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Rare-earth titanate oxides are believed to be prospective functional materials for photocatalytic and photoluminescent applications because of their excellent optical properties and thermal stability of their physical properties. However, the relationships between optical properties and photoelectron trapping mechanisms are unclear. Herein, the structure, electronic, and optical properties of pyrochlore-structure Re2Ti2O7 (Re = Sm and Eu) were investigated using the first-principles approach with the Hubbard parameter U (GGA + U). The calculated bandgap is 2.5 eV for Sm2Ti2O7 and 2.4 eV for Eu2Ti2O7, which is in good agreement with the experimental observation. The results indicate that the strongly localized f states at the top of valence band are charge-trapping sites for photoexcitation of Re2Ti2O7, where electrons can absorb photon energy and transfer from the valence band to the conduction band, resulting in the photocatalytic and/or fluorescent effects in the visible and early UV regions. The important optical parameters, dielectric function ε (ω) , refractive index n (ω) , extinction coefficient k (ω) , reflectivity R (ω) , absorption coefficient I (ω) , optical conductivity σ (ω) , and electron energy-loss L (ω) were studied in detail, indicating that these optical parameters of Sm2Ti2O7 and Eu2Ti2O7 are insensitive to the ultra-violet (UV) radiation, but both Sm2Ti2O7 and Eu2Ti2O7 exhibit excellent optical properties in the visible and early UV regions. This work provides a clear understanding on the photoelectron trapping mechanism of pyrochlore-structure Re2Ti2O7, which will help to improve the photocatalytic and photoluminescent performance of Re2Ti2O7 and broaden their applications. [ABSTRACT FROM AUTHOR]

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]

Demand on high‐performance ion exchangers is ever‐increasing in energy and environment applications. Among many cation exchangers, layered alkali titanates generally show larger cation exchange capacity, but slower cation exchange rate due to their 2D micrometer‐size particle morphologies, which limits their practical applications. Here, a rational conversion of a layered sodium titanate, Na2Ti3O7, is reported to the corresponding 1D ultra‐narrow nanowires via hydrothermal treatment under basic conditions. The formation of nanowires is thought to involve the partial exfoliation of Na2Ti3O7 to form thin plate‐like particles that subsequently split into nanowires along a crystallographically defined, chemically selective weakness in the Na2Ti3O7 crystals. This process is similar to a recently burgeoning materials design using atomic‐level weakness in solids, such as zeolites and metal‐organic frameworks. The proposed formation scheme is further supported by comparative experiments performed on another layered alkali titanate, K0.8Ti1.73Li0.27O4, which possesses randomly distributed defects at the Ti sites. Thanks to the shortening of diffusion path lengths of the interlayer cations, the resulting Na2Ti3O7 nanowires show an excellent cation exchange performance toward Cd2+ in aqueous solution, exceeding several existing cation exchangers such as zeolites and organic resins. [ABSTRACT FROM AUTHOR]

Exploring semiconductor materials with enhanced photocatalytic activity is essential for practical applications. This review provides a comprehensive overview of the photocatalytic reaction mechanisms. The discussion highlights recent progress in perovskite oxide materials for various environmental and energy applications, including H2/O2 production, organic pollutant degradation, heavy metal removal, radionuclide removal, CO2 reduction, and N2 fixation. The structural characteristics of perovskite oxides including titanates, tantalates, niobates, ferrites, and complex perovskite oxides are discussed, focusing on current strategies to enhance their photocatalytic activity. Furthermore, recent advances in the design and development of perovskite-based photocatalytic reactors are reviewed, emphasizing their potential for increased efficiency and practical implementation. This review aims to provide insights into the abilities, research gaps, future perspectives, and recommendations for further studies of perovskite oxide photocatalysts in addressing significant environmental and energy challenges. [ABSTRACT FROM AUTHOR]

Adding excessive metal oxide doping to a powder batch is a known way to compensate for the loss of volatile cation species during high temperature sintering. An important case in the piezoelectric ceramics is the bismuth oxide in the lead-free ferroelectric ceramic bismuth sodium titanate (BNT). Building from the earlier knowledge about excessive bismuth oxide's influences on the properties of BNT, we further note that varying the sintering temperature can both control the distribution of excessive Bi3+ and impact the relaxor/normal ferroelectric behaviors and corresponding phase transition. In addition to the nature of polarization, the sintering temperature also significantly manipulates the electrical conductivity. A hypothetical mechanism for the resistive grain boundary is proposed, based on inferences from electrical—microstructure—processing relations in 85% Bi0.5Na0.5TiO3-15% BaTiO3 with batched Bi2O3 excess and acceptor Mg2+ in a co-doped strategy. [ABSTRACT FROM AUTHOR]

Whispering gallery mode resonators (WGMRs) have garnered significant interest due to their potential applications in the fields of electro-optic modulation and microwave to optical photon conversion. In this study, we have leveraged an electro-optic crystal, lead indium niobate-lead magnesium niobate-lead titanate (PIN-PMN-PT), to fabricate a high-quality WGMR. Our investigation revealed that the crystal composition used in this work is 0.24PIN-0.45PMN-0.31PT, and each element of the whole sample is homogeneously distributed. The dielectric properties of the sample revealed the necessity of limiting the temperature and external electric field frequency to below 100 °C and 106 Hz, respectively. The obtained optical quality factor value (Q value) of the resonator is ∼0.7 × 105. Impressively, our resonator could be conveniently tuned by exploiting the enormous inverse piezoelectric effect d31 of the crystal, thereby alleviating the need for precise fabrication. Furthermore, a theoretical analysis of our resonator revealed that a calculated resonance wavelength shift is within a broad range of 2.16 nm. Intriguingly, if the surface roughness of the resonator is reduced tenfold, we can increase the calculated Q value dependent on surface scattering by 104. Our finding showcases the tremendous potential of the PIN-PMN-PT crystal-based WGMR as versatile building blocks for a variety of applications in the burgeoning field of photonic technology. [ABSTRACT FROM AUTHOR]

