Room Temperature Permittivity Research Articles

Enhancing SrBi₂Nb₂O₉ ceramics: The role of neodymium substitution in structural, dielectric, and ferroelectric properties

This study investigates the impact of neodymium substitution for bismuth in SrBi2Nb2O9 (SBN) ceramics, a potential lead-free alternative for ferroelectric applications. X-ray diffraction analysis reveals a decrease in lattice parameters and volume with increasing Nd content. Scanning electron microscopy examines the influence of neodymium on grain morphology, showing a transition from characteristic SBN plate-like grains to a mix of plates and micro-spheres. Dielectric properties are evaluated, showing an increase in room-temperature permittivity for Nd-doped samples compared to the undoped counterparts. Additionally, the influence of Nd doping on relaxor ferroelectric behavior is studied. The Curie temperature (Tc) increases with Nd concentration, while the temperature dependence of relaxation time weakens. Ferroelectric properties exhibit significant changes due to Nd doping. Inverse permittivity versus temperature (ϵr−1 vs. T) measurements suggest an unconventional response, potentially due to lattice strain induced by the larger ionic radius of Nd. The potential influence of doping concentration on the order of the ferroelectric transition is also explored. Overall, neodymium substitution in SBN ceramics enhances their ferroelectric properties, making them promising for advanced electronic applications.

Exploring grain size and composition effects on the functional properties of BaGexTi1-xO3 ceramics

This study investigates BaGexTi1-xO3 ceramics with varying compositions (x = 0.010, 0.018, 0.100) produced by solid-state reaction, exploring the impact of composition and sintering temperatures (1150 °C, 1200 °C, 1300 °C) on functional characteristics (low-field dielectric, tunability, ferroelectric switching). Increasing Ge amount and sintering temperatures enhances sinterability of BaGexTi1-xO3 to almost complete densification. Room temperature permittivity ranges from 1000 to 2000, with dielectric losses below 10%. For small Ge additions, the dielectric behavior and phase transitions mirror BaTiO3 ceramics. Increasing Ge addition results in a slight increase of the Curie temperature. Dielectric relaxation mechanisms involve two activation energy ranges related to oxygen vacancies and ionic conduction. Ceramics with larger grain sizes exhibit well-defined ferroelectric P(E) loops, while fine-grained ones contain extrinsic contributions. The highest tunability performances are found for the lowest Ge additions, sintered at 1150 °C, which are able to withstand the application of the highest dc field.

Enhanced dielectric and relaxation properties in Sm3+ doped KNNT ceramics

The effect of Sm3+ doping on KNNT ceramic were comprehensively investigated, specifically focusing on the phase, microstructure, and dielectric properties of (1-x)K0.5Na0.5Nb0.7Ta0.3O3·xSm2O3(x = 0–1.6 %) (denoted KNNT–xSm) ceramics. All ceramics have the perovskite structure, and doping with Sm3+ refined the ceramic grains, resulting in an increase in the room-temperature dielectric permittivity from 998 to 1568 at 100 kHz. In addition, the dielectric loss (tanδ) reduced from 0.026 to 0.019, relaxation diffusion coefficient(γ) increased from 1.35 to 1.88, and the activation energy (Ea) was 0.9–1.08eV. Thus, the dielectric and relaxation properties of KNNT ceramic can be significantly improved by Sm3+ doping.

Influence of sintering temperature on the electrical properties of SrTiO3–BaZrTiO3 ceramics for energy storage applications

