TiO3 Ceramics Research Articles

Characterization of dielectric and piezoelectric responses in 0.76(Na0.5Bi0.5)TiO3-0.06BaTiO3-0.18(K0.5Bi0.5)TiO3 ceramics synthesized by the solid-state method

In this research, the authors explore the structural, dielectric, electrical insulating, electromechanical, and piezoelectric characteristics of ceramics that have been modified using BaTiO3 and (K0.5Bi0.5)TiO3.as key components. Specifically, they explore the composition (1-x-y)(Na0.5Bi0.5)TiO3-xBaTiO3-y(K0.5 Bi0.5)TiO3, where x (mol.%) varies between 0, 6, and NBT, and y (mol.%) varies between 0, 18, and KBT. These ceramics were fabricated using a solid-state synthesis technique. The optimized calcination temperature for achieving a pure perovskite phase was determined to be 1000 °C for a duration of 4 h. The research involves a comprehensive analysis of the composition, microstructure, electrical insulating, and electromechanical characteristics of the ceramics. Rietveld analysis of X-ray diffraction (XRD) data was employed to accurately ascertain the morphotropic phase boundary (MPB) within this material. In this paper, we discuss the impact of crystallite size on the shifts in Raman band frequencies. Sintering at 1100 °C for 4 h was found to enhance densification, with scanning electron microscopy (SEM) images illustrating a nearly uniform distribution of compact grains. Electrical insulating assessments demonstrate that each of the ceramics displays a scattered phase transition around the temperature Tm, with a diffusivity ranging from 1.4 to 1.8, and a shift of Tm towards elevated temperatures. Exceptional piezoelectric properties were observed at the morphotropic phase boundary (MPB), including a d33 value of 149 pC/N and electromechanical coupling factors kp of 0.297. These findings are attributed to the coexistence of rhombohedral and tetragonal phases, as well as precise grain size control. This research presents a novel approach to enhancing lead-free ferroelectric materials based on the composition 0.76(Na0.5Bi0.5)TiO3-0.06BaTiO3-0.18(K0.5Bi0.5)TiO3.

Leveraging the strain transfer at the interface between self-composite CoFe2O4 embedded in pre-sintered Na0.5Bi0.5TiO3 ceramics matrix for the enhancement of magnetoelectric voltage coefficient

Magnetoelectric particulate composite (100-x) NBT- xCFO(sc) (x = 5,15,25,35) were prepared from pre-sintered NBT and self-composite CFO(sc) by solid-state reaction route. XRD, SEM, and Raman studies confirm the biphasic composite formation without diffusion at the interfaces. Unsaturated ferroelectric loops and enhanced ferromagnetic properties are evidenced. ME coefficient value is enhanced to 25.1 mV cm−1 Oe in the N65SC35 composite which is the greatest among the reported values in the literature of NBT-CFO composites. The enhancement is due to the effective strain transfer at the interfaces of the composites. This is explained by a simple dimensionless quantity, degree of interface. This quantity is defined using the interface length of ferroelectric-ferromagnetic phases and the weighted average grain size which corroborates the enhancement of the ME coefficient.

Butyl rubber dispersed with low-loss Ca0.61Nd0.26TiO3 ceramics for miniaturized flexible microwave substrate applications

Ca0.61Nd0.26TiO3 (CNT)-filled butyl rubber (BR) composites were fabricated via Banbury mixing by changing the ceramic volume fraction from 0 to 0.5. The phase purity of the CNT filler was confirmed using X-ray diffraction, and the morphology of the composite samples was analyzed using scanning electron microscopy and atomic force microscopy. BR/CNT composites filled with 50 vol% filler possessed excellent dielectric properties with a dielectric constant of 11.12 and a very low dielectric loss of 0.0023 in the X-band (8–12 GHz) frequencies. Moreover, the material displayed an appreciable thermal conductivity of 0.883 W/mK, low water absorption of 0.0574 %, and an acceptable CTE of 37.08 ppm/ °C. Thus, the developed BR/CNT composites can be used for flexible microwave circuit applications that require miniaturization.