Solid solutions of rare earth titanates with high contents of rare earth oxides of up to 50-62% have been synthesized by the co-precipitation method and their structure, microstructure and conductivity in dry and wet air have been studied. Proton conductors have been found for the first time in solid solutions of rare earth titanates with a high content of Ln2O3 (>50%) with a nominal formula composition of (LnxTi1-x)4O8-2x (Ln = Yb, Er, Ho, 0.667 = x = 0.765). Among (LnxTi1-x)4O8-2x (Ln = Yb, Er, Ho, x = 0.684), (HoxTi1-x)4O8-2x (x = 0.684) showed the maximum conductivity in wet air. In this context, four additional compositions (HoxTi1-x)4O8-2x (x = 0.718, 0.734, 0.75, and 0.765) were synthesized in the holmium series. An increase in the holmium content leads to an increase in the proton transfer coefficients; at the same time, a more complex nature of the dependence of the conductivity under dry and wet atmospheres is observed. For the fluorite-like solid solution (HoxTi1-x)4O8-2x (0.701 = x = 0.765), the proton transfer coefficients were found to be ~0.9 in the range of 200-450 °C. As the temperature continues to rise, the proton conductivity decreases quite sharply and the transfer coefficient becomes as low as 0.3 at 700 °C. The increase in proton conductivity in the Yb-Er-Ho series is associated with an increase in the hydrophilic properties of rare earth cations. In the (HoxTi1-x)4O8-2x (x = 0.667 = x = 0.765) series, the conductivity in wet air was ~1 × 10-6 S cm-1 at 450 °C for most compositions. The conductivity of ceramics with x = 0.701 and 0.75 is about 2 times higher, which may be due to the optimal size of pyrochlore nanodomains in the fluorite matrix for x = 0.701 and the formation of pure fluorite for x = 0.75, respectively. [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]

Rare-earth titanate pyrochlores have attracted significant attention for their unique magnetic frustration; however, research on the origin of low-temperature dielectric dispersion and the relationship between dielectric properties and structure lags far behind. Here, by systematically investigating the dielectric properties of representative rare-earth titanates R2Ti2O7 (R = La, Nd, Sm, Er, Yb, and Lu), we demonstrate that R2Ti2O7 with a cubic pyrochlore structure exhibits low-temperature dielectric dispersion behavior, while the other compounds with a monoclinic perovskite-like layered structure possess no dispersion behavior but excellent temperature-stable dielectric property. The dielectric dispersion in cubic pyrochlores arises from the structural distortion. Furthermore, the existence of structural distortion is affirmed by the anomalous phonon softening of A1g Raman mode around the dielectric dispersion temperature, and the origin of the structural distortion is attributed to anharmonic phonon–phonon interactions induced by intrinsic vacant oxygen at Wyckoff 8a sites. In addition, with increasing ionic radius from R = Lu to Sm, the increased lattice parameter leads to varied bond length and bond angle of Ti-O(1)-Ti, which strengthens the local lattice distortion of TiO(1)6 octahedra and thus enhances diffusion degree of dielectric dispersion. On the other hand, the absence of intrinsic vacant oxygen site hardly gives rise to the local structural distortion and thus no dielectric dispersion in monoclinic R2Ti2O7. Our work not only clarifies the mechanism of dielectric dispersion but also gives a comprehensive perspective on the structure–property relationship of rare-earth titanates R2Ti2O7, and thus lays a solid foundation for further work on related materials. [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 temperature dependence of the heat capacity of Y2Ti2O7 and Eu2Ti2O7 with a pyrochlore structure in the temperature range of 7–1800 K has been studied. The existence of a small shallow anomaly of the heat capacity of europium titanate in the range of 10–60 K was confirmed. The thermodynamic properties (entropy, enthalpy change, and reduced Gibbs energy) were calculated. Based on the results of calculation of the Gibbs energy of formation of the titanates from oxides it was concluded that both titanates are thermodynamically stable in the high temperature region. [ABSTRACT FROM AUTHOR]

A hierarchical sea urchin-like hybrid metal oxide nanostructure of ZnO nanorods deposited on TiO2 porous hollow hemispheres with a thin zinc titanate interface layer is specifically designed and synthesized to form a combined type I straddling and type II staggered junctions. The HHSs, synthesized by electrospinning, facilitate light trapping and scattering. The ZnO nanorods offer a large surface area for improved surface oxidation kinetics. The interface layer of zinc titanate (ZnTiO3) between the TiO2 HHSs and ZnO nanorods regulates the charge separation in a closely coupled hierarchy structure of ZnO/ZnTiO3/TiO2. The synergistic effects of the improved light trapping, charge separation, and fast surface reaction kinetics result in a superior photoconversion efficiency of 1.07% for the photoelectrochemical water splitting with an outstanding photocurrent density of 2.8 mA cm−2 at 1.23 V versus RHE. [ABSTRACT FROM AUTHOR]

Sodium bismuth titanate‐based materials are expected to be an alternative candidate to lead‐based ceramic materials due to their excellent electrical properties. However, the low depolarization temperature (Td) limits their practical application. In this work, the phase structure evolution and microstructure of 0.9(0.4Na1/2Bi1/2TiO3–0.6BiFeO3)–0.1BaTiO3: xZnO (x = 0.01, 0.03, 0.05, and 0.07) (abbreviated as 100xZnO) composite ceramics are investigated, and their piezoelectric properties are improved by combination of constructing 0–3 type composites and quenching treatment technology. The addition of ZnO can increase both Td and d33 because ZnO can enhance the lattice distortion of rhombohedral phase and lead to the increase in ferroelectric order. Specifically, the optimum composition x = 0.03 obtains the d33 value of 106 pC/N (25°C), which retains 84% of the value at room temperature up to 240°C. And the quenching technology further enhances the ferroelectric order and increases Td, which is up to 280°C for x = 0.03. [ABSTRACT FROM AUTHOR]

Advancing the development of high‐temperature piezoelectric sensors requires high‐performance piezoelectric materials with high Curie temperatures, wherein the charge signals can be efficiently collected at elevated temperatures. The bismuth layer‐structured ferroelectric (BLSF) bismuth titanate‐ferrite (Bi5Ti3FeO15, BTF) has recently attracted considerable attention because of its high Curie temperature (TC) of ∼761°C. However, the piezoelectric properties of BTF‐based compounds have not been extensively investigated because of their extremely poor piezoelectric performances and low electrical resistivities at elevated temperatures. Herein, tungsten‐substituted BTF (BTF‐100xW) ceramics were synthesized using a solid‐state reaction method. X‐ray diffraction refinement results confirmed the lattice distortion of the BO6 octahedron, while piezoelectric force microscopy images verified an increase in the domain wall density with tungsten modification, both of which contribute to significant enhancement of the piezoelectric properties of BTF‐100xW as intrinsic and extrinsic contributions, respectively. Remarkably, BTF‐3W exhibits a high TC of 793°C and a large piezoelectric constant (d33) of 24.3 pC/N, which is over three times that of BTF (7.1 pC/N). Importantly, the substitution of tungsten decreases the concentration of oxygen vacancies, increases the direct current electrical resistivity, and improves the electrical homogeneity at high temperatures, resulting in extremely stable piezoelectric and electromechanical properties at high temperatures, with a high in‐situ relative d33 of >90% at 400°C and a small variation in the electromechanical coupling factor (kp) of <8% at temperatures up to 450°C. These results suggest that the tungsten‐substituted BTF is a potential candidate for high‐temperature piezoelectric ceramics, and is a promising material for applications in high‐temperature piezoelectric sensors. [ABSTRACT FROM AUTHOR]

