Temperature Dependence Of Dielectric Permittivity Research Articles

Investigate the effect of co-doping on the grain size and diffuse phase transition of barium titanate ceramics

An investigation examined the impact of co-doping BaTiO3 ceramics with La3+ and Nd3+ on their microstructural, dielectric, and phase transition properties. The synthesis of BaTiO3 with co-doping of La3+ and Nd3+, using the general formula Ba1-x(La1/3, Nd1/3)xTiO3 (BLNdTx) with varying concentrations of x (0%, 2%, 4%, and 8%), is achieved by the solid-state reaction technique. A temperature-dependent dielectric permittivity investigation was conducted at four distinct frequencies (1 kHz, 10 kHz, 100 kHz, 500 kHz, and 1 MHz) within the 30–200 °C temperature range. The findings indicate that the samples show a diffuse phase transition and a noticeable divergence from the typical Curie-Weiss equation. The diffuseness parameters γ for phase transition rose from 1.15 to 1.75 as x grew from 0 to 8%, respectively. The concurrent impact of surface phenomena, mechanical stress phenomena, and the external effect of grain boundaries might explain the substantial size reduction. An in-depth understanding of the grain size effect and its underlying mechanism would be advantageous for advancing and practically using BaTiO3-based ceramics and other ferroelectrics.

An investigation of the structure property relation of Na2MnWO6 for device application

This communication delves into the structural, microstructural, dielectric, impedance, modulus, and optical properties of the double-perovskite ceramic Na2MnWO6. Our X-ray diffraction study revealed a multiphase crystal structure in this ceramic, a result of high-temperature mixed-oxide synthesis. Morphological studies indicated a nearly uniform grain scattering and distribution with minimal spaces. The Maxwell-Wagner model, by addressing alternative polarisation mechanisms, studied the frequency-dependent dielectric properties. Our study of temperature-dependent dielectric permittivity identified a ferroelectric to paraelectric phase transition dielectric aberration. The material’s NTCR characteristic was determined using impedance analysis. Jonscher’s power law showed that the conduction mechanism follows the overlapping of large polaron tunnelling and correlated barrier hopping models, establishing the link between conductivity and frequency. Relaxation and conduction activation energies support electron hopping. UV spectroscopy revealed a band gap of 4.01 eV, and temperature-dependent resistance studies suggest a potential use in thermistors with due parameters. These findings significantly enhance our understanding of NMWO, paving the way for its potential uses in electronics and optics, owing to its unique structural, electrical, and optical features.

Relaxor-like behavior of the dielectric response of dense ferroelectric composites

We study experimentally and theoretically the influence of size effects and structural factors on the dielectric and ferroelectric properties of the dense ferroelectric composites. The composites have the form of the tape-casted films with 28 vol% of nanosized or submicron BaTiO3 particles dispersed in the polyvinyl butyral. We measured and analyzed the temperature dependences of the capacitance and dielectric losses in the temperature range (−200 – +200)oC and frequency range (102–105) Hz. The nonmonotonic temperature dependences of dielectric permittivity of the studied composite films have a wide plateau-like maxima located between 80oС and 160oС, in contrast to the relatively sharp maximum near the Curie temperature (∼124oC) observed in the fine-grained and coarse-grained ceramics, sintered from the same nanosized or submicron BaTiO3 particles at 1250oC. The shift of the dielectric permittivity and losses maxima (in more than 40oC) and their strong frequency dispersion do not agree with the behavior expected for the systems with a weak interaction between ferroelectric particles and a polymeric matrix. In contrast, we reveal the relaxor-like behavior of the composite dielectric response. To explain the observed results, we propose the analytical model, which considers the strong dipole-dipole cross-interaction of the BaTiO3 particles in the dense nanocomposite. The analytical model is corroborated by the structural studies of the BaTiO3 nanosized and submicron particles by X-ray phase analysis and static 137Ba NMR spectra, as well as by the finite element modelling of the composite polar properties, which confirms the strong cross-interactions between the dipole moments of single-domain nanoparticles and/or between the domain walls of different submicron polydomain particles.The obtained results may be useful for development of cheap and flexible lead-free dense ferroelectric nanocomposites with relaxor-like behavior of the dielectric response, which are promising for non-volatile memory and energy-saving elements, modulators, electrical converters and piezoresistive elements.