Titanium dioxide bioceramics prepared by 3D printing method and its structure effect on stem cell behavior

3D printing was widely used for the modification of bioceramic structures. Here, Bioactive titanium dioxide (TiO2) ceramics with macropore structures were prepared by controlling the pore size through 3D printing, and further obtained secondary micropores by altering the sintering temperature. The structures and in vitro bioactivity of materials were characterized, and the properties of the ceramics for osteogenic differentiation of rabbits bone marrow mesenchymal stem cells (rBMSCs) were investigated. The results showed that titanium dioxide ceramics could induce apatite formation in SBF, which indicated it is bioactive. All materials exhibited porous structures, which could promote the proliferation and osteogenic differentiation of rBMSCs. Importantly, the structure with 200 μm pore size significantly promoted the proliferation and adhesion of cells. Furthermore, more secondary micropores formed on the surface of materials with the decreased sintering temperature, which promoted cell proliferation. The pore size of 400 μm significantly upregulated the expression of osteogenesis-related genes, including Col I, ALP, Runx2, and OPN. It had the strongest osteogenic ability when sintered at 1100 °C compared to other groups. This implies that the 3D-printed TiO2 ceramics have good osteogenic properties, and the hierarchical structure consisting of macroscopic pores and secondary micropores can control it well.

Excellent temperature stability of piezoelectric properties in PbNb2O6‐based ceramics up to 450°C

AbstractDense (Pb0.92Ba0.08)Nb2O6‐xmol% MnO2 with 0.25 wt% TiO2 ceramics with a single orthorhombic phase were synthesized through a conventional solid‐state reaction method. Excellent piezoelectric performance (d33 = 90 pC/N) and low dielectric loss (tan δ = 0.5%) are achieved in Mn‐doped samples. Interestingly, the dielectric anomalies are observed in the temperature range of 300–400°C, which could be completely suppressed through Mn doping. The dielectric anomalies are associated with thermally activated domain wall motion, which could be constrained by the defect dipoles produced by Mn doping. More importantly, all samples experience about 12% performance degradation below 300°C, attributed to an accelerated aging process at elevated temperatures. After thermal aging, the samples exhibit excellent performance stability within the temperature range of 25–450°C, showing no further degradation. The results indicate that the PbNb2O6‐based ceramics are promising high‐temperature piezoelectric materials for piezoelectric devices operating at temperatures up to 450°C.

Enhanced energy storage properties of (Ba0.4Sr0.6)TiO3 ceramics with ultrahigh energy efficiency through doping of Bi0.2Sr0.7(Mg1/3Nb2/3)O3

Dielectric (Ba0.4Sr0.6)TiO3 (BST) ceramics are promising dielectric energy storage materials due to their moderate dielectric constant, low dielectric loss, and slight nonlinearity. However, their energy density is limited by their low breakdown strength (BDS). In this study, we aimed to address this limitation by incorporating various amounts of Bi0.2Sr0.7(Mg1/3Nb2/3)O3 (SBMN) into the BST matrix. The (1–x)BSTxSBMN ceramics were prepared by conventional solid-state sintering, resulting in single-phase solid solutions. Compared to pure BST ceramics, the (1–x)BST–xSBMN ceramics exhibited lower remnant polarization and significantly enhanced BDS. Furthermore, the relaxation of the ceramics enhanced with increasing doping concentration, with an efficiency of η = 94.0% achieved at x = 0.20. Among them, the breakdown field strength of 0.85BST–0.15SBMN ceramics was 597 kV cm−1, achieving a recoverable energy storage density of Wrec = 2.81 J cm−3 and an efficiency of η = 90.8% under an external electric field of 480 kV cm−1. Subsequent tests revealed that the introduction of SBMN not only increased the band gap and conduction activation energy of the material, leading to an increase in BDS, but also promoted the formation of polar nanoregions (PNRs) which contributed to boosted energy efficiency, resulting in a significant enhancement in the energy storage performance of BST ceramics.

