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Adsorbed water promotes proton conduction in ceramics at ambient conditions prior to its evaporation, apparently leading to the positive temperature coefficient of resistivity (PTCR) effect. Using surface water-containing Cs 2 Ti 6 O 13 (1.8 mol water/mol titanate) as an example, the static conductivity (at 50 °C) of ∼10−5 S cm−1 is one thousand times that at 200 °C due to the enhanced proton conduction. At 50–150 °C, the conductivity decreases by 4 orders of magnitude because water evaporation decreases the number of charge carriers. At 150–400 °C, the conduction in water-free Cs 2 Ti 6 O 13 is thermal-activated with the apparent activation energy E a ∼58–72 kJ mol−1, depending on the formalisms. We show clearly that an endothermic DSC peak (water evaporation) in Cs 2 Ti 6 O 13 coincides with all eight presentations of AC properties examined. Similar correlations are obtained from the TG/DTG curves in Cs 2 Ti 5 O 11 ·H 2 O containing mostly intercalated water. The correlation between thermal analyses and AC properties points out that water molecules essentially contribute to the charge transport at ambient conditions of layered alkali titanates. This scenario might be potentially extended to other humidity-sensitive ceramics. [Display omitted] • Water-induced PTCR effect and Arrhenius-like process are respectively observed in the presence/absence of surface water. • The endothermic water loss peak (DSC) coincides with all representations of AC properties. • Activation energies of conduction from different formalisims were quickly obtained in a single measurement. [ABSTRACT FROM AUTHOR]

The primary goal of this study is to elucidate the structural and electrical characteristics, alongside potential applications, of ceramic-polymeric composites. These composites are achieved by incorporating lithium-lanthanum titanates (Li 3x La 2/3−x TiO 3 - LLTO) into a polyvinyl alcohol polymeric matrix (PVA). The synthesis of lithium-lanthanum titanates occurred through high-energy ball milling method. Then, three types of composites were produced using the solvent casting method: a sample of pure Poly (vinyl alcohol) polymer (PVA), a second PVA composite with the addition of La 0 · 59 Li 0 · 24 TiO 3 (Li-0.24) and a third sample with La0· 56 Li 0 · 33 TiO 3 (Li-0.33). SEM and AFM analyzes revealed notable changes in the morphology and 3D spatial patterns of the films upon incorporating lithium-lanthanum titanates into the PVA matrix. The PVA film presents a topography featuring a more evenly distributed range of topographic heights, indicating a smoother surface structure. With varying LLTO content, the morphology of the PVA composite underwent changes. The lower roughness of the PVA surface is evident from its measured average roughness value (Ra = 1.9 ± 0.5 nm). Upon incorporating LLTO, the surfaces displayed increased roughness, measuring specifically at 40.1 ± 7.3 nm (Li-0.24) and 22.7 ± 5.5 nm (Li-0.33). Notably, there was an approximately 43 % reduction in the average roughness value from Li-0.24 to Li-0.33. The analysis by Raman allowed the identification of functional groups of the PVA polymeric chain, in addition to the presence of some vibrational modes related to the structure of lithium-lanthanum titanates for the sample with the highest content of Li+ ions (Li-0.33). Finally, the sample Li-0.33 showed the lowest value of electrical resistance (67 kΩ) and of phase angle (16°), compared to the PVA (100 MΩ and 90°). These results show that the presence of the LLTO changed the insulating behavior of the PVA matrix changed and improved potential to electronic applications. [ABSTRACT FROM AUTHOR]

This work demonstrates a mechanism of heterogeneous nucleation for the synthesis of BaTiO 3 nanowires utilizing K 2 Ti 4 O 9 as template by manipulating alkalinity, temperature and reaction time. Results suggest that the synthesis of BaTiO 3 does not occur through a hydrothermal ion-exchange, instead, the predominant mechanism observed is the heterogeneous of dissolution-crystallization. The consistency of crystallographic orientation for BaTiO 3 nanowires is affected by the hydrothermal conditions. BaTiO 3 nanowires synthesized at 190 °C/0.2 M exhibit a uniform (100)/(001) crystallographic orientation, albeit not consistently along the length of the nanowires, while BaTiO 3 crystal grains no longer have the same crystallographic orientation at 190 °C/0.8 M. By investigating the reaction mechanism of BaTiO 3 , this work may have great significance for the synthesis of perovskite-type MTiO 3 (M = Ba,Ca, Sr, Pb) utilizing layered titanates. [ABSTRACT FROM AUTHOR]

High-entropy ceramics have garnered significant attention in recent years owing to their exceptional properties and structural diversity. In this work, single-phase medium/high entropy ceramics, namely (Ca 0.2 Sr 0.4 Ba 0.4)(Zr 0.5 Ti 0.5)O 3 and (Ca 0.2 Sr 0.4 Ba 0.4)(Zr 0.1 Ti 0.9)O 3 , were successfully designed and prepared utilizing Spark Plasma Sintering (SPS). A comprehensive investigation was conducted into the phase structure, microscopic morphology, dielectric properties, and thermal behavior of these ceramics. It was observed that all ceramics maintained a cubic perovskite structure (space group: Pm 3 ‾ m), and the introduction of multi-element doping rendered them more stable across a wide frequency and temperature range. Notably, (Ca 0.2 Sr 0.4 Ba 0.4)(Zr 0.5 Ti 0.5)O 3 exhibited remarkably low dielectric loss (0.0001 at 1 kHz) at room temperature, along with excellent dielectric temperature stability (25–400 °C). By reducing the zirconium concentration in (Ca 0.2 Sr 0.4 Ba 0.4)(Zr 0.1 Ti 0.9)O 3 , a slight decrease in dielectric temperature stability was observed (25–350 °C); however, it demonstrated lower thermal conductivity (0.41 W/(m·K), 1200 °C) and maintained good high-temperature stability. The discovery highlights the promising practicality of both ceramics for high-temperature dielectric applications. [ABSTRACT FROM AUTHOR]

The present study focuses on the synthesis and characterization of rare-earth titanates, specifically Re 2 TiO 5 (Re La, Nd, Sm), with a particular emphasis on their microwave dielectric properties. The factors influencing the synthesis of La 2 TiO 5 compound through the traditional solid-state method were thoroughly investigated, with a significant finding being the notable impact of moisture absorption in La 2 O 3. The impact of variations in rare-earth cation radii on the structure and dielectric properties was systematically analyzed. Re 2 TiO 5 (Re La, Nd, Sm) ceramics crystallized into an orthorhombic structure with space group Pnam, which was confirmed through Rietveld refinement. The resulting materials demonstrated exceptional microwave dielectric properties characterized by a low permittivity range of 13.72–17.39, high-quality factors ranging from 8331 to 17,795 GHz, and a significantly reduced temperature coefficient of resonance frequency (−33.2∼-12.6 ppm/°C). The correlation between microwave dielectric properties and structural characteristics (including ionic polarizability, packing fraction, and bond valence) was investigated. The exceptional potential of these rare-earth titanates lies in their ability to meet the stringent requirements for low signal transmission delay in wireless communication systems, owing to their advantageous low permittivity within the microwave frequency spectrum. [ABSTRACT FROM AUTHOR]