Broad temperature range with stable permittivity and low dielectric loss in (1–2x)Na0.5Bi0.5TiO3-xNaNbO3-xGdFeO3 system

High-temperature capacitors have garnered increasing attention in current research due to the inability of commercially available capacitors to meet the evolving industry demands. In this study, a Na0.5Bi0.5TiO3 based ternary system, denoted as [(1–2x)(Na0.5Bi0.5TiO3) -x(NaNbO3) -x(GdFeO3): x=0.01–0.09], was synthesised through solid-state reaction route. The influence of NaNbO3 and GdFeO3 on phase structure, dielectric, and ferroelectric properties are investigated. A fall of polar R3c phase % from X-ray refinement studies, diminishing macroscopic polarization, increasing breakdown strength, and flattening of temperature-dependent dielectric permittivity curves are perceived with the increase of substituent concentration. Temperature stable permittivity of (1–2x)(Na0.5Bi0.5TiO3) -x(NaNbO3) -x(GdFeO3) calculated ε'r/ε'r [250℃] at 1, 10, 100, 500 kHz with 10 % tolerance. Remarkably, (Δε′/ε′250°C ≤ ± 10 %) with x = 0.07 and 0.09 showed stable permittivity in the wide temperature range of (30°C to 600°C) at 500 kHz and a minimal dielectric loss (tan δ ≤ 0.01) measured at 250°C makes it a promising candidate for high-temperature dielectric capacitor applications.

Antiferroelectricity of titanite-type oxide SrTiGeO5 and its potential for power electronics applications

Antiferroelectric materials have recently received renewed attention due to the increased demand for energy-storage ceramics and power electronics applications. This study demonstrates antiferroelectricity in a titanite-type oxide, SrTiGeO5, through direct observation of a double D-E hysteresis loop by polarization measurements. Temperature dependence of dielectric permittivity shows a cusp around 550 K, indicating a relatively high antiferroelectric phase transition temperature for SrTiGeO5. It is suggested that an electric-field-induced rise of permittivity in SrTiGeO5 has the potential for application in protective circuits of power electronics devices. The present study paves the way for the development of innovative antiferroelectric applications.

Synthesis and Characterization of the Electrical and Energy Storage Properties of New Barium Titanate - Europium Titanate Solid Solution

In the present work, the investigation of the structural, dielectric, ferroelectric and energy storage properties of polycrystalline samples of (1-x)BaTiO3 – xEuTiO3 (BT-ET) solid solution materials prepared by conventional solid-state reaction method has been carried out. X-ray diffraction analyses have revealed the formation of a single-phase tetragonal structure with the P4mm space group. Furthermore, the temperature dependence of the dielectric constants marked the presence of the following sequence of structural phase transitions, namely from rhombohedral to orthorhombic, from orthorhombic to tetragonal and from tetragonal to cubic phase transitions with the increase of temperature. A diffuse phase transition has been observed from the dielectric permittivity peak and has been analyzed using the modified Curie-Weiss law and the degree of diffuseness is found to be in the range of 1.16 - 1.76 due to the existence of different states of polarization. A phase diagram has been established based on the temperature-dependent dielectric permittivity studies. The room temperature ferroelectric properties point to a coercive field larger than that of BaTiO3 ceramics. Broad dielectric peaks associated with diffuse phase transition appear in a wide temperature range (40 - 100 °C) with the highest dielectric permittivity ε’ = 6498 found in the x = 0.05 ceramics. Moreover, an improved energy storage performance is obtained in the 0.95BaTiO3-0.05EuTiO3 ceramic with a recoverable energy density of Wrec = 0.797 J/cm3, coupled with an efficiency η = 73% at 170 kV/cm and the highest storage energy density of Wst = 1.571 J/cm3 is obtained for 0.90BaTiO3-0.10EuTiO3, which is superior to other lead-free BT-based ceramics. All these features demonstrate that the BT-ET ceramics can be widely used in energy storage applications and also in high-temperature multilayer capacitors for automotive, aerospace and related industries.