Modified energy storage properties of lead-free Sr0.3Bi0.35Na0.335Li0.015TiO3 ceramics with La3+ substitution via the solid-state combustion technique

In this study, the influence of La3+ substitution on the phase structure, microstructure, electrical and energy storage properties of (Sr0.3Bi0.35Na0.335Li0.015)1-xLaxTiO3 (SBNLT-xLa) ceramics with x = 0–0.05, using the solid-state combustion technique, was investigated. X-ray diffraction (XRD) patterns indicated a pure perovskite structure formed, along with coexisting rhombohedral and tetragonal phases in all ceramics. The Rietveld refinement analysis showed the tetragonal phase increased while the rhombohedral phase decreased with increased La3+ content. The morphology of the SBNLT-xLa ceramics displayed polygonal grain shapes and anisotropic grain growth. Average grain sizes increased from 2.01 to 2.43 μm as x increased from 0 to 0.01 and afterwards decreased as x increased further. Both the measured density and maximum dielectric constant (ɛm) decreased from 5.48 to 5.29 g/cm3 and from 4667 to 2313, respectively, when x increased from 0 to 0.05. A decrease in the dielectric properties caused by the phase ratio shifting away from a morphotropic phase boundary (MPB) condition, poor microstructure and low density was produced with La3+ replacement. The maximum polarization (Pmax), remnant polarization (Pr) and coercive field (Ec) decreased with increased La3+ content. A decline in Pr and Ec improved the energy storage efficiency (ƞ) and energy storage loss (Wloss), resulting in enhanced energy storage properties. At x = 0.02, the ceramic showed good energy storage properties (Wtotal of 0.781 J/cm3, Wrec of 0.624 J/cm3, Wloss of 0.157 J/cm3 and ƞ of 79.8%), measured at 60 kV/cm.

Dielectric, ferroelectric, piezoelectric properties, and conduction behavior of (Bi0.5Na0.5)0.94+xBa0.06TiO3 ceramics

Dielectric, ferroelectric, piezoelectric properties, and conduction behavior of (Bi0.5Na0.5)0.94+xBa0.06TiO3 ceramics

Colossal permittivity and ferroelectric properties regulation of different kinds of doped TiO2

TiO2, a typical incipient ferroelectric material, has been extensively studied for its ferroelectric or dielectric properties, which can be achieved via donor and acceptor co-doping. However, the influence of doping ions on the performance of TiO2 remains unclear. In this study, the relationship between the properties of TiO2 and doping ions was investigated by selecting acceptors with various ionic radii. Colossal permittivity in TiO2 was achieved by doping large-ionic-radius acceptors, forming defect complexes to pin electrons and mitigate dielectric loss. For small acceptor ionic radii, donor–acceptor co-doped TiO2 exhibited ferroelectricity at room temperature. The electric dipole moment formed by the donor and acceptor readily rotated under an external electric field, resulting in ferroelectricity at room temperature. This study provides a design perspective for the selection of doping ions to achieve various properties in rutile-type TiO2 ceramics.

Enhanced energy storage and temperature-stable dielectric properties in (1-x)[(Na0.4K0.1Bi0.5)0.94Ba0.06TiO3]-xLa0.2Sr0.7TiO3 lead-free relaxor ceramics

With the continuous growth in sustainable and renewable technologies, ceramic capacitors are emerging as a promising energy storage device. Lead-free (1-x)[(Na0.4K0.1Bi0.5)0.94Ba0.06TiO3]-xLa0.2Sr0.7TiO3 (0 ≤ x ≤ 0.40) ceramics were prepared using the solid-state reaction technique for obtaining relaxor characteristics with improved energy storage density, efficiency, and temperature stability of dielectric permittivity. A high recoverable energy density (Wr) ∼ 2.39 J/cm3 with a good efficiency (η) of ∼ 75.21% was obtained for x = 0.30 composition under 220 kV/cm applied field. The specimen x = 0.30 exhibited excellent fatigue resistance during 105 cycles and good temperature stability of energy storage characteristics (Wr > 0.87 J/cm3, η > 74%) in the temperature range of 25–180 °C under 100 kV/cm. In addition, the temperature range in which the dielectric permittivity variation was less than ±15% was very wide (204 °C (63–267 °C) and 275 °C (39–314 °C) for x = 0.30 and 0.20 specimens, respectively). Significant improvements in material performance were attributed to A-site engineering, which resulted in a mixture of P4bm and R3c polar nano regions (PNRs), leading to reduced hysteresis loss and temperature-stable dielectric permittivity. Additionally, the size of PNRs ranged between 3 and 6 nm, with the P4bm phase dominating in the x = 0.30 specimen, leading to a large maximum polarization under an applied electric field. Therefore, (1-x)[(Na0.4K0.1Bi0.5)0.94Ba0.06TiO3]-xLa0.2Sr0.7TiO3 relaxor ceramics are promising for high energy density materials and electronic applications requiring high permittivity stability over a wide temperature range.