Iron-enriched ferroelectrics are of particular interest as piezoactive components of piezoelectric-ferrite ME ceramics. This is due to the phase composition similarity and the reduction of expected interfacial doping effects during high-temperature calcination. This idea seems attractive, but laborious due to the significantly limited number of possible piezoelectric–ferrite combinations. Therefore, there is practically no data on such systems in the literature. ME composite ceramics based on the highly efficient Fe-containing Pb(Fe 0.5 Nb 0.5) 0.935 Ti 0.065 O 3 (PFNPT) ferroelectric has been studied. (100-х) wt.% Pb(Fe 0.5 Nb 0.5) 0.935 Ti 0.065 O 3 (PFNPT) + х wt.% Ni 0.9 Co 0.1 Cu 0.1 Fe 1.9 O 4-d (NCCF) composite systems has been obtained by the solid-state method at 1050 °C, with no foreign phases. The specimens densities amounted to ∼80% of the theoretical. It has been shown that the ME conversion efficiency and other composites properties are significantly influenced by the PFNPT precursor pre-treatment method. The maximum value of the ME coefficient ΔΕ/ΔΗ = 75 mV/(cm Oe) has been observed for specimens with x = 50–60 made from PFNPT powder with the addition of Li 2 CO 3. An increase in the ME composites sintering temperature to 1150 °C leads to the formation of Pb 2 Nb 2 O 7 foreign phase with a pyrochlore structure along the grain boundaries. The ME coefficient ΔΕ/ΔΗ does not exceed 15 mV/(cm⋅Oe). There is an threefold decrease in the composites piezoelectric parameters (piezoelectric coefficients d ij , g ij), as well as in their magnetic properties (magnetizations M S , M R) due to piezophase degradation, which is presumably associated with a change in the cations distribution over A and B sublattices of the spinel structure. [ABSTRACT FROM AUTHOR]

In this work, we report on the optical properties of europium-doped SrTiO 3 , synthesized in situ via the sol-gel method as nanopowders and sintered ceramic bulks by heat treatment in vacuum. The structure and morphology of the Sr 1-3x/2 Eu x TiO 3 (x = 0.01–0.07) nanopowders and ceramics, concerning to the europium concentration, were characterized by X-ray powder diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The optical properties of as-prepared materials were also investigated. These analyses demonstrated that a temperature of 1425 °C in a vacuum of 10−4 Pa and a plateau of 4h are the optimal sintering conditions for Sr 1-3x/2 Eu x TiO 3 ceramics. Eu3+ doped SrTiO 3 ceramics exhibit visible red photoluminescence characteristics. The emission of SrTiO 3 :Eu3+ phosphor with different amounts of Eu3+, excited by 395 nm and 465 nm light, was studied. The emission spectra exhibit characteristic luminescence from 5D 0 → 7F j (j = 0, 1, 2, 3, 4) intra-4f shell Eu3+ ion transitions. The most intense transitions are 5D 0 → 7F 1 (591 nm) for pumping at 395 nm and, 5D 0 → 7F 2 (615 nm) at 465 nm. The corresponding coordinates CIE for the Eu-doped SrTiO 3 samples were calculated from the emission spectra obtained at 395 nm and 465 nm excitation wavelengths. This study demonstrates that the original protocol of materials engineering used is a simple and efficient method for manufacturing novel nanophosphors with enhanced reddish-orange emission. The as-obtained results indicated that the sol-gel synthesis combined with the sintering process in a vacuum at an appropriate temperature, plateau, could be a novel way to fabricate materials based on strontium titanate with reasonable optical properties. [ABSTRACT FROM AUTHOR]

Potassium hexatitanate whiskers (PHWs, K 2 Ti 6 O 13) are generally slender, with diameters of about 1 μm, which falls under the category of inhalable particles. Producing large-diameter rod-shaped K 2 Ti 6 O 13 is necessary to prevent the environmental and human health threats posed by inhalable fibers. We report a new synthesis approach, via spherical agglomeration, which separates the nucleation stage from the nuclei agglomeration and growth stages of the calcination process resulting in the growth of the K 2 Ti 6 O 13 micro-rods with large diameter. From thermogravimetric analysis, we deduced the critical temperature for generating K 2 Ti 6 O 13 nuclei in the melt phase to be around 800 °C; this was referred to as the nucleation stage. The absorption of K 2 O on different facets of the growing crystal nuclei was used to control the nuclei agglomerate in a subsequent step. K 2 O acted as a binding agent to agglomerate the nuclei in the melt phase and transforms the finer agglomerate nuclei into large diameter micro-rods similar to the bridging agents employed in spherical agglomeration technique. K 2 Ti 6 O 13 micro-rods with large diameters of up to 8.3 μm were produced. [ABSTRACT FROM AUTHOR]

The n -type titanate heterojunction with p -type transition metal oxides reduces the recombination effect (e−/h+) and improves the magnetic, electronic, and luminescent properties. Based on these related properties, the synthesis of nanocomposite sodium-cobalt titanate nanotube and iron oxide (Co-NaTiNT@FeO) was performed using titanium dioxide (polymorphic mixture: brookite, anatase and rutile), cobalt nitrate hexahydrate and iron oxide (FeO). The synthesized materials were characterised by X-ray diffraction (XRD), Raman and infrared (IR) spectroscopies, thermogravimetry and differential (TG-dTG), transmission electron microscopy (TEM) and scanning (SEM), X-ray photoelectron spectroscopy (XPS), adsorption/desorption of N 2 by Brunauer-Emmett-Teller (BET) method, Ultraviolet–Visible (UV–Vis) by diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and vibrating sample magnetometer (VSM). The results revealed the presence of Co2+ ions in the lamellar region of the nanotubes, in addition to verifying that there was no collapse of the nanotubes before and after the anchoring of the FeO nanoparticles. Using the XPS technique, the presence of 2.49 wt% of Fe (2p), as well as 1.55 wt% of Co (2p), was identified; these elements favoured the band gap reduction from 3.61 to 2.66 eV compared to sodium titanate nanotube (NaTiNT); in addition, they favoured the emergence of emissions associated with the red, yellow, and orange colours, described through PL. The surface area of the composite changed from 197.00 to 210.46 m2 g−1, possibly due to the homogeneous presence of anchored superparamagnetic FeO nanoparticles. Finally, the results were consistent with the proposal for the synthesis of Co-NaTiNT@FeO, which had improvements in its properties, especially its magnetic properties. [Display omitted] • TiO2 nanoparticles with phases mixture: anatase, rutile, brookite. • Direct synthesis of Co-doped Sodium Titanate Nanotubes (Co-NaTiTN) via alkaline hydrothermal method. • Superparamagnetic heterojunction of Co-NaTiNT with FeO nanoparticles. • Photocatalytic activity of heterojunction Co-NaTiNT@FeO. • Magnetic behaviour of heterojunction Co-NaTiNT@FeO. [ABSTRACT FROM AUTHOR]