Growth, Structure, and Electrical Properties of AgNbO3 Antiferroelectric Single Crystal

AgNbO3 (AN) lead-free antiferroelectric material has attracted great attention in recent years. However, little focus has been directed toward a single crystal that can provide more basic information. In this study, we successfully grew high-quality AN single crystals, using a flux method, with dimensions of 5 × 5 × 3 mm3. A systematic investigation into the crystal structure, domain structure, and electrical properties of a [001]-oriented AN single crystal was conducted. X-ray diffraction and domain structure analysis revealed an orthorhombic phase structure at room temperature. Stripe-like 90° domains aligning parallel to the [110] direction with a thickness of approximately 10–20 μm were observed using a polarized light microscope. The temperature dependence of dielectric permittivity showed M1-M2, M2-M3, and M3-O phase transitions along with increasing temperature, but the phase transition temperatures were slightly higher than those of ceramic. The AN single crystal also exhibited double polarization-electric field (P-E) hysteresis loops, which enabled good recoverable energy-storage density and efficiency comparable to ceramic. Additionally, double P-E loops were kept stable at various temperatures and frequencies, demonstrating robust stability and confirming typical antiferroelectric characteristics. Our work provides valuable insights into understanding the fundamental antiferroelectric properties of AN-based materials.

Dielectric and FTIR Investigation of the Cholesteric Liquid Crystal with the Doping of the Polymer

AbstractThe present work investigates fluorescent polymer dispersion in the cholesteric liquid crystal (LC) as a function of temperature and concentration of polymer. The dielectric parameters of the cholesteric LC are determined by measuring capacitance and inductance with the function of the frequency and temperature. The material used for doping is a polymer‐poly[(4,4′‐hexafluoroisopropylidene) diphthalic anhydride‐alt‐3,6‐diaminoacridine hemisulfate] and it is one concentration doped in pure cholesteryl stearate. The temperature dependence of dielectric permittivity has been discussed for the pure and polymer‐doped system. In addition to this Fourier transform infra‐red (FTIR) spectroscopy has also been performed to understand the interaction between cholesteric LC and polymer molecules.

Terahertz dielectric properties of Fe3O4 thin films deposited on Si (100) substrate

Fe3O4 is considered to be a promising material for terahertz spintronic applications as well as for stealth technology. However, the optical properties of Fe3O4 in the thin film form at terahertz frequencies are not reported in literature. In this article, we present the frequency and temperature dependence of dielectric permittivity (ε 1) and optical conductivity (σ 1) of Fe3O4 films deposited on Si substrate. The σ 1 of these films show absorption peaks related to charge localization and shallow impurities. It is also observed that the Fe2O3/Fe3O4 composite films have large σ 1 and ε 1 indicating their potential use for stealth technology applications. The overall optical properties are found to depend strongly on the microstructure and defects, such as, the grain size and the presence of grain boundaries, anti-phase boundaries, strain disorder due to lattice mismatch and/or the Fe+2/Fe+3 ratio.

Magnetic and electrical transport properties of Cu0.5Ni0.5Fe2O4 ferrite synthesized by plasma arc discharge process

In this study, the plasma arc discharge process was employed to synthesize nanocrystalline Cu0.5Ni0.5Fe2O4 ferrite powders. A spinel-type ferrite structure has been formed successfully, exhibiting a saturation magnetization of 87 emu g−1 and a coercivity of 26 Oe. The investigation involved studying the frequency and temperature dependence of dielectric permittivity, dielectric loss, and DC/AC conductivity over a broad frequency range (1 kHz–1 MHz) in a temperature range of 298 K–403 K. The highest value of the dielectric contestant (4746) is observed at a frequency of 1 kHz and temperature of 313 K. A maximum in the DC conductivity is observed at 403 K, which can be ascribed to the combined effects of thermally activated hopping and an increase in the concentration of both n-type and p-type charge carriers at higher temperatures.