High-temperature interaction of water vapor with lithium ceramics Li2TiO3

Selection of materials for fusion reactors and, in particular, for blanket systems is one of the most important tasks that determine the development of fusion energy. Lithium ceramics Li2TiO3 is considered as prospective candidate for solid breeders of future fusion reactors' blankets. The paper presents the results of high-temperature tests of Li2TiO3 + 5 mol% TiO2 ceramics, performed under conditions of blowing with argon containing impurities of water vapor of different isotopic compositions (H2O, HDO, D2O) in the range of temperature from 100 °C to 1400 °C. The vapor–gas mixture for the experiment was prepared in a special mixing tank. The interaction of Li2TiO3 + 5 mol% TiO2 ceramics with chemically active gases and water vapors was investigated by thermogravimetry (TG), differential scanning calorimetry (DSC) and mass spectrometry (MS) methods. As a result of experiment, the dependences of the sample mass change during heating under single purge gas composition was obtained. Mass spectra that characterize the changes in the qualitative composition of the gas mixture in the reaction chamber with the investigated sample were recorded and subsequently analyzed. An isotope effect is observed during the experiment: the release of D2 gas begins significantly earlier than the release of HD gas. The observed effect appears only in the high-temperature region (above 1050 °C), which characterizes the investigated material as almost completely chemically neutral towards water vapor.

Evidence for Vogel Fulcher behavior of the 50K-relaxation in (Tm+Ta) co-doped TiO2 ceramics

There is still no consensus about the relaxation behavior of the so-called 50[Formula: see text]K-relaxation in acceptor and donor co-doped TiO2 system. Herein, the relaxation behavior of the 50[Formula: see text]K-relaxation was investigated in (Tm[Formula: see text][Formula: see text][Formula: see text]Ta) co-doped rutile TiO2 ceramics. Dielectric properties of the sample were studied in the temperature range of 2–300[Formula: see text]K under 100 frequencies in the range of 102–106[Formula: see text]Hz. The sample shows a pronounced 50[Formula: see text]K-relaxation. Various relaxation behaviors of Arrhenius, Mott’s variable range hopping, and Vogel Fulcher laws were tried to describe the relaxation. The result indisputably evidences that the 50[Formula: see text]K-relaxation follows the Vogel Fulcher law. This work provides a heuristic hint to understand the fundamental physics underlying the colossal permittivity behavior in the acceptor and donor co-doped TiO2 ceramics system.

Retrievable Hierarchically Porous Ferroelectric Ceramics for “Greening” the Piezo‐Catalysis Process

AbstractPowder‐based piezo‐catalysis, as an effective approach to degrade wastewater and produce hydrogen from water splitting, has been widely used in the field of energy conservation and pollution reduction. However, these hard‐to‐recycle powders pose a challenge of secondary pollution in the environment. As a result, this paper provides an alternative strategy based on the manufacture of porous ceramics as a green chemistry approach to replace ferroelectric powders currently used in traditional piezo‐catalysis. The piezo‐catalytic properties of Ba0.75Sr0.25TiO3 (BST) ceramics prepared using freeze casting and direct ink writing techniques are investigated in detail. The positive effect of introducing micro‐ and macro‐pores is explored and discovered, where a BST ceramic with hierarchical pore channels is prepared by a combination of direct ink writing and freeze casting and exhibts the highest first‐order kinetic rate constant per mass of catalysts, k, of up to 2.91 min−1 kg−1 compared to bulk BST ceramics. This study therefore provides the first report for the benefits of hierarchical porous ferroelectric ceramics used in water splitting, with an average H2 production rate reaching 848.88 nmol g−1 h−1.