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 (d 33) values. The BT pellet obtained through the sintering of BT synthesized in the conventional oven for 6 h exhibited a notably higher d 33 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 d 33 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. [ABSTRACT FROM AUTHOR]

Nowadays, there have been much consideration to develop eco-friendly advanced materials, which have many applications in the field of multiferroics, sensors, actuators, magnetically modulated transducer devices, etc. Hence, the preparation of lead-free based multifunctional materials has now become of great interest to researchers. The present study reports the synthesis and study of structural, dielectric, and multiferroics characteristics of (Bi 0.8 Nd 0.2)(Fe 0.5 Ti 0.5)O 3 material. The compound was synthesized using a conventional solid-state reaction method (calcination at 950 °C). The X-ray diffraction analysis of the compound confirms the single-phase formation with orthorhombic symmetry. The surface morphology of the material has been examined by the field emission scanning electron microscopy (FESEM) method, which shows uniform grain distribution in the microstructural image. Grains were to be found of different sizes with few voids. Energy dispersive X-ray (EDX) shows the purity of the sample with an equivalent amount of weight and atomic percentage. Dielectric and impedance analysis have been investigated in a wide range of frequencies and temperatures. Frequency-dependent ac-conductivity obeys Jonscher's universal power law. The P-E loop tracer was used to study the ferroelectric nature of the sample. Magnetic field-dependent magnetization is measured at room temperature by a vibrating sample magnetometer (VSM). The current study provides efficient, eco-friendly, and interesting results for further application purposes. [ABSTRACT FROM AUTHOR]

With great optical, catalytic and electrical characteristics, titania (TiO 2) and TiO 2 -based titanates present many potential applications in chemical and photocatalysis, solar cells, electrochemical water splitting, chemical/gas sensing, among others. Herein, we show that lepidocrocite-based titanates of low-dimensional nanotubes, NTs, nanowires, NWs, and nanoribbons, NRs, can be synthesized near ambient conditions through a bottom-up approach starting with titanium carbide, TiC, nitride, TiN, or boride, TiB 2. Successful reactions were conducted at 95 °C in alkaline solutions of sodium hydroxide, NaOH, or potassium hydroxide, KOH, thereby producing NTs/NRs, and NWs, respectively. Such nanostructures self-assemble into fibrous structures that, in turn, form free flowing, mesoporous particles. The production of these materials from common binary Ti precursors under such relatively mild reaction conditions highlights a breakthrough in the efficient and scalable production of low-dimensional titanate materials. We synthesized and characterized these materials under various conditions and believe they present significant potential where similar titanate species have succeeded. [Display omitted] [ABSTRACT FROM AUTHOR]

With the development of electronic information technology, people have put forward more requirements for miniaturization and multifunctionality of electronic devices. Obtaining dielectric materials with good dielectric response is a research challenge. Calcium copper titanate (CCTO) ceramics have attracted widespread attention from researchers due to their high dielectric constant, good stability, and strong applicability. However, it has a significant dielectric loss, which limits its further development and application. Based on this, this paper systematically reviews the research progress of CCTO in terms of dielectric loss, focusing on the influence of different doping modification strategies on the dielectric loss characteristics. The selection of different sites, types, amounts, and properties of dopants has an important impact on dielectric loss, and controlling the grain size and grain boundary resistance can achieve low dielectric loss. The potential future development directions of CCTO mainly include the development of new doping strategies, research on doping modification mechanisms, and applications of materials in multiple fields. This work lays the foundation for the study of CCTO and its application in electronic devices, and is of great significance for the development of new materials and the improvement of their performance. [ABSTRACT FROM AUTHOR]

Sodium bismuth titanate (BNT)-based dielectric capacitors with excellent energy storage performance play an important role in electronics industry. (Sr 1.05 Bi 0.3)ScO 3 (SBS) is introduced into 0.85Bi 0.5 Na 0.5 TiO 3 -0.15NaNbO 3 (BNT-NN) to achieve co-regulation of phase and domain structure. With the introduction of SBS, the dominated pseudocubic phase accompanied by a small percentage of rhombohedral phase are tend to form, and thus induce nanodomain structure with high-density domain walls. Under the excitation of a bias voltage, the induced nanodomains are easier to switch and effectively reduce the residual polarization. Additionally, the homogeneous nanodomains with high-density domain walls will promote large negative built-in voltage which are favorable to rise of breakdown field strength, and thus, optimize the energy storage performance. The co-regulation of phase-domain structure provides an idea for designing ferroelectrics with good energy storage performance. [ABSTRACT FROM AUTHOR]

In this work, we report on the polycrystalline Sr 1-3x/2 Eu x TiO 3 , x = 0.01–0.07 materials prepared by the sol-gel route and their optical properties. The Sr 1-3x/2 Eu x TiO 3 powders calcined at 1000 °C showed a microstructure consisting of nanograins with average particle size decreasing from 86.32 nm to 51.87 nm with the increase of Eu amount from 1 at% to 7 at% Eu, as revealed SEM and TEM investigations. Optimized sintering conditions of Eu-doped SrTiO 3 ceramics (1400 °C, 4h in air) led to materials with a single phase of cubic SrTiO 3. The high purity and uniform distribution of the chemical elements of as-fabricated SrTiO 3 doped with Eu guaranteed good optical properties. The emission of the Eu3+ ion mainly occurs for the transitions from the 5D 0 level to the levels of the 7F j (j = 1, 2) term, more precisely, the 5D 0 → 7F 2 electric dipole transition (∼615 nm) or the 5D 0 → 7F 1 magnetic dipole transition (∼595 nm). The CIE coordinates of all samples calculated from the emission spectra obtained under the 395 nm and 465 nm excitation wavelength are located in the orange-red region. Therefore, this europium-doped SrTiO 3 phosphor is a promising candidate for application as a red-emitting component in solid-state light sources. [ABSTRACT FROM AUTHOR]