Sub-micrometer-sized (0.33 μm) polycrystalline powders of calcium copper titanate (CCTO) were synthesized via the solgel method. Compacted calcined powders were sintered at 900 °C/2h to obtain porous (<80% density) pellets. Subsequently, ZnO or SnO2 pastes (∼10 μm grain size) were smeared on either side of the pellets and sintered at 1100 °C/15 h, which yielded dense (>95% density) ceramics. X-ray structural investigations revealed the presence of ZnO or SnO2 traces in the bulk of the CCTO ceramics. Scanning electron microscopy and energy dispersive spectroscopic studies confirmed the diffusion and the segregation of these oxides at the grain boundaries. The dielectric and varistor properties of the ZnO or SnO2 diffused samples were found to be superior to that of pristine CCTO ceramics. For instance, the dielectric constant (ɛ′) of ZnO diffused ceramics exhibited a value as high as 2.4 × 104 (1 kHz, at room temperature) and a dielectric loss (D) of 0.059. Similarly, SnO2 diffused ceramics exhibited a dielectric constant of 2.7 × 104 (1 kHz, at room temperature) associated with a dielectric loss of 0.047. The figure of merit of varistor performance, i.e., nonlinear coefficient (α = 10.6), of the SnO2 diffused sample is significantly higher than that of ZnO diffused (α = 7.4) and pristine CCTO (α = 4.5) ceramics. The dielectric data obtained for both the pristine and ZnO or SnO2 diffused ceramics were rationalized by invoking Cole–Cole analysis. The thermal activation energy was estimated from the temperature-dependent dielectric data besides current (I)–voltage (V) characteristics. Equivalent circuit modeling of the Nyquist plots demonstrated that the inclusion of ZnO and SnO2 layers in CCTO ceramics remarkably improved the grain boundary resistance (Rgb) by 5-fold and 20-fold, respectively, which resulted in making CCTO a better dielectric. This methodology of fabricating ceramics via interfacial engineering could pave the way for obtaining superior CCTO ceramics associated with exotic functional properties. [ABSTRACT FROM AUTHOR]

Structurally correlated ferroelectric phase transitions induced by temperature are reported for the solid solution Pb0.6Ca0.4TiO3 compound. Such phase transitions were analyzed by considering different parameters, such as lattice parameters, microstrain, dielectric properties, and thermal analysis. Synchrotron x-ray diffraction and Rietveld refinement studies revealed a tetragonal symmetry from room temperature up to ∼550 K and uniaxial microstrain from room temperature to ∼400 K. The first thermally driven phase transition observed was from displacive ferroelectric tetragonal symmetry to another non-displacive tetragonal symmetry. The next phase transition was from the tetragonal to cubic. The electric permittivity as a function of temperature for frequency from 1 kHz to 1 MHz and the differential scanning calorimetry report features typical of ferroelectric–paraelectric phase transition only around 400 K, and no other abrupt change in properties is observed at 550 K, indicating the sequence of first- and then second-order phase transition. [ABSTRACT FROM AUTHOR]

Single crystals of undoped and Nb doped sodium and potassium-bismuth titanate at the morphotropic phase boundary (MPB) composition [(Na0.41K0.09Bi0.50)TiO3: NKBT] were grown from high temperature solutions. The effect of Nb doping on the electronic property of NKBT was investigated by optical transmission and photoelectron spectroscopy (PES). The optical absorption shows that the bandgap having the lowest energy is indirect in nature and increases with the increase in the Nb concentration in the lattice. The estimated Urbach energy increases with the increase of Nb concentration signifying an increase in the disorder in the lattice on Nb doping. The PES revealed that the valence band maxima (VBM) exhibit red shift on Nb doping. It also revealed the presence of in-gap states probably due to Ti3+ defect and oxygen vacancy. Moreover, inline with the optical measurement, the PES showed that there is a decrease in the energy gap between the VBM and defect state with the Nb doping. Furthermore, the angle resolved PES measurement confirmed the presence of both the direct and indirect bandgaps in the crystal. [ABSTRACT FROM AUTHOR]

Uniformly acceptor doped Pb(Zr0.48Ti0.52)O3 (PZT) films with 2 mol. % Mg or Fe prepared by chemical solution deposition exhibited decreased dielectric constants and remanent polarizations relative to undoped PZT. For highly accelerated lifetime testing (HALT) at 200 °C and an electric field of 300 kV/cm in the field up direction, the HALT lifetimes (t50) for undoped, Mg-doped, and Fe-doped PZT films were shortened from 2.81 ± 0.1 to 0.21 ± 0.1 and 0.54 ± 0.04 h, respectively. Through thermally stimulated depolarization current measurement, significant V O ∙ ∙ electromigration was found in homogeneously Mg-doped PZT thin films, a major factor in their short HALT lifetime. Because the concentration of oxygen vacancies increases with uniform acceptor doping, the lifetime decreases. In contrast, when a thin layer of Mg-doped or Fe-doped PZT was deposited on undoped PZT or Nb-doped PZT (PNZT), the HALT lifetimes were longer than those of pure PZT or PNZT films. This confirms prior work on PNZT films with a Mn-doped top layer, demonstrating that the HALT lifetime increases for composite films when a layer with multivalent acceptors is present near the negative electrode during HALT. In that case, the compensating electrons are trapped, presumably on the multivalent acceptors, thus increasing the lifetime. [ABSTRACT FROM AUTHOR]

Although a large electric-induced strain has been obtained in sodium bismuth titanate (Bi0.5Na0.5TiO3, BNT)-based ceramics using chemical modifications, the effect of initial BNT-based ceramic's polarity on modulating strain properties was rarely reported. Herein, we comparatively studied the effect of tantalum (Ta) doping on two BNT-based ceramics with different ferroelectric polarities, namely, (Bi0.5Na0.5)0.935Ba0.065TiO3–0.7%Bi2FeCrO6 and (Bi0.98Gd0.02)0.5Na0.5TiO3. The former locates at the morphotropic phase boundary (MPB), whereas the latter is close to pristine BNT ceramics. An effective critical point, located at the crossover between ferroelectric and relaxor, is constructed in the former ceramic and significantly enhances strain properties, whereas a useless one is found in the latter ceramic due to the retention of a non-ergodic relaxor and has merely limited ability to promote strain properties. Our results demonstrate that the ferroelectric polarity of the initial BNT-based ceramic matrix also plays an important role in pursuing high strain properties. [ABSTRACT FROM AUTHOR]