Effects of Zr4+ and Hf4+ substitution on the structure and dielectric response of Ba4Sm9.33Ti18O54 ceramics

Microwave dielectric ceramics with high relative permittivity (εr) are commonly used for the miniaturation of microwave devices. The dielectric loss mechanism of microwave dielectric ceramics, as well as the property modification, has been a concerned topic among scholars. Herein, the lattice structure, defects, and broadband dielectric response of Zr4+ and Hf4+ substituted Ba4Sm9.33Ti18O54 (BST) ceramics are systematically examined. The negative temperature coefficient of resonant frequency (τf) of BST ceramics can be tuned to near zero via ion substitution, owing to the Sm2Ti2O7 second phase with a large positive τf. Optimal microwave dielectric properties of εr = 81.3, Q × f = 10,800 GHz, and τf = −4.6 ppm/°C are achieved. The lattice vibration behavior and defect concentration are analyzed by Raman spectra and thermally stimulated depolarization currents (TSDC), respectively. The increasing volume of the unit cell and TiO6 octahedra, which is because of the large-radius substitution ions, leads to an increase in lattice vibration damping factor and the generation of more oxygen vacancies (VO∙∙). Therefore, the dielectric losses in the microwave and terahertz (THz) bands increase after substitution. Meanwhile, the low-frequency dielectric losses at high temperatures also increase due to the weak restraint of carriers by the lattice. The broadband loss mechanism of Zr4+ and Hf4+ substituted BST ceramics related to lattice vibration and defects might be referenced for developing low-loss dielectric ceramics.

Enhancing grain boundary contributions to improve the dielectric properties of (In0.5Nb0.5)0.05Ti0.95O2 ceramics by Bi aided sintering

The internal barrier layer capacitance effect substantially contributes to the colossal permittivity in In and Nb co-doped TiO2 (INTO) ceramics. Therefore, enhancing grain boundary density and ceramic compactness can efficaciously reduce their low-frequency dielectric loss. In this investigation, Bi2O3 addition was utilized to aid sintering and refine grains for INTO ceramics. The results reveal that Bi-doped INTO ceramics, in contrast to their undoped counterparts, exhibit a more refined and compact grain structure with a significant increase in the quantity of grain boundaries. Moreover, a noticeable reduction in low-frequency dielectric loss from above 0.1 to below 0.05 and enhanced frequency stability of permittivity from below 10 Hz to approximately 10 kHz were observed, along with a decrease in the sintering temperature to 1300 °C. In comparison to undoped INTO ceramics, Bi doping also enhances the withstand voltage capability by a factor of 1.5–4 for Bi-doped INTO ceramics. However, as the sintering temperature of Bi-doped INTO ceramics increases and the grain size enlarges, their breakdown voltage gradually decreases, but the non-linear coefficient of current-voltage characteristics progressively increases. Analysis of complex impedance spectra confirms that the increased grain boundary density and resistance in Bi-doped INTO ceramics is the primary factor for the enhanced dielectric properties and withstand voltage capability.

Ilmenite-type structure and pervoskite structure mix-phase ceramics at microwave frequency

ABSTRACT The impact of CuB2O4 additive used as a sintering aid on the microstructures and microwave dielectric characteristics of mixed phase (Mg0.95Zn0.05)Co0.05TiO3-Ca0.6(La0.9Y0.1)0.2667TiO3 ceramics was investigated. CuB2O4 additives can effectively lower the densification temperature of (Mg0.95Zn0.05)Co0.05TiO3-Ca0.6(La0.9Y0.1)0.2667TiO3 from 1450°C to the range of 1050°C ~ 1175°C. Doping CuB2O4 (0.25 ~ 2 wt%) in 0.875(Mg0.95Zn0.05)Co0.05TiO3-0.125Ca0.6(La0.9Y0.1)0.2667TiO3 ceramics can substantially enhance their microwave dielectric properties and density. With the addition of 1% and 0.25% CuB2O4, Q × f values of 43,000 GHz and 7700 GHz were obtained at 1050–1175°C, respectively. Different additions of CuB2O4 have a significant effect on the Q × f value. Temperature coefficient of resonant frequency of 0.875(Mg0.95Zn0.05)Co0.05TiO3-0.125Ca0.6(La0.9Y0.1)0.2667TiO3 (0.875MZCT–0.125CLYT) varied from 16 to 30.9 ppm/°C when adding different CuB2O4 (0.25 ~ 2 wt%).