Temperature-dependent complex dielectric permittivity: a simple measurement strategy for liquid-phase samples

Microwaves (MWs) are an emerging technology for intensified and electrified chemical manufacturing. MW heating is intimately linked to a material’s dielectric permittivity. These properties are highly dependent on temperature and pressure, but such datasets are not readily available due to the limited accessibility of the current methodologies to process-oriented laboratories. We introduce a simple, benchtop approach for producing these datasets near the 2.45 GHz industrial, medical, and scientific (ISM) frequency for liquid samples. By building upon a previously-demonstrated bireentrant microwave measurement cavity, we introduce larger pressure- and temperature-capable vials to deduce temperature-dependent permittivity quickly and accurately for vapor pressures up to 7 bar. Our methodology is validated using literature data, demonstrating broad applicability for materials with dielectric constant ε' ranging from 1 to 100. We provide new permittivity data for water, organic solvents, and hydrochloric acid solutions. Finally, we provide simple fits to our data for easy use.

A New Relaxor Ferroelectrics Ba4SrBiTi3Nb7O30 with Tungsten Bronze Structure

This paper reports the synthesis, microstructure and electrical properties of a new Ba4SrBiTi3Nb7O30 ceramic. X-ray diffraction analysis shows that the sample crystallizes into tungsten bronze structure, and the space group is P4bm. The electrical measurement results show that Ba4SrBiTi3Nb7O30 exhibits good dielectric and ferroelectric properties. The temperature-dependent dielectric permittivity indicates that the transition temperature of the prepared Ba4SrBiTi3Nb7O30 sample is around Tm ≈ 250K. With increasing the frequency, the dielectric peak moves to a lower temperature. Below 250 K, obvious polarization current can be detected, corresponding to the formation of spontaneous ferroelectric polarization. These results indicate the relaxor ferroelectric behavior of Ba4SrBiTi3Nb7O30 ceramic.

Temperature-dependent microwave dielectric permittivity of gallium oxide: A deep potential molecular dynamics study

The microwave (MW) dielectric permittivity of gallium oxide (β-Ga2O3) fundamentally determines its interaction with an electromagnetic wave in bulk power. Yet, there is a lack of experimental data due to limitations of high-temperature MW dielectric measurements and the large uncertainty under variable-temperature conditions. Herein, we develop a deep potential (DP) based on density functional theory (DFT) results and apply deep potential molecular dynamics (DPMD) for accurately predicting temperature-dependent MW dielectric permittivity of β-Ga2O3. The predicted energies and forces by DP demonstrate excellent agreement with DFT results, and DPMD successfully simulates systems up to 1280 atoms with quantum precision over nanosecond scales. Overall, the real part of the MW dielectric permittivity decreases with rising frequency, but the dielectric loss increases. The MW dielectric permittivity gradually increases as the temperature increases, which is closely related to the reduced dielectric relaxation time and increased static and high-frequency dielectric constants. Besides, the oxygen vacancy defects significantly reduce the relaxation time; however, augmenting the defect concentration will cause a slight rise in relaxation time. The electron localization function analysis reveals that more free electrons and low localization of electrons produced by high defect concentrations facilitate the increased relaxation time. This study provides an alternative route to investigate the temperature-dependent MW permittivity of β-Ga2O3, which attains prime importance for its potential applications in RF and power electronics.

0.98[(Na(1–x)/2Smx/2Nb0.3TiO3)] + 0.02MnO2 Lead-free Ceramic System Design; An antiferroelectrics with Improved Relaxation Behavior

The sodium niobate-based ceramics 0.98[(Na(1−x)/2Smx/2Nb0.3TiO3)] + 0.02MnO2 acronymed NSmNT of different compositions (x = 0.05, 0.1, 0.11, 0.12, and 0.13) were prepared via solid-state reaction method. The prepared samples were characterized by XRD to study the phase structure of the designed systems, SEM to study the microstructure properties of the NSmNT ceramics. In addition to that LCR meter was used to measure the sample temperature-dependent dielectric permittivity, dielectric loss, and systems impedance. The results showed an increment in the dielectric breakdown strength (DBS) with increasing x content from 100 kVcm–1 to 450 kVcm–1. Similarly, the high recoverable energy density (Wrec) of 5.61 J cm–3 was obtained for x = 0.11 symbolized (NSmNT2) with an exquisite efficiency of 88%. The study also analyzed the complex impedance of the NSmNT2 ceramics system to clearly understand the dielectric behavior of the system in question. A general view of things considers the NSmNT2 ceramic system to be a reliable system for pulsed power applications.

