 [BNBK (100a/100b/100c)] solid solution ceramics, d33 is 191 pC/N for BNBK (85.2/2.8/12). KNbO3 (KN)-based ceramics are also a candidate for lead-free piezoelectrics. In Mn-doped KN ceramics, a higher k33 of 0.507 is obtained for KN + MnCO3 (0.1 wt %). On the other hand, BLSF ceramics seem to be excellent candidates as piezoelectric sensors for high temperatures and ceramic resonators with a high mechanical quality factor, Qm, and a low temperature coefficient of resonance frequency, TC-f. The k33 value of the donor (Nb)-doped and grain-oriented (HF) Bi4Ti3-xNbxO12 (BITN-x) ceramic is 0.39 for x=0.08 and is able to keep the same stable value up to 350 °C. Nd(0.01) and V(0.75) co-doped Bi4Ti3O12 ceramics, BNTV(0.01, 0.75), show a relatively low TC-f. Bi3TiTaO9 (BTT)-based solid solution, Srx-1Bi4-xTi2-xTaxO9 [SBTT2(x)] (1x2), displays the high Qm value (=13500) in (p)-mode at x=1.25. For resonator applications, (Sr1-xCax)2Bi4Ti5O18 (SCBT) (0x0.5) ceramics are suitable.
TL;DR: In this paper, the authors compared electric potential wells produced by a permanent dipole moment such as that of carbonyl groups (C=0) and an induced dipole consisting of MgO nanoparticles (spherical dielectrics) under a high electric field to create a trapping site for electric charge carriers.
Abstract: Space charge accumulation in low-density polyethylene film containing a small amount of MgO nanoparticles (LDPE/MgO nanocomposite film) subjected to an electric field greater than 100 kV/mm has been studied using an improved pulsed electroacoustic (PEA) system. No marked space charge accumulation was observed in LDPE/MgO nanocomposite films. To determine the mechanism of no space charge accumulation in the LDPE/MgO nanocomposite film, we compared electric potential wells produced by a permanent dipole moment such as that of carbonyl groups (C=0) and an induced dipole consisting of MgO nanoparticles (spherical dielectrics) under a high electric field to create a trapping site for electric charge carriers. The trapping depth created by the permanent dipole moment such as that of the carbonyl groups (C=0) of chemical defects is approximately 0.45 eV. However, the potential well induced by high-permittivity dielectric nanoparticles (MgO) is about 1.5 to 5.0 eV, which is much deeper than that induced by chemical defects. The suppression of space charge formation is explained using the potential well model consisting of a dipole induced by a high-permittivity dielectric nanoparticle. We explained the suppression mechanism of charge accumulation in the LDPE/MgO film that contains deep traps.
TL;DR: In this paper, negative charge dielectric Al2O3 was applied as surface passivation layer on high-efficiency n-type silicon solar cells, achieving a confirmed conversion efficiency of 23.2% on B-doped emitters.
Abstract: In order to utilize the full potential of solar cells fabricated on n-type silicon, it is necessary to achieve an excellent passivation on B-doped emitters. Experimental studies on test structures and theoretical considerations have shown that a negatively charged dielectric layer would be ideally suited for this purpose. Thus, in this work the negative-charge dielectric Al2O3 was applied as surface passivation layer on high-efficiency n-type silicon solar cells. With this front surface passivation layer, a confirmed conversion efficiency of 23.2% was achieved. For the open-circuit voltage Voc of 703.6mV, the upper limit for the emitter saturation current density J0e, including the metalized area, has been evaluated to be 29fA∕cm2. This clearly shows that an excellent passivation of highly doped p-type c-Si can be obtained at the device level by applying Al2O3.
TL;DR: In this paper, the powder X-ray diffraction (XRD) patterns confirm the single phase spinel structure for the synthesized materials and the crystallite size was calculated from the most intense peak (3-1-1) using the Scherrer formula.
TL;DR: In this article, the depolarization temperature Td, rhombohedral-tetragonal phase transition temperature TR-T, and the temperature Tm of the maximum dielectric constant were determined from the temperature dependence of the dielectrics and piezoelectric properties.
Abstract: (1-x)(Bi0.5Na0.5)TiO3–xSrTiO3 (abbreviated as BNST100x) was prepared by a conventional ceramic fabrication process. The depolarization temperature Td, rhombohedral-tetragonal phase transition temperature TR-T, and the temperature Tm of the maximum dielectric constant were determined from the temperature dependence of the dielectric and piezoelectric properties. It is revealed that BNST100x forms a morphotropic phase boundary of rhombohedral ferroelectric and pseudocubic (tetragonal) paraelectric at x=0.26–0.28 for BNST100x, and a very large strain and normalized strain d33* of 0.29% and 488pm∕V, respectively, were obtained at x=0.28. In addition, it was clarified that the intermediate phase between TR-T (⩾Td) and Tm shows relaxor behavior.
TL;DR: In this article, the effect of Al 3+ ions on structural, Curie temperature, DC electrical resistivity and dielecltric properties are presented in nanosized cobalt ferrites.
TL;DR: In this article, the authors present the loss tangents of some common amorphous and crystalline dielectrics, measured at low temperatures (T < 100mK) with near single-photon excitation energies, using both coplanar waveguide and lumped LC resonators.
Abstract: The microwave performance of amorphous dielectric materials at very low temperatures and very low excitation strengths displays significant excess loss. Here, we present the loss tangents of some common amorphous and crystalline dielectrics, measured at low temperatures (T<100mK) with near single-photon excitation energies, E∕ℏω0∼1, using both coplanar waveguide and lumped LC resonators. The loss can be understood using a two-level state defect model. A circuit analysis of the half-wavelength resonators we used is outlined, and the energy dissipation of such a resonator on a multilayered dielectric substrate is theoretically considered.