The micrometer-sized nickelate–titanate heterojunctions with LaNiO3 (LNO) electrode have been fabricated to investigate the dominant current transport mechanisms under positive and negative bias. The LNO/SmNiO3 (SNO)/Nb:SrTiO3 (NSTO) heterojunction exhibits a highly rectifying feature with a very low leakage in a broad temperature region (from 200 to 425 K), which is attributed to the formation of a Schottky-like barrier at the SNO/NSTO interface. In addition, it is found that the trap defects (i.e., oxygen vacancies) play an essential role in determining the current density (J)–voltage (V) characteristics irrespective of the voltage polarity. The leakage current at low electric fields (<0.25 MV/cm) is dominated by temperature-enhanced trap assisted tunneling process, which is caused by the interface oxygen vacancy induced states. Further analysis suggests that, at high fields (>1.2 MV/cm), the leakage is ascribed to the bulk-limited field enhanced thermal ionization of trapped carriers in the SNO film (i.e., Poole–Frenkel emission). Specially, the oxygen vacancy redistribution near the SNO/NSTO heterointerface driven by a high temperature (425 K) or high electrical field (>3.8 MV/cm) stress is emphasized to account for the transition from the Schottky contact limited to bulk-limited conduction mechanism (i.e., space charge limited conduction). This work will benefit the further analysis of the resistive switching phenomena in nickelate-based devices, showing a potential for nonvolatile memory applications. [ABSTRACT FROM AUTHOR]

Rare earth and barium titanates are useful as ferroelectric, dielectric, and optical materials. Measurements of their thermophysical properties in the liquid state can help guide melt processing technologies for their manufacture and advance understanding of fragile liquids' behavior and glass formation. Here, we report the density, thermal expansion, viscosity, and surface tension of molten BaTi2O5, BaTi4O9, and 83TiO2-17RE2O3 (RE = La or Nd). Measurements were made using electrostatic levitation and droplet oscillation techniques in microgravity, which provide access to quiescent liquid droplets and deep supercooling of 510–815 K below the equilibrium melting points. Densities were measured over 900–2400 K. Viscosities were similar for all four compositions, increasing from ∼10 mPa s near 2100 K to ∼30 mPa s near 1750 K. Surface tensions were 450–490 dyn cm−1 for the rare earth titanates and 383–395 dyn cm−1 for the barium titanates; surface tensions of all compositions had small or negligible temperature dependence over 1700–2200 K. For solids recovered after melt quenching, x-ray microtomography revealed the fracture mechanics in crystalline products and minimal internal porosity in glass products, likely arising from entrapped gas bubbles. Internal microstructures were generally similar for products processed either in microgravity or in a terrestrial aerodynamic levitator. [ABSTRACT FROM AUTHOR]

In this work, pristine calcium titanate (CaTiO3), polyaniline (PANI), binary PANI@carbon black (CB), and ternary PANI@CB/CaTiO3 composites were synthesized using solid-state and in situ oxidative polymerization method. XRD, FTIR, UV–Vis, PL, FE-SEM, and EDX analyses were studied in order to examine the structural, optical, and morphological properties of all grown samples. XRD, FTIR, FESEM, and EDX findings confirmed the formation of successful chemical organization among PANI, CaTiO3, and CB. The UV–Vis and PL investigation reaffirmed the reduction in optical band gap (2.67 eV–2.56 eV) and charge carrier recombination process due to inclusion of CaTiO3 into CB-reinforced polymer matrix. In photocatalytic experiment, PANI@CB/10%CaTiO3 catalyst showed efficacious performance to degrade the synthetic dyes (99.7% MO and 97.8% MB) after 120-min sunlight irradiation with higher rate and superb stability up-to 5th cycle against MO dye. In kinetic examination, pseudo-first-order kinetic model was obeyed by both dyes. Herein, the bulk heterojunction (BHJ) photovoltaic cell was fabricated by spin-coating the grown samples on FTO glass substrate and thermally evaporating the Al electrode subsequently. The BHJ fabricated by PANI@CB/10%CaTiO3 showed better efficiency (0.541%), photocurrent density (Jsc) (4.21 mA/cm2), and open-circuit voltage (Voc) (0.39 V). [ABSTRACT FROM AUTHOR]

A new hybrid material was created by blending sodium titanate ceramics (Na2Ti3O7/Na2Ti6O13) with a polyvinyl alcohol (PVA) matrix, resulting in enhanced semiconductive characteristics. The synthesis process involved intense ultrasonic treatment and subsequent heat treatment at 900 °C. Utilizing a solvent casting method, Na2Ti3O7/Na2Ti6O13/PVA composites were fabricated. Raman spectra confirmed the presence of PVA chains and distinctive bands of sodium titanates. Elemental analysis verified the existence of Na and Ti in both composites. Morphological observations revealed the formation of irregular agglomerates upon introducing sodium titanates into the PVA structure, leading to a rise in the average surface roughness (Ra) from ~ 1.5 to 7.9 nm post-incorporation of heated Na2Ti3O7/Na2Ti6O13. Differences in morphology between samples loaded with unheated and heated Na2Ti3O7/Na2Ti6O13 suggested a more effective particle incorporation into the polymeric matrix after heat treatment. Electrical measurements indicated that the composite loaded with unheated Na2Ti3O7/Na2Ti6O13 exhibited the lowest electrical resistance (105 Ω) and a relaxation time of 3.16 × 10− 5 s. These results demonstrate that the inclusion of sodium titanate ceramics enhances the semiconductive properties of the PVA matrix. This finding highlights the potential of this material for various electronic applications, including components for solid-state batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] The conversion-type anode material of iron phosphide (FeP) promises enormous prospects for Na-ion battery technology due to its high theoretical capacity and cost-effectiveness. However, the poor reaction kinetics and large volume expansion of FeP significantly degrade the sodium storage, which remains a daunting challenge. Herein, we demonstrate a binder-free nanotube array architecture constructed by FeP@C hybrid on carbon cloth as advanced anodes to achieve fast and stable sodium storage. The nanotubular structure functions in multiple roles of providing short electron/ion transport distances, smooth electrolyte diffusion channels, and abundant active sites. The carbon layer could not only pave high-speed pathways for electron conductance but also cushion the volume change of FeP. Benefiting from these structural virtues, the FeP@C anode receives a high reversible capacity of 881.7 mAh/g at 0.1 A/g, along with a high initial Coulombic efficiency of 90% and excellent rate capability and cyclability in half and full cells. Moreover, the sodium energy reaction kinetics and mechanism of FeP@C are systematically studied. The present work offers a rational design and construction of high-capacity anode materials for high-energy–density Na-ion batteries. [ABSTRACT FROM AUTHOR]