Temperature and magnetic field controlled dielectric relaxation and magnetodielectric response in KBiFe1.9Co0.1O5 polycrystalline

Abstract Cobalt (Co) substituted brownmillerite KBiFe2O5 (KBiFe1.9Co0.1O5: KBFCO) is synthesized by conventional solid-state reaction route. Rietveld refinement of X-ray diffraction data confirms the pure phase of KBFCO and crystallizes in monoclinic structure with P2/c space group. Surface morphology reveals that the grains are randomly distributed, and the average grain size varies in the range of 1–4 μm. The energy dispersive X-ray spectroscopy confirms that the chemical constituents of KBFCO are very close to the molar (1:1:2) ratio. The temperature (10–300 K) and frequency (500 Hz–1 MHz) dependent dielectric permittivity value decreases approximately 50% in the presence of the magnetic field (1.3 T). It confirms the signature of the magnetodielectric (MD) effect in the KBFCO sample. The magnetic field (±1.3 T) variation MD loop resembles the inverse-butterfly type behavior for the system. Both MD hysteresis and strength decrease with a decrease in temperature. A noticeable suppression in the dielectric relaxation is obtained by applying a 1.3 T magnetic field in the temperature range of 250 K–300 K. The measured MD effect is observed at a high frequency (30 kHz), suggesting the intrinsic effect is dominated in the probing temperature range. Observation of similar trends in magnetic field-dependent MD and magnetic loss (ML) loop rules out the existence of magnetoresistance origin MD effect. These results confirm that KBFCO has an excellent MD response even for a small applied field and holds great interest for future device applications.

Large negative electrocaloric response induced by nanoscale phase transition in (Bi, Na)TiO3-based thin films

Electrocaloric effect (ECE) offers an efficient and environmentally friendly route for solid-state cooling. Either positive or negative ECE could exhibit a large adiabatic temperature change (ΔT). Compared to the positive electrocaloric response, the investigation of negative ECE is lagging behind, largely due to the fact that its origin is still elusive. In this work, the negative ECE behavior of conventional ferroelectric thin films, namely 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 (BNBT), was studied. A remarkable ΔT of −26.1 K was acquired near 160 °C under a moderate electric field of 875 kV/cm, attributing to the ferroelectric phase transition in the polar nanoregions from rhombohedral (R3c) to tetragonal (P4bm), as confirmed by temperature-dependent dielectric permittivity, Raman spectra, and x-ray reciprocal space mapping. The BNBT thin film presents a high electrocaloric coefficient (ΔT/ΔE) of 0.0298 K cm kV−1, transcending that of the most reported negative electrocaloric response of thin films.

Enhancement in the magneto-dielectric and ferroelectric properties of BaTiO3 – CoFe1.9Yb0.1O4 core-shell multiferroic nanocomposite

Herein we report the dielectric, ferroelectric, magnetocapacitance and energy storage density properties of CoYb0.1Fe1.9O4-BaTiO3 core-shell multiferroic nano-composite synthesized by the combination of co-precipitation and sol-gel method. The XRD spectra revealed that the ferroelectric BT phase is compatible with the magnetic YbCFO phase. Scanning Electron microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDS) and Transmission Electron Microscopy (TEM) confirmed the formation of core-shell like structure in the composite. The magnetic and ferroelectric phase preserves their basic individual properties in the core–shell form. The temperature dependence of dielectric permittivity showed a sharp phase transition from cubic to tetragonal structure of the core-shell composite at 312.726 K. Frequency dependent dielectric study shows an enhanced value of permittivity (36905.0218) along with low dielectric losses (1.354). It was found that the prepared composite exhibited moderate values of saturation magnetization (3.379 emu/g) and polarization (5.146 μC/cm2) along with low remnant polarization (1.777 μC/cm2) at room temperature. Moreover, we also observed enhanced energy storage efficiency (60%) and magneto-capacitance (5.853%) which are explained due to strong interfacial coupling and reduced leakage current, making this composite promising for multifunctional device applications.