The impact of the sintering temperature on the phase composition and electrical properties of 5%SrTiO3–95%BaZr0.15Ti0.85O3 (ST-BZT) ceramics fabricated by solid-state method and consolidated by two-step sintering is presented. A systematic analysis of the phase composition, microstructures, dielectric, ferroelectric, and energy storage characteristics. A di-phase SrTiO3–BaZrTiO3 composite is obtained at low sintering temperatures below 1400 °C. Increasing the sintering temperature causes a shift of the Curie temperature from 62 °C to 55 °C together with changes of permittivity values and of the ferroelectric loops, thus indicating a progressive interdiffusion process at the interfaces, together with a better densification. Remarkably, the ST-BZT composition sintered at 1500 °C exhibits characteristics of a single phase (Ba,Sr) (Zr,Ti)O3 solid solution, with high room temperature permittivity around 2950 and good ferroelectric response (saturation polarization Pmax = 12.6 μC/cm2 and remnant polarization Pr = 2.16 μC/cm2). Consequently, this composition displays a much greater recoverable energy density (Wrec = 54.5 mJ/cm3) in comparison to the ones of the di-phase ST-BZT composites and the parent phases. However, the (Sr0.05Ba0.95) (Zr0.14Ti0.86)O3 solid solution, demonstrates a lower energy efficiency (72%) in comparison to the ST-BZT di-phase composites sintered at lower temperatures, which exhibit higher energy efficiency values around 86%. In addition, the charge-discharge experiments were performed under different electric fields to disclose the difference in energy storage properties in 5%SrTiO3–95%BaZr0.15Ti0.85O3 ceramics. This suggests that the sintering strategy plays a crucial role in determining the energy efficiency of the obtained ceramics. Additionally, all the investigated ST-BZT ceramics present high energy efficiency at low-applied electric fields, suggesting their potential as candidates for energy storage capacitors operating at moderate fields.

Comparative microwave- and conventional oven-assisted hydrothermal syntheses of BaTiO3 nanoparticles for improved electroceramics

Barium titanate (BT) nanoparticles were prepared using both microwave- and conventional oven-assisted hydrothermal syntheses with varying reaction times (1 h, 3 h, and 6 h). In the case of the conventional oven-assisted hydrothermal syntheses, 16 h, 24 h, 48 h and 72 h reaction times were also studied. Structural and morphological evolution of BT particles were investigated. Microwave-assisted hydrothermal synthesis allowed for the rapid formation of nearly pure barium titanate (BT) phase in just 1 h at 200 °C. On the other hand, using a conventional oven as the heat source required at least 6 h of synthesis to achieve a similar material. When the different BT powders were pelletized and sintered at 1300 °C, ceramics with over 95 % density were obtained. The room-temperature (RT) dielectric permittivity exceeded 1750 for BT particles prepared over 6 h using both heating methods. However, a significant distinction emerged when comparing the piezoelectric coefficient (d33) values. The BT pellet obtained through the sintering of BT synthesized in the conventional oven for 6 h exhibited a notably higher d33 value, approximately 171 pC/N, as opposed to the 146 pC/N value observed in BT ceramics resulting from the microwave synthesized powders. Among the ceramic BT variations, the one derived from the best-crystallized tetragonal BT particles (CON_72h) displayed the lowest d33 value at 79 pC/N. These findings underscore the immense potential of microwave- and conventional oven-assisted hydrothermal syntheses in the sustainable production of BT nanomaterials, which can then be sintered to enable the preparation of ceramics with enhanced ferroelectric and piezoelectric properties.

Dielectric properties of Tm3+- modified K0.5Na0.5Nb0.7Ta0.3O3 ceramics

The effects of rare-earth oxide on dielectric properties of K0.5Na0.5NbO3 (KNN)-based ceramics have been rarely investigated in detail. In this work, Tm2O3 was introduced into the KNN structure for the first time to synthesize (1–x)K0.5Na0.5Nb0.7Ta0.3O3·xTm2O3 (x=0.1–1.0%) powders via a solvothermal method. The corresponding ceramics were prepared through atmospheric sintering, and their crystal phases, microstructures, and dielectric properties were systematically examined. The introduction of Tm3+ promoted the refinement of KNN grain, room-temperature dielectric permittivity increased obviously from 998 to 1990 at 100 kHz, relaxation dispersion γ increased from 1.345 to 1.569. The results of this study suggest that the dielectric properties of K0.5Na0.5Nb0.7Ta0.3O3 system can be effectively tuned via Tm3+ modification.