The plateau‐type sodium titanate with suitable sodiation potential is a promising anode candidate for high safe and high energy density of sodium‐ion batteries (SIBs). However, the poor initial Coulombic efficiency (ICE) and cyclic instability of sodium titanate are attributed to the unstable interfacial structure along with the decomposition of electrolytes, resulting in the continuous formation of solid electrolyte interface (SEI) film. To address this issue, a chemical grafting method is developed to fabricate a highly stable interface layer of inert Al2O3 on the sodium titanate anode, rendering the high ICE and excellent cycling stability. Based on theoretical calculations, NaPF6 are more likely adsorption on the Al2O3 surface and produce sodium fluoride. The formation of a thin and dense SEI film with rich sodium fluoride achieves the low interfacial resistances and charge‐transfer resistances. Benefitting from our design, the obtained sodium titanate exhibits a high ICE from 67.7 % to 79.4 % and an enhanced reversible capacity from 151 mAh g−1 to 181 mAh g−1 at 20 mA g−1, along with an increase in capacity retention from 56.5 % to 80.6 % after 500 cycles. This work heralds a promising paradigm for rational regulation of interfacial stability to achieve high‐performance anodes for SIBs. [ABSTRACT FROM AUTHOR]

This contribution provides a thorough examination of the structural characteristics of pyrochlore-type lanthanide titanates and zirconates Ln2Ti2O7 and Ln2Zr2O7, across various length scales. This paper also examines their processing, interesting physical properties (electrical, magnetic, and thermal characteristics), and responses to high pressure and ion irradiation. Brief sections on the elemental oxides' crystal chemistry, pertinent phase diagrams, and energetics of defect formation are also provided. Pyrochlore-type Ln2Ti2O7 and Ln2Zr2O7 stand out as truly multifunctional materials. Moreover, they have emerged as fascinating materials due to magnetic geometrical frustration, arising from the ordering of magnetic Ln3+ and non-magnetic Ti4+ (or Zr4+) cations into separate, interpenetrating lattices of corner-sharing tetrahedra. This results in a diverse array of exotic magnetic ground states, such as spin-ice (e.g., Dy2Ti2O7 or Ho2Ti2O7) or quantum spin ice (e.g., Tb2Ti2O7), observed at both low and room temperatures. They also exhibit varied electrical and electrochemical characteristics. Some members such as Gd2Zr2O7, function as fast ion conductors with a conductivity (σ) of ≈10−2 S·cm−1 at 800 °C and activation energy (Ea) ranging from 0.85 to 1.52 eV, depending on the degree of structural disorder. Others, such as Gd2TiMoO7, are mixed ionic-electronic conductors with σ ≈ 25 S·cm−1 at 1000 °C, making them promising candidate materials for applications in energy conversion and storage devices and oxygen separation membranes. Their exceptionally low thermal conductivity (e.g., κ ∼ 1.1–1.7 W·m−1·K−1 between 700 and 1200 °C for Ln2Zr2O7), close to the glass-like lower limit of highly disordered solids, positions them as valuable materials for thermal barrier coatings. They can also effectively accommodate actinides (e.g., Pu, Np, Cm, Am) in solid solutions and sustain prolonged exposure to radiation due to alpha-decay events, while preserving the integrity of the periodic atomic structure. Proposed as major components in actinide-bearing ceramics, they contribute to the long-term immobilization and disposal of long-lived waste radionuclides from nuclear programs. Some of these properties are displayed simultaneously, opening avenues for new applications. Despite the wealth of data available in the literature, this review highlights the need for a better understanding of order/disorder processes in pyrochlore-type materials and the influence of the structural length scale on their physical and chemical properties. Recent experimental evidence has revealed that pyrochlore short-range structure is far more complex than originally thought. Moreover, pyrochlore local structure is now believed to include short-range, lower symmetry, ordered domains, such as the orthorhombic weberite-type of structure. Notably, short- and long-range structures appear decoupled across different length scales and temperature regimes, and these differences persist even in well-ordered samples. We believe that the pyrochlore structure offers a unique opportunity for examining the interplay between chemical composition, defect chemistry, and properties. [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]

Solid oxide electrolysis cell (SOEC) is a potential technology for converting the principal greenhouse gas, carbon dioxide (CO2), into carbon monoxide (CO) by employing renewable energy. SOECs have great potential, including high‐energy efficiency, fast electrode kinetics, and competitive cost; however, this technology still has challenges in developing highly active, robust CO2 cathode electrocatalysts. In this work, we report the Ni‐doped lanthanum strontium calcium titanate (La0.20Sr0.25Ca0.45Ni0.05Ti0.95O3−δ) cathode for application as the cathode of CO2 electrolysis with gadolinia‐doped ceria (Gd0.1Ce0.9O1.95) electrolyte in SOEC. The exsolution of Ni nanoparticles is achieved by a simple in situ growth method at 800 °C. The Ni doping in LSCT significantly improved the electrochemical activity of the catalyst by increasing oxygen vacancies, and the Ni metallic nanoparticles can afford much more active sites for CO2 reduction. The CO2 electrolysis mechanism is studied by the distribution of relaxation time analysis of impedance spectroscopy. Ni‐LSCT renders a higher activity for electrolysis of CO2 with an exceptionally high reduction current density of 3.89 A cm−2 at 2.5 V potential applied and 800 °C temperature with GDC (Gd0.1Ce0.9O1.95) electrolyte. Ni doping is a crucial factor in controlling the electrochemical performance and catalytic activity in SOEC and GDC electrolytes, which is further helped by the high ionic conductivity. [ABSTRACT FROM AUTHOR]

Rescuing dental implants from plaque‐induced infection and implementing effective plaque control methods in a limited oral environment pose challenges for modern dentistry. To address this issue, Al ion doped strontium titanate/titanium dioxide nanotubes (Al‐SrTiO3/TiO2 nanotubes, Al‐STNT) are designed as an ultrasound‐responsive nanocoating immobilized on the Ti implant surface. Introducing Al3+ ions into the inorganic sonosensitive SrTiO3/TiO2 heterojunction induces oxygen vacancies and disrupts the lattice of SrTiO3. By overcoming the bandgap barrier through ultrasonic stimulated piezoelectric effect, Al‐STNT produces more reactive oxygen species (ROS). In the sonodynamic therapy (SDT) process, stimulus on Al‐STNT induces abundant ROS efficiently disrupting the bacteria biofilm and inhibiting biofilm metabolism. Moreover, the specific nanoscale SrTiO3 coating endows dental implants with osteogenic activity, facilitating the formation of rigid osseointegration between the implant surface and alveolar bone. By mimicking human dental implants in rats, Al‐STNT demonstrates optimal postimplant osseointegration while retaining its antibacterial ability as a sonosensitizer. Thanks to the portability of the ultrasound instrument and the stability of implant‐based sonosensitizer, this strategy presents an attractive option for patients to self‐treat and secure the long‐term success of their implants. [ABSTRACT FROM AUTHOR]