(1- x)[0.82Bi 0.5 Na 0.5 TiO 3 -0.18Bi 0.5 K 0.5 TiO 3 ]- x AgNbO 3 ceramics (abbreviated as BNKT-100 x AN , x = 0–0.06) are fabricated by the solid state reaction method. It is discovered that silver niobate is completely dissolved into the lattice of 0.82Bi 0.5 Na 0.5 TiO 3 -0.18Bi 0.5 K 0.5 TiO 3 ceramics based on characterization. The relaxation mechanism and characteristics of BNKT-100 x AN ceramics are analyzed by dielectric temperature spectra and AC impedance spectra. The content of ordered domains and PNRs of BNKT-4AN ceramics is optimum, which enables it possess excellent electrostrain of 0.51%. The electrostrain almost remain constant after the 104 cycles test, suggesting that it also has great fatigue resistance. After polarization at high temperature, large electrostrain of 1.4% and inverse piezoelectric constants of 2004 pm/V are obtained at 150 °C in BNKT-4AN ceramics. The ultrahigh electrostrain is mainly promoted by the larger polarizability of the <111>-oriented and <001>-oriented defect dipoles, the same direction of defect dipoles and the spontaneous polarization direction of phase, the pinning effects of the defect dipoles on the PNRs and the collinear arrangement of the PNRs. This work indicates that lead-free piezoelectric ceramics is hopeful to be applied in piezoelectrics working at high temperature. Simultaneously, a new design paradigm also is provided for the preparation of piezoelectric ceramics with excellent performance. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have emerged as a promising functional filler in nanocomposites due to their unique anisotropy and resilience to harsh conditions. We report herein the use of Ti 0.91 O 2 nanosheets as a protective component against γ -irradiation to cellulose paper. The titanate nanosheets were prepared via a sequence of solid-state synthesis of lepidocrocite-type Cs 0.7 Ti 1.825 O 4 , proton exchange to H 0.7 Ti 1.825 O 4 ·H 2 O, and exfoliation with tetrabutylammonium hydroxide. The nanosheets were incorporated into the commercial cellulose filter paper by a simple dip coating up to 0.6 mg cm−2, equivalent to 10 wt% TiO 2. The nanosheets distribution was demonstrated by energy dispersive X-ray (EDX) mapping, synchrotron radiation X-ray tomographic microscopy (SRXTM), and atomic force microscopy (AFM). It is found that γ -irradiation (up to 50 kGy) destroyed the cellulose I β crystallinity of uncoated paper, but this is less pronounced in the cellulose/titanate nanosheets composite. This was also confirmed by the lack of a 235 nm-absorption characteristics of irradiation-induced decomposition product(s) in nanosheets-containing papers, which also exhibit UVA shielding property. The coated samples remained white while the uncoated ones were darkened with γ -irradiation. In addition, the nanosheets-coated papers showed dielectric permittivity, loss tangent, and AC conductivity which were invariant of the γ -dose, unlike those from the uncoated ones. Our work demonstrates the use of lead-free Ti 0.91 O 2 nanosheets as a γ -shielding component to slow down/prevent structural, optical, and electrical properties damages in cellulose paper, which could extend to other nature-derived materials. [Display omitted] • Simple dip coating of commercial filter paper into titanate nanosheets suspension. • Nanosheets loadings were confirmed by several techniques. • The nanosheets (0.6 mg cm−2, or 10 wt% TiO 2) prevent structural, optical, and electrical properties damages by γ -irradiation (up to 50 kGy). [ABSTRACT FROM AUTHOR]

Sodium titanates represent a promising alternative for the construction of anodes for sodium-ion batteries. To study the electrical response of nanostructured sodium titanate samples under plausible temperature conditions, we evaluate the electrical impedance in the range of temperatures from −30 ∘ C to 50 ∘ C, and the effect of consecutive temperature cycling. Strong changes in electrical properties are observed during the first temperature cycle, followed by a stabilization in the consecutive cycles. This behavior is reversible when the sample is exposed to external conditions and room temperature for less than an hour. Probably a structural and surface water removal and a surface water reabsorption occur, affecting the charge carriers and with it the impedance. Structurally, no differences are detected before and after the cycles, nor when evaluating only the vacuum process. However, when the optical properties are evaluated we find non-reversible changes after the temperature cycles. The optical behavior after the temperature cycling becomes uniform, the same type of electronic defects become predominant and similar direct and indirect band gap values are obtained, regardless of the starting synthesis condition. These results have significant implications for potential technological applications of these materials. [ABSTRACT FROM AUTHOR]

In this study, nanocrystalline niobium-doped lithium titanate Li 4 Ti 5 O 12 (LTO) was successfully synthesized with various stoichiometric ratios (x = 0, 0.025, 0.05, 0.075, 0.1) using a niobium ethoxide precursor via the solid-state synthesis method. X-ray diffraction spectroscopy results revealed that the synthesized samples possess a spinel structure without any impurities, and lattice constants expanded from 8.357 Å to 8.363 Å as the concentration of niobium ions increased. Scanning electron microscopy (SEM) analysis demonstrated that particle sizes ranged from 1.13 to 1.56 μm. The smallest particle size was observed in the LTO-Nb-0.075 sample. The maximum absorptions were detected in the ultraviolet region, and the band gaps of Nb-doped Li 4 Ti 5-x Nb x O 12 (x = 0, 0.025, 0.05, 0.075, 0.1) were determined using Tauc plots. These results showed that the band gaps of Nb-doped LTO were lowered compared to pure LTO, suggesting enhanced electron conductivity. X-ray photoelectron spectroscopy (XPS) measurements confirmed that the band gaps of Nb-doped samples decreased as the formation of oxygen vacancies and Ti3+ ions increased due to Nb5+ substitution. All synthesized samples displayed well-defined redox peaks in pairs during the cyclic voltammetry (CV) measurement. The optimal stoichiometric ratio for doping lithium titanate was found to be x = 0.075, as it yielded the highest specific capacitance of 3.59 F/g and the lowered band gap value of 3.13 eV. Therefore, this study provides further encouragement for applying LTO electrodes in aqueous capacitors and electrical uses. [ABSTRACT FROM AUTHOR]

In this paper, zirconium-doped CaCu 3 Ti 4-x Zr x O 12 (0 ≤ x ≤ 0.3, CCTZO) ceramics were prepared by traditional solid-state reaction. The prepared CaCu 3 Ti 4-x Zr x O 12 display cubic phase structure, as shown by the XRD analysis, and interplanar spacing increase, as obtained by TEM. The surface morphologies, electrical conductivity, optical properties, solar and microwave thermal conversion characteristics of the synthesized samples were investigated in detail. The experimental results indicate that both the solar absorbance and thermal emittance of the samples could be tailored by Zr ions doping. In general, the CaCu 3 Ti 4-x Zr x O 12 system displays relatively high thermal radiation properties, with an optimal composition of CaCu 3 Ti 3.9 Zr 0.1 O 12 exhibiting a solar absorbance of 0.85 and a thermal emittance of 0.75. The incorporated Zr ions enhanced the solar–thermal conversion while weakened the microwave–thermal conversion. Under simulated solar irradiation (3 W/cm2), the equilibrium temperature of CaCu 3 Ti 3.9 Zr 0.1 O 12 could reach above 260 °C. The equilibrium temperature of CaCu 3 Ti 4 O 12 could reach up to 493 °C at a frequency of 2.45 GHz over 140 s. The results demonstrate that the CCTZO ceramics have the potential to emerge as the broadband electromagnetic wave–thermal conversion materials. [ABSTRACT FROM AUTHOR]