Role of oxygen partial pressure of synthesis environment in tuning the dielectric properties of Nd2CuTiO6

Dielectric studies were carried out on Nd2CuTiO6 samples prepared by high temperature solid-state reaction followed by annealing under different oxygen partial pressures. X-ray diffraction studies revealed that the orthorhombic (Pnma) structure of Nd2CuTiO6 is retained in all the samples. The room temperature permittivity at 100Hz was found to be about 200 in the air-annealed sample, and it increased considerably to about 3000 upon annealing in argon atmosphere. The electrical conductivity in the argon-annealed compound was found to be an order of magnitude higher than that for the air-annealed sample. On annealing in oxygen, both permittivity and electrical conductivity of the sample were found to be significantly reduced. The variation in dielectric properties could be attributed to the induction or annihilation of mixed valence state of copper and oxygen vacancies, which was supported by X-ray photoelectron and diffuse reflectance spectroscopy data. The analysis of temperature and frequency dependent conductivity and dielectric data showed that the overlapping large polaron tunnelling (OLPT) mechanism is responsible for the observed dielectric relaxations and conduction. The observed systematic dependence of properties on the oxygen partial pressure of the annealing environment suggests a simple method to tune the electrical properties of Nd2CuTiO6.

Abnormal dielectric relaxations and giant permittivity in SrTiO3 ceramic prepared by plasma activated sintering

AbstractIn this study, the dielectric properties of SrTiO3 ceramics prepared by plasma‐activated sintering (PAS) were investigated. One of the striking findings is that the material exhibits giant room temperature permittivity (k∼3.5 × 104) and low dielectric loss (∼0.05) at 1 kHz, with the permittivity exceeding that of the conventionally prepared SrTiO3（ST） ceramics (k∼300) by two orders of magnitude. The enhancement of the polarizability was caused by the high concentration of defect dipoles. In this paper, two dielectric relaxation modes of the PAS ceramics below 0°C have been mainly discussed. One dielectric relaxation mode showed higher activation energy than that of the dielectric peak in the same temperature range for the conventional SrTiO3‐based ceramics. This mode was sensitive to humidity, and the strength of this mode was associated with the oxygen vacancies concentration in the ceramics. The other mode exhibited abnormal slowing down of relaxation rate with increasing temperature, which is contrary to the typical dielectric relaxation behavior, and the anomaly persisted over a narrow temperature range. Both modes were observed at the same interface between the grain and grain boundaries.

Dielectric Relaxation and Magnetic Structure of A-Site-Ordered Perovskite Oxide Semiconductor CaCu3Fe2Ta2O12.

A new perovskite oxide semiconductor, CaCu3Fe2Ta2O12, was synthesized through a high-pressure and high-temperature approach. The compound possesses an Im3̅ space group, where it crystallizes to an A-site-ordered but B-site partial ordered quadruple perovskite structure. Spin ordering occurs around 150 K owing to the antiferromagnetic coupling between Fe3+ spins and ferromagnetic coupling between Cu2+ spins. The room-temperature dielectric permittivity of CaCu3Fe2Ta2O12 was measured to be approximately 2500 at 1 kHz. More importantly, isothermal frequency-dielectric spectroscopy demonstrates the existence of two dielectric relaxations. Debye-like relaxation is attributed to charge carriers trapped among the oxygen vacancies at low temperatures and Maxwell-Wagner polarization relaxation at high temperatures. CaCu3Fe2Ta2O12 is a new magnetic semiconductor, where A-site ordering is intercorrelated with second-order Jahn-Teller distortion. These findings offer opportunities to design novel perovskite oxides with attractive magnetic and dielectric properties.

Resource efficient exploration of ternary phase space to develop multi-layer ceramic capacitors

We demonstrate a fast, efficient combinatorial method for the optimisation of materials for multi-layer ceramic capacitors (MLCCs). Experimentally gathered permittivity-temperature profiles for nine compositions spanning a solid solution are used as input, and with series mixing rules, binary and ternary permittivity contour maps are calculated based on individual layer thicknesses. These are converted into Temperature Coefficient of Capacitance (TCC) contour maps and an algorithm is then used to identify material combinations and individual thicknesses suitable for various MLCC classifications. These facilitate targeted experimentation and allowed experimental verification of the methodology. The approach highlights that binary systems can achieve X9 (R, S T and U). classification but the addition of a third complimentary material can facilitate a tighter TCC classification (X9P) with a wider tolerance in layer thicknesses, providing a better strategy for mass production of MLCCs. The room temperature permittivity (ƐRT) for combinations with similar TCC values can also be evaluated to ensure adequate ƐRT is achieved for commercial applications.