In this study, 2D/2D ZnIn 2 S 4 /Bi 4 Ti 3 O 12 nanoplate heterojunctions were synthesized to alter the Bi 4 Ti 3 O 12 morphology, modulate the bandgap of Bi 4 Ti 3 O 12 , and enhance the utilization of light. The hydrogen production rate of ZnIn 2 S 4 /Bi 4 Ti 3 O 12 nanoplate with the optimal ratio reaches 27.50 mmol/h g−1. [Display omitted] Improving the separation efficiency of photogenerated carriers plays an important role in photocatalysis. In this study, two-dimensional (2D)/2D zinc indium sulfide (ZnIn 2 S 4)/bismuth titanate (Bi 4 Ti 3 O 12) nanoplate heterojunctions were synthesized to alter the Bi 4 Ti 3 O 12 morphology, modulate the bandgap of Bi 4 Ti 3 O 12 , and enhance the utilization of light. Meanwhile, the construction of the S-scheme heterojunction establishes an internal electric field at the ZnIn 2 S 4 /Bi 4 Ti 3 O 12 heterojunctions interface and achieves the spatial separation of photogenerated charges. The hydrogen production rate of ZnIn 2 S 4 /Bi 4 Ti 3 O 12 nanoplate with the optimal ratio reaches 27.50 mmol h−1 g−1, which is 1.5 times higher than that of ZnIn 2 S 4 /Bi 4 Ti 3 O 12 nanoflower (18.28 mmol h−1 g−1) and 2.4 times higher than that of ZnIn 2 S 4 (11.69 mmol h−1 g−1). The apparent quantum efficiency of ZnIn 2 S 4 /Bi 4 Ti 3 O 12 nanoplate reached 57.9 % under a single wavelength of light at 370 nm. This work provides insights into the study of new materials for photocatalytic hydrogen production. [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]

This study presents an innovative method for synthesizing β‐amino carbonylated compounds, specifically 2‐[phenyl(phenylamino)methyl] cyclohexanone, achieving high conversions and diastereomeric ratios. Using trypsin or α‐chymotrypsin in both free and immobilized forms on titanate nanotubes (NtsTi), synthesized through alkaline hydrothermal methods, successful immobilization yields were attained. Notably, α‐chymotrypsin, when free, displayed a diastereoselective synthesis of the anti‐isomer with 97 % conversion and 16 : 84 (syn : anti) diastereomeric ratio, which slightly decreased upon immobilization on NtsTi. Trypsin, in its free form, exhibited diastereoselective recognition of the syn‐isomer, while immobilization on NtsTi (trypsin/NtsTi) led to an inversion of diastereomeric ratio. Both trypsin/NtsTi and α‐chymotrypsin/NtsTi demonstrated significant catalytic efficiency over five cycles. In conclusion, NtsTi serves as an effective support for trypsin and α‐chymotrypsin immobilization, presenting promising prospects for diastereoselective synthesis and potential industrial applications. Furthermore, it offers promising prospects for the diastereoselective synthesis of 2‐[phenyl(phenylamino)methyl] cyclohexanone through multicomponent Mannich reaction and future industrial application. [ABSTRACT FROM AUTHOR]

In this study, TiO2/P, K-containing grapefruit peel biochar (TiO2/P, K-PC) composites were synthesized in situ biomimetically using grapefruit peel as the bio-template and carbon source and tetrabutyl titanate as the titanium source. This was achieved using the two-step rotary impregnation–calcination method. Adjusting the calcination temperature of the sample in an air atmosphere could regulate the mass ratio of TiO2 to carbon. The prepared samples were subjected to an analysis of their compositions, structures, morphologies, and properties. It demonstrated that the prepared samples were complexes of anatase TiO2 and P, K-containing carbon, with the presence of graphitic carbon. They possessed a unique morphological structure with abundant pores and a large surface area. The grapefruit peel powder played a crucial role in the induction and assembly of TiO2/P, K-PC composites. The sample PCT-400-550 had the best photocatalytic activity, with the degradation rate of RhB, MO, and MB dye solutions reaching more than 99% within 30 min, with satisfactory cyclic stability. The outstanding photocatalytic activity can be credited to its unique morphology and the efficient collaboration between TiO2 and P, K-containing biochar. [ABSTRACT FROM AUTHOR]

Halide perovskite Cs3Bi2Br9 (CBB) has excellent potential in photocatalysis due to its promising light-harvesting properties. However, its photocatalytic performance might be limited due to the unfavorable charge carrier migration and water-induced properties, which limit the stability and photocatalytic performance. Therefore, we address this constraint in this work by synthesizing a stable halide perovskite heterojunction by introducing hydrogen titanate nanosheets (H2Ti3O7-NS, HTiO-NS). Optimizing the weight % (wt%) of CBB enables synthesizing the optimal CBB/HTiO-NS, CBHTNS heterostructure. The detailed morphology and structure characterization proved that the cubic shape of CBB is anchored on the HTiO-NS surface. The 30 wt% CBB/HTiO-NS-30 (CBHTNS-30) heterojunction showed the highest BnOH photooxidation performance with 98% conversion and 75% benzoic acid (BzA) selectivity at 2 h under blue light irradiation. Detailed optical and photoelectrochemical characterization showed that the incorporating CBB and HTiO-NS widened the range of the visible-light response and improved the ability to separate the photo-induced charge carriers. The presence of HTiO-NS has increased the oxidative properties, possibly by charge separation in the heterojunction, which facilitated the generation of superoxide and hydroxyl radicals. A possible reaction pathway for the photocatalytic oxidation of BnOH to BzH and BzA was also suggested. Furthermore, through scavenger experiments, we found that the photogenerated h+, e− and •O2− play an essential role in the BnOH photooxidation, while the •OH have a minor effect on the reaction. This work may provide a strategy for using HTiO-NS-based photocatalyst to enhance the charge carrier migration and photocatalytic performance of CBB. [ABSTRACT FROM AUTHOR]