An aluminium titanate based (AT) material doped with silica was investigated as refractory model material in order to highlight its thermomechanical properties through various techniques of characterization operating at high temperature such as ultrasonic pulse echography technique operating in long bar mode, acoustic emission, dilatometry and tensile test measurements up to 1400 °C. Young's modulus (MoE) as a function of temperature evolves in the form of a large hysteresis loop with a maximum value of about 170 GPa due to the healing of diffuse microcracks during heating. A sharp decrease in MoE occurs on cooling at about 780 °C, corresponding to the re-opening of the microcracked network due to a high level of stress around AT grains. In addition, during cooling, the dilatometric analysis shows a quasi-linear shrinkage followed by a sudden non-linear expansion from 750 °C. The thermal expansion coefficient value determined between 1100 °C and 750 °C is about 8.8 10−6 °C−1. By recording the evolution of the cumulative number of hits as a function of temperature, the results of the acoustic emission clearly confirm the resurgence of microstructural defects at 780 °C. The incremental tensile loading test performed at 1400 °C shows a greater degree of nonlinearity suggesting a higher flexibility of the studied AT due to both the microcracks network and the low viscosity of intergranular glassy phase. Symmetric alternating loading tests have highlighted that the viscous contribution in the viscoelastic behaviour of such materials is increasing from 850 H °C to 1400 H °C as the viscosity of the silica-riched amorphous phase is decreasing. These results are very useful to understand the more sensitive parameters involved in the high thermal shock resistance of aluminium titanate. [ABSTRACT FROM AUTHOR]

Rapid microwave sintering processes with heating rates of up to 300 °C/min and zero isothermal hold have been implemented using a 5 kW 24 GHz gyrotron system for high-temperature microwave processing of materials. ZnO-based varistor ceramics, BaTiO 3 /SrTiO 3 dielectric ceramics and Gd:CeO 2 ceramics for solid electrolyte applications have been sintered to densities of up to 96% of the theoretical value. Using in situ optical dilatometry, correlation between the development of thermal instability under intense volumetric microwave heating and the early onset of densification has been revealed. The influence of the absorbed microwave power on densification and grain growth has been studied by comparing direct and susceptor-assisted microwave heating processes. The possibility of tailoring the microstructure and functional properties of the obtained materials by choosing optimal regimes of rapid microwave sintering is discussed. [ABSTRACT FROM AUTHOR]

0.96BaTiO 3 -0.04Bi(Mg 1/2 Ti 1/2)O 3 (0.96BT-0.04BMT) + y wt.% Nb 2 O 5 ceramics (0.0 ≤ y ≤ 2.0) were sintered at 1275 °C to fabricate a ceramic with a large ε r for an X8R multilayer ceramic capacitor (MLCC). Addition of Nb 2 O 5 afforded a core–shell structure, and the compositions of the core and shell regions were similar to those of BT and BT-BMT, respectively. The sample (y = 1.25) exhibited a large ε r of 2285 with a good temperature stability satisfying the X8R specification because of a broad shell-region phase-transition peak at −17 °C and a decreased ε r of the core-region phase-transition peak. The 0.1 wt% BaO–CaO–SiO 2 (BCS) was used to reduce the sintering temperature, and the 9-layered MLCC produced using a BCS-doped 0.96BT-0.04BMT + 1.25 wt% Nb 2 O 5 ceramic at 1200 °C showed a large capacitance of 67 nF with a good temperature stability thus complying with EIA-X8R regulations. [ABSTRACT FROM AUTHOR]

Nickel-zinc ferrite (NZF) discs and magnesium calcium titanite (MCT) dielectric ceramic discs were laminated and co-fired to prepare NZF/MCT bi-layer laminated heterostructure samples. The sintering shrinkage of NZF and MCT was matched well via adjusting the sintering temperature. Ion diffusion curves at the co-fired joint interface were derived by electron-probe microanalysis (EPMA) and fitted basing on infinite diffusion coupling model. Ion diffusion mechanism at the co-fired joint interface was investigated in detail. The results show that Zn2+ ions have the highest diffusion coefficient because of the smaller ion radius which is benefit for interstitial diffusion, while Ca2+ ions have the lowest diffusion coefficient and segregate along the interface of MCT side. Fe3+ ions have the biggest diffusion width because of the interstitial diffusion in the incompletely densified MCT. Sintered at 1260 °C, the maximum interdiffusion width is narrow to be about 102 μm. With increasing temperature, ion diffusion coefficient and diffusion distance both go up obviously. • Nickel-zinc ferrite (NZF) discs and magnesium calcium titanate (MCT) dielectric ceramic discs were co-fired to prepare heterostructure samples. • The microscopic morphology and EDS mappings near the interface of NZF/MCT were observed and identified, respectively. • Cations concentration curves were derived by EPMA and fitted. The diffusion width and diffusion coefficient were determined. • The ion diffusion mechanisms at co-fired joint interface were investigated in detail. [ABSTRACT FROM AUTHOR]

Flexible piezoelectric nanogenerators based on polyvinylidene difluoride (PVDF) and lead magnesium niobate-lead titanate Pb(Mg 1/3 Nb 2/3)O 3 –PbTiO 3 (PMN- x PT compositions for x between 30 and 35) particles with various filler ratios from 10 to 30 vol% were fabricated through the electrospinning method. The phase and microstructural characterizations revealed that the homogenous and continuous fiber-shaped composite structure with good interfacial interaction between the PMN-PT particles and the PVDF matrix was achieved. It was found that the diameter of the neat PVDF fibers was approximately 354 nm, whereas the PVDF/PMN-35PT fibers with ceramic particle concentrations of 10, 20, and 30 vol% had average diameters of 317, 249, and 163 nm, respectively. The piezoelectric performance tests indicated that the 30 vol%PVDF/PMN-35PT nanogenerator had a 3 times greater electrical power efficiency (10.59 μW) at 20 Hz compared to that of the pure PVDF nanogenerator (3.56 μW) at 15 Hz under the same resistance load of 1 MΩ. All in all, the incorporation of PMNT-PT particles into the PVDF appears to be a good approach for the fabrication of high-performance flexible piezoelectric nanogenerator applications for biomechanical energy harvesting of devices converting the mechanical movements of organs such as cardiac and lung into electrical energy. [ABSTRACT FROM AUTHOR]

Ceramic composites with negative permittivity have provoked considerable interests of researchers in electronic and dielectric devices due to the extraordinary electromagnetic performance in radio-frequency (RF) region. Herein, graphene/CaCu 3 Ti 4 O 12 (GR/CCTO) ceramic composites were spark plasma sintered, of which the dielectric and thermal properties were demonstrated at RF region. An electrical percolation was identified with GR content varying from 10 wt% to 14 wt% which presenting as a dramatic increase of ac conductivity. The conduction mechanism changed from hopping conductivity to metal-like conductivity. Meanwhile, the real permittivity (ε′) turned from positive to negative which indicating an intrinsic transition of dielectric response mechanism. Therefore, Drude model was applied to elucidate the RF negative permittivity (ε' < 0) which manifesting the low-frequency plasmonic state of delocalized electrons in composites. The constructed GR networks in composites also leaded to the enhanced thermal conductivity due to the dominating contribution of phonon vibration in GR sheets. Besides, theoretical models of capacitive and inductive equivalent circuits were used on impedance spectra which successfully clarified the inductive character of negative permittivity. This work benefits expounding the generation and regulation mechanism of negative permittivity and will be favorable to exploring brand-new applications of ceramic composites. [ABSTRACT FROM AUTHOR]