Permittivity order modulation by intrinsic dielectric coupling

The room-temperature permittivity is reduced by one order of magnitude in a wide frequency range during each step, when the stoichiometric proportion of Cu in CaCu3Ti4O12 is decreased from 3 to 2 and then to 1. The frequency-independent reduction can be applied down to 140 K. Such an almost frequency- and temperature-independent decrease in the permittivity magnitude order suggests the existence of intrinsic dielectric coupling between binary dielectric polarization species, by which the less polaron-like 3d electrons from B-site copper ions more strongly depress the permittivity contribution from one-dimensional, anti-parallel, mutually independent, and finite length dipole chains of thermally activated off-center displacements of A-site titanium ions.

Effect of sintering temperature on dielectric properties of barium titanate ceramics and composite

The structure and dielectric properties of barium titanate ceramics samples sintered at 1100, 1150, 1200, 1250 and 1350 °C have been compared with the dielectric properties of 80 vol.% barium titanate + 20 vol.% barium ferrite composite samples sintered at 1150, 1200 and 1250 °C. It has been shown that polarization sufficient for existence of the piezoelectric effect is only achieved in barium titanate samples sintered at 1250 and 1350 °C. Furthermore the pyroelectric coefficient and reversal polarization of these samples are far higher than those of samples sintered at lower temperatures. Analysis of the sample structures has confirmed that the dielectric properties of barium titanate ceramics depend on grain size and therefore on sintering temperature. Based on the experimental results we have selected the optimum sintering temperature for 80 vol.% barium titanate + 20 vol.% barium ferrite composite to be 1250 °С. Further increase in sintering temperature to 1300 °C showed that this composite has a eutectic. The temperature dependence of the permittivity of the barium titanate / barium ferrite composite sintered at 1250 °С is similar to that of BaTiO3 ceramics samples sintered at 1350 °С. The room temperature permittivity of the composite samples also proves to be far higher than that of barium titanate ceramics samples sintered at the same temperatures. Barium ferrite addition to barium titanate increases the permittivity of the composite and also diffuses the ferroelectric phase transition and shifts the permittivity maximum temperature by 10 °C towards higher temperatures.

Beyond Substrates: Strain Engineering of Ferroelectric Membranes.

Strain engineering in perovskite oxides provides for dramatic control over material structure, phase, and properties, but is restricted by the discrete strain states produced by available high-quality substrates. Here, using the ferroelectric BaTiO3 , production of precisely strain-engineered, substrate-released nanoscale membranes is demonstrated via an epitaxial lift-off process that allows the high crystalline quality of films grown on substrates to be replicated. In turn, fine structural tuning is achieved using interlayer stress in symmetric trilayer oxide-metal/ferroelectric/oxide-metal structures fabricated from the released membranes. In devices integrated on silicon, the interlayer stress provides deterministic control of ordering temperature (from 75to 425°C) and releasing the substrate clamping is shown to dramatically impact ferroelectric switching and domain dynamics (including reducing coercive fields to <10kV cm-1 and improving switching times to <5ns for a 20µm diameter capacitor in a 100-nm-thick film). In devices integrated on flexible polymers, enhanced room-temperature dielectric permittivity with large mechanical tunability (a 90% change upon ±0.1%strain application) is demonstrated. This approach paves the way toward the fabrication of ultrafast CMOS-compatible ferroelectric memories and ultrasensitive flexible nanosensor devices, and it may also be leveraged for the stabilization of novel phases and functionalities not achievable via direct epitaxial growth.

Disorder-insensitivity of room-temperature giant permittivity in Ca4 − xCuxTi4O12 (x = 3, 2 and 1) polycrystalline ceramics

When the stoichiometric proportion of Cu in Ca4 − xCuxTi4O12 polycrystalline ceramics is decreased from 3 to 2 and then to 1, the room-temperature permittivity is reduced by one order of magnitude during each step. Ca/Cu atomic disorder is observed only in some grains of Ca3CuTi4O12 single-phase polycrystalline ceramics, and the disorder is not the origin of the giant permittivity in CaCu3Ti4O12. Quantitatively, the permittivity magnitude is related to the mole ratio of polaronlike 3d electrons from Cu ions.