This paper thoroughly examines lanthanum-doped lead titanate (PbLaxTi(1−0.75x)O3), a perovskite-based ceramic material, focusing on its structural properties, vibrational behavior, and radiation shielding capabilities. Using advanced techniques like X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM), we explore the intricate relationship between lanthanum doping levels and material properties. Additionally, we assess its radiation shielding potential through metrics. Computational approaches employing the FLUKA code help evaluate theoretical values. Our findings reveal that increasing lanthanum concentration alters crystal atom arrangement, influences vibrational patterns, and enhances radiation shielding effectiveness. Increasing lanthanum concentration resulted in a maximum 7.55% rise in the mass attenuation coefficient (MAC) at 0.059 MeV. The half-value layer (HVL) decreased by 4.68% at 1.33 MeV, and the mean free path (MFP) decreased by 5.78% at 1.41 MeV with increased lanthanum ratio. Moreover, the radiation protection efficiency (RPE) increased from 30.7779 to 32.67442% at 0.059 MeV as lanthanum content increased. These findings offer valuable insights into material characteristics and suggest potential applications in enhancing radiation shielding for medical and industrial purposes. This comprehensive analysis provides practical insights for potential applications, particularly in medical or industrial radiation protection. The data-driven approach here paves the way for future research at the intersection of data science and material science, advancing material design and understanding doped perovskite materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Tin dioxide (SnO 2) is a promising alternative material to graphite anode, but the large volume change induced electrode pulverization issue has limited its application in lithium-ion batteries (LIBs). In contrast, titanium dioxide (TiO 2) anode shows high structure stability upon lithium insertion/extraction, but with low specific capacity. To overcome their inherent disadvantages, combination of SnO 2 with TiO 2 and highly conductive carbon material is an effective way. Herein, we report a facile fabrication method of carbon-coated SnO 2 /TiO 2 nanowires (SnO 2 /TiO 2 @C) using tin titanate nanowires as precursor, which are prepared by reacting SnCl 2 ·2H 2 O with layered sodium titanate (Na 2 Ti 3 O 7) nanowires in the aqueous solution though the ion exchange between Sn2+ and Na+. After annealing under argon atmosphere, the hydrothermally carbon-coated tin-titanate nanowires decompose, forming a unique hybrid structure, where ultrafine SnO 2 nanoparticles are uniformly embedded within the TiO 2 substrate with carbon coating. Consequently, the SnO 2 /TiO 2 @C nanowires demonstrate excellent lithium storage capacity with high pseudocapacitance contribution, excellent reversible capacity, and long-term cycling stability (673.7/510.5 mAh/g at 0.5/1.0 A/g after 250/800 cycles), owing to the unique hybrid structure, as the well-dispersion of ultra-small SnO 2 within TiO 2 nanowire substrate with simultaneous carbon coating efficiently suppresses the volume changes of SnO 2 , provides abundant reactive sites for lithium storage, and enhances the electrical conductivity with shortened ion transport distance. [ABSTRACT FROM AUTHOR]

The partial substitution of Bi site by Tm ion makes new 4 f and 4 d energy levels below the CB, which can capture and store electrons in shallow traps, synchronously two-dimensional nanoplates of Bi 4 Ti 3 O 12 can transform into ultrathin nanosheets after incorporating Tm ions, thanks to the lower crystal surface energy. [Display omitted] In this study, we prepared two-dimensional Bi 4 Ti 3 O 12 nanosheets doped with rare earth ions. The experimental results show that Bi 4- x Tm x Ti 3 O 12 exhibits the highest reduction performance among various rare earth doped Bi 4 Ti 3 O 12 materials, with a CO yield of 7.25 μmol g−1h−1. Furthermore, a delayed reaction in Bi 3.97 Tm 0.03 Ti 3 O 12 is observed upon a cessation of light irradiation. Theoretical calculations reveal that the introduction of Tm ion not only reduces the surface energy of (0 0 1) plane and make it preferential growth in Bi 4 Ti 3 O 12 , but also brings the intervening energy level of Tm ion (4 f and 4 d mixed orbital), which is closer to the conduction band of Bi 4 Ti 3 O 12 and facilitates charge carrier accumulation in trap states. The electrons retained in the shallow traps promote the hysteresis reaction following a cessation of illumination. This work provides further insights into elucidating precise reduction reaction mechanisms underlying rare earth dopant on photocatalysts. This research provides enhanced insights into unraveling the precise reduction reaction mechanisms influenced by rare earth dopants in photocatalysts. [ABSTRACT FROM AUTHOR]

Inline (or in situ) photon density wave spectroscopy was used to monitor the disintegration of secondary titania particles into their primary particles. Photon density wave spectroscopy can be applied to determine the reduced scattering coefficient μs′$\mu _{\mathrm{s}}^{\prime}$ of a dispersion without dilution or calibration, and thus enables process analysis in materials that are usually unsuitable for established particle characterization techniques. In this work, amorphous titania particles were precipitated from tetraethyl orthotitanate in ethanol by addition of water in presence of different alkali metal salts (NaCl, KCl, CsCl, K2SO4) with concentrations between 0 and 1.6 mM. The present results suggest that the synthesized titania secondary particles disintegrate into their primary particles if the electrostatic repulsion between the primary particles is promoted. This can be achieved by an increased alkali chloride concentration in the synthesis or by addition of larger alkali metal ions. In contrast, the particles are only weakly charged upon addition of sulfate ions, and the disintegration stops. The conclusions drawn from photon density wave spectroscopy results are supported by gravimetric determination of the particle yield, dynamic light scattering measurements, zeta‐potential measurements, and electron micrographs. Additionally, the disintegration was driven to completion by addition of hydrochloric acid to create a transparent suspension of titania primary particles as small as 4.7 nm. [ABSTRACT FROM AUTHOR]

Titanates are one of promising sorbents for toxic heavy metal ions and radionuclides due to various chemical formulas and crystal structures, and their functional properties. Herein, we present a unique seaweed-like sodium titanate mat (SST) with randomly distributed layered sodium dititanate nanofibers synthesized by a simple hydrothermal process. We focused on the effect of NaOH concentration during the hydrothermal process on crystallographic properties and investigated the synthesis conditions for SST. Furthermore, Sr2+ sorption properties of SST and related titanates, which were synthesized by hydrothermal process, was studied by batch tests. SST, which consist of a dititanate phase, was synthesized at 10 mol/L NaOH concentration and trititanate phase was formed when the NaOH concentration was increased to 15 mol/L. The SST showed a high ion-exchange selectivity of Sr2+ against H+ and a high maximum sorption capacity (2 mmol/g), compared with the case of trititanate phase (0.49 mmol/g), which shows the precipitation of SrCO3. This was presumably due to the difference of crystal structure of two titanates. This study demonstrates that the design of the crystal structure is important for controlling the sorption mechanism of sorbents for water treatment. [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]

Recently, a new class of portable self‐powered electronic systems is developed that utilizes highly efficient hybrid nanogenerators that convert mechanical energy into electricity to power various sensors/small‐scale electronics. This article proposes aluminum titanate (Al2TiO5) microparticles (AlT MPs) loaded poly‐glucosamine (PGA) composite film‐based high‐performance hybrid nanogenerators (HNG) employed as a self‐powered sensor for signal indication and as an intruder sensing platform. Initially, AlT MPs are synthesized and various concentrations are loaded into PGA. HNGs are fabricated using composite films/ polydimethylsiloxane, and Al as the positive/negative triboelectric layers and electrode film, respectively. The fabricated HNGs operate in the contact‐separation mode and their produced electrical outputs are comparatively studied to determine the most suitable AlT concentration. The optimized HNG produces the highest electrical output of ≈211 V, ≈5.5 µA, and 79.5 µC/m2. The optimized HNG is employed as a biomechanical energy harvester to scavenge energy from various biomechanical movements and power portable electronics utilizing the developed highly efficient power management circuit. Thereafter, multiple HNGs are utilized to fabricate a self‐powered wireless sensing system and real‐time intruder sensing platform. The proposed highly efficient HNG‐based self‐powered wireless sensing platform is a promising technology that can be used on a large scale in various applications. [ABSTRACT FROM AUTHOR]