High resistivity under colossal permittivity SrTiO3 based ceramic via controlling ion diffusion

High-performance Sr0.99La0.01TiO3 ceramics were synthesized using a conventional solid-phase method, and Sr0.99La0.01TiO3 percolated (SLT10-P) samples with excellent resistivity were obtained by coating with an oxidant and heat treatment. In this work, simultaneous excellent dielectric properties (16667 of dielectric permittivity, 0.016 of loss tangent at 1 kHz) and high resistivity (1.44 × 1011 Ω·cm at DC100V) was achieved in SLT10-P ceramics at room temperature by modulating the duration of thermal treatment. X-ray Diffraction and scanning electron microscope analyses proved the diffusion of the oxidant in the grains and grain boundaries during the heat treatment. The increase in grain boundary resistance is mainly due to the fact that the insulating layer formed by the oxide ions entering the grain boundary hinders the long-range movement of electrons. In addition, the diffusion of oxygen from the air into the ceramic during the heat treatment process also contributes to the insulation of grain boundaries.

Effect of rare earth oxides on the energy storage performance of Sr0.7Bi0.2TiO3 ceramics

In this study, Sr0.7Bi0.2TiO3 (SBT) ceramics doped with Y2O3, Dy2O3 and Gd2O3 rare earth oxides were designed and prepared by the conventional solid-state reaction method. The results show that all ceramics exhibit typical relaxor ferroelectric behavior, and the breakdown strength (BDS) of SBT ceramics is improved. Among them, Sr0.7Bi0.15Y0.05TiO3 ceramics demonstrate excellent energy storage performance, with a high recoverable energy density (Wrec ) of 2.4 J/cm3 and an efficiency (η) of 88.1% under 290 kV/cm. Furthermore, Y2O3-doped SBT ceramics exhibit a rapid discharge speed of 0.05 µs and a high power density (PD ) of 144.1 MW/cm3 under 300 kV/cm in charge-discharge tests. These characteristics have significant potential in pulse power applications.

Giant dielectric response and relaxation behavior of Bi3+/W6+ co-doped TiO2 ceramics.

With the rapid development of electronic information technology, dielectric ceramics are widely used in the field of passive devices such as multi-layer ceramic capacitors. In this paper, (Bi2/3W1/3)xTi1-xO2 (BWTOx) ceramics with superior dielectric properties have been prepared by using a traditional solid-state method. Remarkably, at a (Bi2/3W1/3)4+ doping level of 0.01, a (Bi2/3W1/3)0.01Ti0.99O2 ceramic achieved a giant dielectric permittivity of ∼1.5 × 104 and a low loss tangent of ∼0.07 at 1 kHz, as well as a good temperature independence, which could satisfy the operating temperature standards for X9R capacitors. The abnormal dielectric relaxation in the low temperature region can be explained by the interface polarization. Data based on the complex impedance spectroscopy and X-ray photoemission spectroscopy results indicate that the colossal permittivity of BWTOx ceramics is mainly ascribed to the internal barrier layer capacitance effect. The findings of this work could provide valuable insights for achieving large dielectric constants and good temperature stability simultaneously in BWTOx and other related electronic ceramic materials.

Synthesize and Characterization of Crystalline Structure and Phase Transition Temperature of Ce Substituted Ba- TiO3 Ceramics

Characterization and synthesize of Ba1-xCexTiO3 (x=0.01mol.) annealed at three different temperatures (1100oC, 1200 oC, 1300 oC) have been studied. For preparing powder of (x = 0.01 moles), Sol- Gel synthesis was carried out according to the stoichiometric conditions. The powder obtained palletized at 1.5 ton /mm2 pressure into a 10 mm dia. Pellet using PVA (polyvinyl alcohol) as binder. The pellets were then annealed at 1100oC for 1 hour. Then silver paste was applied on pellet by fully coating the one side and applying a single dot on other side, for making the pellet as capacitor. The XRD pattern reveals that the lattice parameter increases with the Ce doping and c/a ratio decreased which shows that tetragonality decreases. In all investigated samples it is assumed that the phase transition analysis, after doping Ce in BaTiO3 the Curie temperature decreases.