Rapid synthesis of dielectric tantalum-based oxynitrides

Perovskite-type oxynitride with a general formula of ATa(O,N)3 (A = Sr, Ba) is a class of promising dielectric material due to their very high permittivity. Conventional synthesis routes for these materials always require multiple processing steps, long durations and elevated temperatures. In this study, thermodynamic calculations were employed to predict the feasible synthesis reactions, possible impurities and reasonable processing parameters. Then, ceramic powders of SrTaO2N and BaTaO2N were fabricated through direct calcination of SrCO3/BaCO3 and Ta2O5 with urea as nitrogen source by using a modified pressureless spark plasma sintering set-up. High-purity oxynitrides can be obtained within 10 min. Thermal stability, corrosion resistance and dielectric property were evaluated. The results showed that SrTaO2N was thermally stable up to 475 °C in air while that temperature for BaTaO2N was 605 °C. The oxynitrides possessed a good resistance to hot water and strong acid/alkali. BaTaO2N had a very high room-temperature relative permittivity up to 9550 with a dielectric loss down to 0.001 at 100 Hz, while the values for SrTaO2N were 3141 and 0.017 respectively. The temperature dependence of permittivity for BaTaO2N was weak at −10–200 °C. The efficient synthesis method enabled the fast preparation of the tantalum-based oxynitride materials for energy storage applications.

Nonlinear dielectric properties of BaTiO3 - Silver composites: The role of microstructure

A comprehensive insight into the structure-properties relationship of Ag–BaTiO3 composite ceramics was realized by combining modeling tools with a detailed analysis of macroscopic electrical properties in relationship with microstructural peculiarities. Di-phase Ag–BaTiO3 ceramics (0–5 vol% Ag) with room temperature permittivity values between 2740 and 7085 and low dielectric loss (tan δ < 4%) have been investigated. These composites show an enhancement of tunability from 2 for pure BaTiO3 ceramic to 4 in case of 5 vol% silver addition (at 21.6 kV/cm). The Finite Element Analysis demonstrated that the enhancement of tunability is related to the silver melting during sintering, causing peculiar microstructures, with local percolation channels in the composite’s volume.

Effect of Solution Conditions on the Properties of Sol-Gel Derived Potassium Sodium Niobate Thin Films on Platinized Sapphire Substrates.

If piezoelectric micro-devices based on K0.5Na0.5NbO3 (KNN) thin films are to achieve commercialization, it is critical to optimize the films’ performance using low-cost scalable processing conditions. Here, sol–gel derived KNN thin films are deposited using 0.2 and 0.4 M precursor solutions with 5% solely potassium excess and 20% alkali (both potassium and sodium) excess on platinized sapphire substrates with reduced thermal expansion mismatch in relation to KNN. Being then rapid thermal annealed at 750 °C for 5 min, the films revealed an identical thickness of ~340 nm but different properties. An average grain size of ~100 nm and nearly stoichiometric KNN films are obtained when using 5% potassium excess solution, while 20% alkali excess solutions give the grain size of 500–600 nm and (Na + K)/Nb ratio of 1.07–1.08 in the prepared films. Moreover, the 5% potassium excess solution films have a perovskite structure without clear preferential orientation, whereas a (100) texture appears for 20% alkali excess solutions, being particularly strong for the 0.4 M solution concentration. As a result of the grain size and (100) texturing competition, the highest room-temperature dielectric permittivity and lowest dissipation factor measured in the parallel-plate-capacitor geometry were obtained for KNN films using 0.2 M precursor solutions with 20% alkali excess. These films were also shown to possess more quadratic-like and less coercive local piezoelectric loops, compared to those from 5% potassium excess solution. Furthermore, KNN films with large (100)-textured grains prepared from 0.4 M precursor solution with 20% alkali excess were found to possess superior local piezoresponse attributed to multiscale domain microstructures.