Porous Ti–Zr–Cu–Pd–Sn bulk metallic glass (BMG) with bone-like mechanical properties, created using the one-step spark plasma sintering (SPS) process, offers a significant deal of potential for usage as orthopedic biomaterials. However, due to a lack of bioactivity and an inability to manage the antibacterial ability, its therapeutic usefulness is severely limited. Here, a bioactive titanate layer was synthesized in situ on the inner and outer surfaces of porous Ti-based BMG by a chemical treatment method. This research not only significantly confers a bone-bonding capability to porous Ti-based BMG, but it also achieves the modulation of Cu2+ ion release rate, substantially lowering the potential biological toxicity of porous Ti-based BMG. In parallel, a thorough analysis of the structure, morphology, mechanical characteristics, corrosion resistance, and antibacterial properties of the porous BMG before and after chemical treatment was conducted. It is anticipated that this discovery will assist to further advance the use of porous Ti-based BMG as orthopedic biomaterials. [Display omitted] [ABSTRACT FROM AUTHOR]

Nickel titanate is a yellow-brown pigment which adopts the ilmenite crystal structure as corundum and hematite. Since Cr doped Al 2 O 3 and Fe 2 O 3 present a thermochromic behavior, NiTiO 3 was also studied for its potential ability to change colour with temperature. Powders were synthesized via a modified Pechini method followed by a calcination step at 700 °C. The thermochromic properties in the 20 °C–400 °C temperature range were collected via the determination of the colorimetric L*a*b* parameters. Namely, the hue continuously shifts from yellow-brown to red-brown, with L*a*b* parameters moving from 60.4/19.2/58.5 to 42.9/30.5/43.1. This colour change is fully reversible even after several cycling. Temperature dependent UV–vis spectroscopy showed that the transparency window at 550–650 nm at room temperature shifts to 575–650 nm at 400 °C. This fully explains the observed colour change. Finally, the effects of Cu or Co doping on NiTiO 3 optical and thermochromic properties were also investigated. [ABSTRACT FROM AUTHOR]

Eu3+ activated zinc titanate red-emitting phosphors have been synthesized by a solid state reaction, and Li+ is added as the charge compensator to tune the optical performances of the phosphors. The structure of samples synthesized at different temperature reveals temperature dependence. The crystallization of particles is improved with increasing calcination temperature. The surface morphology and element distribution of the samples are observed by scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS). Various elements are evenly distributed in the matrix materials. The luminescence intensity of Eu3+ is effectively improved by co-doping Li+, and the luminescence intensity of the phosphor with Li+ content of 5 mol% and 7 mol% is twice than that of the phosphor without Li + when the annealing temperature is 600 °C. While the influence of Li + on the photoluminescence performance becomes weaker with the annealing temperature increasing. The highest relative sensitivity of 0.65%/K is obtained in the sample annealed at 1000 °C, which is not affected by the Li+ dopants. [ABSTRACT FROM AUTHOR]

The exploration of the size and shape of well-defined strontium titanate (SrTiO 3) nanocubes remains challenging despite the increasing interest in this material, owing to its remarkable morphology-dependent electron and phonon transport abilities. This paper discusses the controllable solvothermal synthesis of SrTiO 3 nanocube with tunable morphology in the ethanol-water solvent, using cetyltrimethylammonium bromide (CTAB) as a capping agent and tert-butylamine (TBA) as a mineralizer. The SrTiO 3 nanocubes crystallization can be described as the dissolution-precipitation process, and the addition of CTAB and TBA affects the transformation of oriented attachment in forming a well-defined nanocube. In this study, the X-Ray Diffraction (XRD) data supported by the Le Bail refinement analysis revealed the shape-dependent tuning in lattice parameters of polycrystalline samples. The electrostatic interaction of CTAB and TBA on the particle surface of SrTiO 3 was proven by the appearance of specific absorption peaks in the IR spectrum. XPS spectra show the chemical shift toward higher binding energy confirming the attraction of the nitrogen N-containing groups from CTAB and TBA with SrTiO 3 through the synergistic capping effect. Meanwhile, HRTEM images showed that the nanocube particles have a uniform shape, sharp edges and vertices, flat faces, and narrow size distribution. In addition, the electrical conductivity in the bulk samples with uniform nanocubes increases three-fold compared to non-uniform nanocubes. These findings can potentially set a foundation for establishing synthesis techniques for producing morphologically-distinct particles based on surface interactions through the selective adsorption of additives. [ABSTRACT FROM AUTHOR]

The efficient TiO 2 NTs/Sn 3 O 4 photocatalysts were synthesized by the hydrothermal deposition of Sn 3 O 4 on TiO 2 nanotube arrays (TiO 2 NTs), and the morphology, microstructure and photocatalytic property were adjusted by changing the alkali kind. The TiO 2 NTs/Sn 3 O 4 prepared with NaOH exhibited the outstanding photoelectric conversion and photocatalytic environment remediation/H 2 evolution. The methylene blue (MB) dye and Cr(VI) could be removed by the as-prepared photocatalysts under visible light irradiation, and •O 2 −/•OH radicals were the main active species for MB photodegradation. Furthermore, the high photocatalytic H 2 evolution rate was as high as 6.49 μmol cm−2 h−1. The outstanding photocatalytic activity and stability of TiO 2 NTs/Sn 3 O 4 photocatalysts would exhibit attractive prospect in the wastewater remediation and electric energy/hydrogen generation. [ABSTRACT FROM AUTHOR]

A mixed perovskite titanate-aluminate [(1- x)(Sr 0.6 La 0.2 Ce 0.2 Ti 0.8 Mg 0.2 O 3)- x NdAlO 3 for x = 0.1 to 0.4] solid solution was successfully synthesized. X-ray diffraction patterns (XRD) and Rietveld refinement results indicated a stable perovskite phase with a cubic structure, in which Nd3+ occupies the A-site randomly while Al3+ occupies the B-site. No additional reflection spots (superlattice reflections) were detected in the HRTEM pattern (see SAED), confirming the cubic symmetry. All samples showed small Urbach tails, mainly due to compositional disorder. Microstructural analysis based on atomic force microscopy (AFM) showed no traces of impurity phases. For x = 0.4, excellent microwave dielectric properties (MWD) are obtained with a quality factor (Q × f) of 37,131 GHz at f = 5.2801 GHz, relative permittivity (ε r) of 43, and temperature coefficient of resonant frequency (τ f) of +1.3 ppm/°C. Variations in ε r , Q × f values, and τ f may be related to changes in relative density (ρ rel), ion polarizability, optical band gap, and tolerance factor, respectively. [ABSTRACT FROM AUTHOR]