Re-entrant transitions of locally stiff RNA chains in the presence of polycations leads to gelated architectures.

The liquid-liquid phase separation of protein and nucleic acid mixtures drives the formation of numerous membraneless compartments in cells. Temperature variation is commonly used for mapping condensate phase diagrams, which often display unique upper critical temperatures. Recent report on peptide-RNA mixtures has shown the existence of lower and upper critical solution temperatures, highlighting the importance of temperature-dependent solvent and ion-mediated forces. In the present work, we employ residue-level coarse-grained models of RNA and polycation peptide chains for simulating temperature-induced re-entrant transitions and shedding light on the role played by mobile ions, temperature-dependent dielectric permittivity, and local chain stiffness. We show that differences in bending rigidity can significantly modulate condensate topology leading to the formation of gelated or fibril like architectures. The study also finds that temperature dependence of water permittivity is generally sufficient for recapitulating experimentally observed closed loop and LCST phase diagrams of highly charged protein-RNA mixtures. However, we find that similar-looking closed-loop phase diagrams can correspond to vastly different condensate topologies.

Growth, X-ray Diffraction and Dielectric Characterization of Pb5WO8 Single Crystals in the PbO–WO3 System

Single crystals of the Pb5WO8 phase were grown in the PbO–WO3 system by crystallization of (1 – x)PbO·xWO3 (x = 0.15–0.20) mixed melts. Thermogravimetric, X-ray diffraction, and dielectric studies of the single crystals were carried out. The phase melts at 712°С with decomposition to PbO and a liquid. The Pb5WO8 crystal structure is monoclinic (space group P21/n, 293 K) with the unit cell parameters a = 7.4430(1) Å, b = 12.1156(2) Å, c = 10.6284(2) Å, β = 90.658(1)°. The Pb5WO8 structure is retained at 100 K; the minor alterations in unit cell parameters are associated only with thermal expansion. The Pb5WO8 structure has a pronounced layered character; it appears as an alternation of layers formed of WO6 octahedra and strongly distorted PbO4 and PbO5 polyhedra in the direction [010]. A detailed crystal-chemical analysis of the structure was carried out. An important role of the Pb lone pair in the formation of characteristic voids in the structure was noted. The temperature-dependent dielectric permittivity and dielectric loss tangent feature relaxation peaks associated with lead and oxygen vacancies in the structure.

Effect of Sm and Fe co-doping on structural, dielectric and magnetic properties of YCrO3 perovskite

In this report, impact of co-doping of samarium (Sm3+) and iron (Fe3+) on structural, dielectric and magnetic properties of YCrO3 compound has been investigated. Here, YCrO3 and Y1-xSmxCr1-yFeyO3 (x = 0.3, y = 0.1) compounds are synthesized successfully through sol–gel auto combustion route. The synthesized samples are characterized through X-ray diffraction (XRD), surface electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), impedance analyzer and vibrating sample magnetometer (VSM) techniques. Rietveld refinement of XRD analysis reveals that both the compounds are crystallized in distorted orthorhombic structure belongs to Pnma space group. It is observed that with co-doping of both Sm3+ and Fe3+, lattice unit cell volume increases. SEM micrograph shows that the grains are slightly elongated as compared to the undoped sample. The temperature variation of real part of dielectric permittivity (εr) and tangent loss (tan δ) are analyzed over a frequency range 40 KHz − 500 KHz at a temperature range 300 K − 523 K. The temperature dependent dielectric permittivity reveals that both εr and tan δ decrease with co-doping. Moreover, both the compounds show relaxor like ferroelectric transition. Room temperature field dependent magnetization analysis shows that maximum magnetization value increases with co-doping. The result reveals that the enhanced properties with co-doping can be useful for practical device applications.