A high dielectric permittivity and strong Ba-vacancy defects of (Ba1–xSmx)(Ti1–(x–0.01)Cox–0.01)O3 ceramic

(Ba1–xSmx)(Ti1–xCox)O3, (Ba1–xSmx)(Ti1–(x–0.01)Cox–0.01)O3 and Ba(Ti1−xCox)O3 ceramics were synthesized using a traditional solid-state based method. All series of ceramics have a structural evolution. Sm3+ as donors into Ba2+ sites could suppress the formation of hexagonal phase effectively and improve dielectric properties. Particularly a cubic ceramic (Ba1–xSmx)(Ti1–(x–0.01)Cox–0.01)O3 with x = 0.05 met the EIA Y5V specification with a higher room-temperature dielectric permittivity (ε′RT = 3955). A stronger EPR signal (g = 1.974) was attributed to ionized Ba-vacancy (VBa′′), was surprisingly observed in (Ba1–xSmx)(Ti1–(x–0.01)Cox–0.01)O3 (Ba/Ti > 1), which is extremely rare among rare-earth-doped BaTiO3 ceramics, suggests that Sm3+ ions behaved with an amphoteric nature. Interest was paid to analyze defect chemistry associated with amphoteric Sm ions and valence-variable Co ions (3+ and 4+).

High-permittivity and fine-grained (Ba1–Pr )(Ti1––/4Ce )O3 ceramics with diffuse phase transition

Abstract Fine-grained (0.8–1.1 μm) (Ba1–xPrx)(Ti1–y–x/4Cey)O3 (BPTC; x, y = 0.03–0.05) ceramics prepared by the mixed-oxide reaction route exhibit a pseudo-cubic perovskite crystal structure commensurate with a diffuse high-permittivity peak around room-temperature. Comparing to La/Ce [ J. Am. Ceram. Soc. 89 (2006), 3112–3123] or Nd/Ce [Mater. Lett. 223 (2018), 25–28] co-doped BaTiO3, BPTC ceramics with x = 0.03 and y = 0.05 exhibit a larger diffuseness parameter, γ (= 1.99), of the phase transition with temperature, thereby enhanced temperature stability; at fixed Ce content (y = 0.05), the temperature of the permittivity maximum (Tm) decreases at a rate of −29 °C/at% Pr for BPTC, this shifting rate is between that of La/Ce (−30 °C/at% La) and Nd/Ce (−27 °C/at% Nd) co-doped BaTiO3. In this study, five BPTC compositions meet Y5V specifications, in particular x = y = 0.04 ceramics exhibit the best optimized Y5V characteristics, with a high room-temperature permittivity (e′RT ∼11000) and a low dielectric loss (tan δ = 0.027). The defect chemistry of BPTC ceramics was inferred from Electron Paramagnetic Resonance in combination with ionic radii arguments.

Effect of Y substitution on magnetic and transport properties of Ba0.95La0.05Ti1−xYxO3 ceramics

Abstract Dielectric materials with giant dielectric constant are highly demanded for their many high-tech applications. While ferroelectric BaTiO3 inherently possesses polarization within it, high dielectric constant can only be obtained by structural as well as chemical modification. In this literature, we report the existence of high room temperature permittivity (≥103) in Ba0.95La0.05Ti1−xYxO3 (where x = 0.00–0.15) ceramics prepared by the pressureless conventional sintering method. Yttrium (Y) has been doped at the B site of Ba0.95La0.05TiO3 composition and their surface morphology, structural analysis, magnetic and transport properties have been investigated and discussed. XRD analysis confirms the formation of ABO3-type cubic perovskite structure of the studied compositions. The density of the prepared compositions is gradually increased with the increasing of Y content and porosity is decreased gradually. High dielectric constant and low dielectric loss with a wide range of frequency stability are observed. However, incorporation of Y in Ba0.95La0.05TiO3 gradually decreases the dielectric constant. The study of room temperature frequency dependent permeability indicates that 5% Y doped Ba0.95La0.05TiO3 possesses good magnetic properties. From the P-E loops, it is observed that Pr and Hc both are decreased with Y content. The present investigation is a fundamental step for the further improvement of the transport properties of BaTiO3 based ceramics.