The paper presents the results of preparing biphase SrTiO 3 –TiO 2 ceramics as a promising system for n -type thermoelectrics using the features of a two-dimensional electron gas. Ceramics was obtained by reactive spark plasma sintering of SrCO 3 and TiO 2. The dynamics of phase transformations are shown; it is clarified that phase transformations are not the driving force of sintering. The mutual stabilization of the SrTiO 3 and TiO 2 phases is shown. Unique data on the assessment of the temperature gradient in the system have been obtained. A comparison of the thermoelectric characteristics of biphasic ceramics and its constituent phases allows concluding that the role of the two-dimensional electron gas is reduced to modulating the properties of bulk phases. Clear signs of size quantization were detected by the X-ray luminescence method, which is expressed in the blueshift of the luminescence spectrum by 22.3 ± 0.8 meV. [ABSTRACT FROM AUTHOR]

In order to realize the recycling of calcium alumino-titanate (CAT, a solid waste), the effect of small amounts (3–9% weight ratio) of CAT on the sintering properties of the mullite–cordierite system was investigated. The thermal-shock stability, volume stability, and mechanical properties of samples with different amounts of CAT were characterized and tested. The influence of CAT on the phase composition and microstructure of the mullite–cordierite system was also deduced from thermodynamic calculations. Experimental results, which agreed with the calculations, demonstrate that CAT could promote the close combination and aggregation of matrix materials, thus strengthening the consolidation process and enhancing desirable properties. [ABSTRACT FROM AUTHOR]

The study of the parameters of energy harvesting and storage in the lead-free solid solution BaTi 0.86 Sn 0.14 O 3 (BTSnO) was performed. The permittivity shows the behavior similar to a diffuse phase transition with the critical exponent γ = 1.84, which is close to the value characteristic of relaxors. Large values of the recoverable energy density, W rec =(5.8–7.0)∙104 J/m3, and the energy storage efficiency coefficient, η=(82–94) %, are implemented in a wide temperature range, 30–87°С, at a low electric field, E = 18.5 kV/cm. For the first time, the analysis of the Olsen cycle was performed using two phase diagrams: polarization – electric field and entropy – temperature. A fairly good agreement was found between the values of the energy conversion density, N D ≈ 0.15 J/cm3, which was determined using two approaches. A universal parameter is proposed for comparing the energy harvesting density for the materials studied in different ranges of temperature and electric fields. [ABSTRACT FROM AUTHOR]

Nb-doped SrTiO 3 single crystal exhibited a giant permittivity (>6.5 × 105) with an acceptably low dielectric loss (<10−1) in a wide temperature range from −120 to 200 °C, making this material a good candidate for energy storage devices and modern microelectronics components. The mechanisms responsible for the giant permittivity of Nb-doped SrTiO 3 single crystals were studied by means of microstructure characterizations, dielectric measurements, and density-functional theory calculations. A chemical compositional gradient extending from the surfaces was found, forming the internal barrier layer capacitance (IBLC) effect. Polar nanoregions (PNRs) were observed because of local fluctuations in distributions of Nb and oxygen vacancies. While both compositional gradients and local chemistry fluctuations increased polarization of the Nb-doped SrTiO 3 single crystals, the local fluctuations dominated enhanced polarizability. This work suggests that optimizing local structures and chemistries in dielectrics is an effective way to tailor the desired dielectric performance. [ABSTRACT FROM AUTHOR]

The flexoelectric effect, a type of electromechanical property, is proposed to generate thermal-electrical like response in ferroelectric ceramics; however, presently, the electric current output achieved is small. Here, we show that changing the composition of the Na 0.5 Bi 0.5 TiO 3 -based ceramics to improve their conductivity can enhance their thermal-electrical like response to several orders of magnitude larger than that reported earlier. We also found that the measured thermal-electrical like response mainly originates from the spontaneously polarised surface existing in ferroelectrics, which generates a flexoelectric-like response under inhomogeneous deformation. The coupling of the flexoelectric-like response and high conductivity leads to a large thermal-electrical like response. [ABSTRACT FROM AUTHOR]

An eco-friendly, cost-effective route for fabrication of silver (Ag) coatings on the surface of magnesium titanate ceramic by electroless plating (EP) based on a novel Ni–P activation process was developed successfully. Coarsened ceramic surface was implanted in situ abundant nano-scale Ni–P spherical active particles via facilely soaking in aqueous solution containing nickel sulphate as Ni source, sodium hypophosphite as major reducing agent and introducing a trace of sodium borohydride to induce initial deposition. The validity of the novel activation process was confirmed by the subsequent experimental fact that Ag EP coatings could deposit smoothly. The surface and cross-section micro-morphologies of typical samples and their element constituent as well as distribution were characterized by SEM and EDS. The deposition rate of Ag coatings and their comprehensive performances including appearance, electric conductivity, adhesion and microhardness were evaluated. The results indicates that the novel Ni–P process could provide the best activating effect to ensure the deposition of high-quality Ag coatings by comparison with traditional Ni–B activation and classical stannous activation. [Display omitted] [ABSTRACT FROM AUTHOR]

Herein, titanate-based perovskite CaTiO 3 nanosheets were successfully designed via boron nitride quantum dots (BNQDs) to fabricate CaTiO 3 /BNQDs catalyst. The as-fabricated composite catalysts were analysed by transmission electron microscope (TEM), scanning electron microscopy coupled with energy dispersive spectrometry (SEM-EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), X-ray diffraction (XRD), UV–vis spectroscopy (UV-DRS), photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) techniques. SEM-Mapping analysis showed that the boron and nitrogen elements dispersed well over the CaTiO 3 surface which was useful for building electronic channels for rapid transport of photo-induced charge pairs. TEM images verified the attachment of BNQDs around the surface of host CaTiO 3 forming intimate interface while the distribution of chemical states was observed by XPS analysis demonstrating strong coupling effect between BNQDs and CaTiO 3 through Ti–O–N and Ti–O–B bonds. Moreover, PL and light absorption properties enhanced with the quantum confinement effect of BNQDs. As expected, the photocatalytic degradation rate of CaTiO 3 /BNQDs was increased to k app = 0.015 min− 1 with optimum BNQDs loading, which was 2.31 times folder than that of bare CaTiO 3 (0.006 min− 1). The enhanced photocatalytic efficiency was observed for CaTiO 3 /BNQDs than pristine perovskite on account of formation of electron tapping sites, decreased band gap energy and hindered recombination rate. On the other hand, in the presence of H 2 O 2 , the degradation percentage increased from 88.5% to 92.1% at the end of 120 min of irradiation while 96.8% of TC was quickly degraded within 60 min after activating with peroxymonosulfate which created strong sulphate radicals. Radical trapping tests indicated that the photo-generated holes were the primary active species in the photocatalytic mechanism. Moreover, CaTiO 3 /BNQDs catalyst showed excellent stability in recycling tests. Besides, the possible degradation mechanism was proposed. This study shed light on the significance of BNQDs in the enhancement of the photocatalytic activities of titanate-based perovskite for effective degradation of tetracycline antibiotic in contaminated water. [Display omitted] [ABSTRACT FROM AUTHOR]

Synthesis of materials in Ni/SrTiO 3 system was undertaken. Perovskite structure material with nominal composition SrTi 0.98 O 3 was synthesised by the sol-gel method. Nickel was introduced into the system by the wet impregnation method followed by proper thermal treatment. Two research paths were carried out: the evaluation of sintering conditions on material properties (sintering temperature: 1100, 1200, 1300 and 1400 °C; sintering time: 1, 3 and 5 h for sintering at 1300 °C) and the effect of nickel addition on the material properties - 1, 2, and 5 mol% of Ni compared to the amount of Ti was introduced into the analysed system. The microstructures of the materials, together with their structural (XRD analysis) and electrical (total conductivity and Seebeck coefficient) properties, were determined. Furthermore, temperature-programmed reduction (TPR) and temperature-programmed oxidation (TPOx) measurements were performed to evaluate the materials' redox properties. It was shown that less than 1 mol% of Ni could be incorporated into the strontium titanate structure when a wet impregnation was chosen as the method for the introduction of Ni into the SrTiO 3 -based system. NiO and, for the highest amount of introduced nickel, also NiTiO 3 were the main additional nickel-containing phases. For all materials synthesised in the Ni/SrTiO 3 system, the positive value of the Seebeck coefficient was observed, suggesting that nickel is an acceptor-type dopant while incorporated into the perovskite structure. However, the TPR measurements clearly imply that nickel can be incorporated into the strontium titanate structure in various oxidation states. [ABSTRACT FROM AUTHOR]

Anomalous dielectric relaxation appears in Nb-doped SrTiO 3 (SNT) single crystal with relaxation rate displaying unusual slowing down with increasing temperature. Dielectric measurements show that the resistivity increases with temperature. Raman spectrum and the spherical aberration-corrected transmission electron microscope (STEM) show the existence of polar nano regions (PNRs) in the crystal. The temperature-dependence of DC conductivity and current-voltage (I–V) curves suggest that this anomalous behavior happens at the interfaces of PNRs. The evolution of the anomalous relaxation peak in the annealed samples indicates that this effect is simultaneously affected by the carrier concentration and the interface structure. The anomalous dielectric relaxation is reminiscent of the positive temperature coefficient of resistance (PTCR) effect in a polycrystalline material. The resistive switching effect makes such materials to have potential application value in switches, sensors, and device miniaturization. [ABSTRACT FROM AUTHOR]

TiO 2 -added Ba 4 (Sm 0.65 Nd 0.35) 9.33 Ti 17.75 Al 0.33 O 54 (BSNTA) ceramics were fabricated with a solid-state reaction method. Slight TiO 2 addition increased the dielectric constant (ε r) of BSNTA ceramics and brought about a near-zero temperature coefficient of resonant frequency (τ f). Sintering in oxygen increased the density of TiO 2 -added BSNTA ceramics and surprisingly concurrently improved the ε r and Q × f value. Thermally stimulated depolarization current (TSDC) measurements indicated that TiO 2 addition introduced oxygen vacancies (V O..) and Ti Ti ' − V O.. defect dipoles and that an oxygen-sufficient sintering atmosphere decreased the concentration of these defects and thus increased Q × f values. From the viewpoint of defect behaviors, this observation offered original insight into the mechanism by which the sintering atmosphere had impacts on the Q × f value of titanate ceramics. Satisfying dielectric properties (ε r = 79.5, Q × f = 14,840 GHz, τ f = 0 ppm/°C) were attained in oxygen-sintered BSNTA-0.6%TiO 2 ceramics that might be suitable for the manufacture of miniature microwave devices such as filters and antennas. [ABSTRACT FROM AUTHOR]

K+/Na+ ion electrochemical capacitors have been studied for energy storage because of their abundant resources and higher theoretical energy density. However, the origin of the storage mechanism and low structural stability still remain elusive due to the large radius of Na+ and K+. Thus, the novel of NaTiO 2 /Ti 3 C 2 and KTiO 2 /Ti 3 C 2 electrodes are prepared by a simple hydrothermal self-growth. As a comparison, the reversible capacity of the two electrodes reach 307.43 F g−1 and 261.3 F g−1 at 0.5 A g−1, respectively. Further tests show that their capacitance retention achieve 82.4% and 85.7% after 3000 cycles at 2.0 A g−1, respectively. The good energy storage performance is based on the interlayer structure of Ti 3 C 2 MXene retained by the prepared NaTiO 2 /Ti 3 C 2 and KTiO 2 /Ti 3 C 2 anode. Furthermore, the excellent electrochemical performance is mainly attributable to the TiO 2 nanoribbons generated in-situ not only extended the interlayer spacing, but accelerated the cation transmission between the communication layers. By building a conductive network between the layers, Na+/K+ and F− form a strong covalent bonds between the MXene layers, which provides additional pseudocapacitance properties. This work provides a new way for the preparation of high-performance Na+/K+ electrochemical capacitors. [ABSTRACT FROM AUTHOR]

The effect of Nb/Ta donor doping on the piezoelectricity, thermal stability, and fatigue resistance of bismuth titanate Bi 4 Ti 3 O 12 (BIT) ceramics was investigated in relation to their structural and oxygen vacancy-related electrical properties. As the Nb/Ta doping amount increased, the activation energy of oxygen vacancy conduction increased, indicating a reduction in the concentration of oxygen vacancies. The improved electrical insulating properties of the Nb/Ta-doped Bi 4 Ti 3 O 12 ceramics (BTNT) with fewer oxygen vacancies, contributed to their effective poling and strong piezoelectricity. Outstanding piezoelectric performance with high piezoelectric constant (39 pC/N) and Curie temperature (690 °C) could be achieved in the 0.005 mol Nb/Ta-doped BTNT ceramic with high density and anisotropic grain growth. The BTNT ceramics exhibited superior thermal aging stability and fatigue resistance compared to the BIT ceramic, suggesting that the reduction of oxygen vacancy defects plays a decisive role in enhancing elevated-temperature-induced and electric-field-induced degradation stabilities. [ABSTRACT FROM AUTHOR]

In this work, a significant enhancement of pyrocatalysis is found in barium calcium titanate @carbon (Ba 0.8 Ca 0.2 TiO 3 @C) hybrid nanofibers hydrothermally synthesized and designed to decompose rhodamine B (RhB) dye. The pure Ba 0.8 Ca 0.2 TiO 3 can decompose the RhB dye at 30–60 °C cold-hot cycles with a final decomposition ratio of 31.3%. As the content of C mixed in Ba 0.8 Ca 0.2 TiO 3 gradually increases from 0 to 5 wt%, the decomposition ratio of RhB first increases and then decreases, with the highest decomposition ratio of 76.6%, when the content of C is 3 wt%. The enhancement of pyrocatalytic activity could be attributed to the fact that the presence of C accelerates the carrier mobility and impedes the free charges recombination in the pyrocatalysis process. With the enhanced pyrocatalytic performance, Ba 0.8 Ca 0.2 TiO 3 @C hybrid nanofibers have tremendous potential for the alleviation of dye wastewater pollution through utilizing alternative cold-hot energy variation. [ABSTRACT FROM AUTHOR]