To address the dilemma of the stiffness and toughness properties of high-density polyethylene (HDPE) composites, titanate coupling agent-treated CaCO3 nanoparticles (nano-CaCO3) and ethylene–octene copolymer (POE) were utilized to blend with HDPE to prepare ternary nanocomposites via a two-sequence-step process. Meanwhile, a one-step process was also studied as a control. The obtained ternary nanocomposites were characterized by scanning electron microscopy (SEM), Advanced Rheometrics Expansion System (ARES), Dynamic Mechanical Analysis (DMA), wide-angle X-ray diffraction analysis (WXRD), and mechanical test. The SEM results showed one or two CaCO3 nanoparticles were well-encapsulated by POE and were uniformly dispersed into the HDPE matrix to form a core–shell structure of 100–200 nm in size by the two-step process, while CaCO3 nanoparticles were aggregated in the HDPE matrix by the one-step method. The result of the XRD showed that the nano-CaCO3 particle played a role in promoting crystallization in HDPE nanocomposites. Mechanical tests showed that the synergistic effect of both the POE elastomer and CaCO3 nanoparticles should account for the balanced performance of the ternary composites. In comparison with neat HDPE, the notched impact toughness of the ternary nanocomposites of HDPE/POE/nano-CaCO3 was significantly increased. In addition, the core–shell structure absorbed the fracture impact energy and prevent further propagation of micro-cracks, thus obtaining a higher notched Izod impact strength. [ABSTRACT FROM AUTHOR]

Outstanding materials and novel device structures are key factors in satisfying the increasing demand for energy storage. Li‐ion capacitors, as one typical model of asymmetric supercapacitors, benefit from the battery's ultrahigh specific energy and supercapacitor's superlarge specific power to meet the balanced electrochemical energy storage requirements. The inherent and irreplaceable advantages make spinel lithium titanate an optimal candidate for power batteries and Li‐ion capacitors. However, upstream market volatility, including price spikes and supply shortages, tremendously threatens spinel lithium titanate's production, sale, and application. Lithium hydroxide hydrate is an alternative raw material to synthesize spinel lithium titanate synthesis, which can help address these concerns. The indirect production path generates high‐quality lithium carbonate as an intermediate product. Spinel lithium titanate is synthesized preferably via another economically and technically more efficient method that skips the isolation step after carboxylation. The electrochemical performance of the resulting spinel lithium titanate is evaluated to be better than that of commercial competitors. The spinel lithium titanate negative electrode‐based lithium‐ion capacitor achieves a specific energy of 89.5 Wh kg−1. These results demonstrate the success of efforts to find a feasible and affordable synthesis route to mitigate market risks. [ABSTRACT FROM AUTHOR]

In this study, a series of rare-earth titanates with the general formula Re2TiO5 (Re = Er, Tm, Yb, and Lu) were synthesized and their microwave dielectric properties were reported. The impact of differences in rare-earth cation radii on the structure and dielectric properties was systematically analyzed. The findings indicated that ceramics of Re2TiO5 (Re = Er, Tm, Yb, and Lu) were crystallized into a cubic structure with space group Fd-3m, as confirmed by Rietveld refinement and selected-area electron diffraction patterns. The rare-earth elements were analyzed for their impact on microwave dielectric properties, considering factors such as ionic polarizability, packing fraction, and bond valence theory. The resulting materials exhibited excellent microwave dielectric properties with a low permittivity (6.95-7.21), high-quality factors (19 451-20 115 GHz), and low positive temperature coefficient of resonance frequency (19.34-20.90 ppm/°C). The origin of low permittivity was elucidated through the analysis of bond length, X-ray photoelectron spectroscopy, and impedance spectroscopy. This series of titanates exhibited unusually low permittivity characteristics in the microwave frequency range, which couldmeet the low signal transmission delay requirements in wireless communication. [ABSTRACT FROM AUTHOR]

Wide bandgap semiconductor-based photocatalysts are usually limited by their low solar energy conversion efficiency due to their limited absorption solar wavelength, their rapid surface recombination of the photogenerated electron–hole pairs, and their low charge-carrier mobility. Here, we report a novel stepwise solution synthesis for achieving a new photocatalytic core–shell consisting of a titanate nanowire/reduced graphene oxide shell (or titanate/rGO) 1D-nanocomposite. The new core–shell nanocomposite maximized the specific surface area, largely reduced the charge transfer resistance and reaction energy barrier, and significantly improved the absorption of visible light. The core–shell nanocomposites' large on/off current ratio and rapid photo-responses boosted the photocurrent by 30.0%, the photocatalysis rate by 50.0%, and the specific surface area by 16.4% when compared with the results for the pure titanate nanowire core. Our numerical simulations support the effective charge separation on the new core–shell nanostructure, which can help further advance the novel photocatalysis. [ABSTRACT FROM AUTHOR]

High- Q and temperature-stable ceramics are indispensable in microwave engineering. However, medium-permittivity (ε r ∼ 60, named as K60) microwave dielectric ceramics that meet the above demands are yet to be synthesized. High- Q Ba 4 Sm 9.33 Ti 16.5 Al 2 O 54 (BSTA) and Ca 0.6 Sm 0.27 Ti 0.8 Al 0.27 O 3 (CSTA) ceramics have large resonant frequency temperature coefficients (τ f) with opposite signs. The composites of the two are expected to have good dielectric properties, but there will be obvious diffusion when they are compounded with each other by sintering after directly mixing the raw powder, which would lead to severe deterioration in dielectric properties. In this work, the undesired diffusion can be effectively avoided by stacking two or three ceramic layers together, which are achieved by two methods named adhesive bonding and spark-plasma-sintering (SPS) cofiring. The finite element method (FEM) analysis with COMSOL Multiphysics proposed in this work can precisely predict the microwave dielectric properties of layered ceramics, helping to determine the ratio of different layers to reach near-zero τ f. The adhesive-bonded layered ceramics exhibit excellent dielectric properties: ε r = 62.2, Q × f = 21,400 GHz, and τ f = –0.7 ppm/°C. The SPS-cofired layered ceramics can be fabricated in one time, partially solving the problem of sintering mismatch between different layers, together with superior properties of ε r = 59.8, Q × f = 19,780 GHz, and τ f = –0.6 ppm/°C. These layered ceramics could fill the gap of high- Q and temperature-stable K60 microwave dielectric ceramics. The layer-stacking process and related FEM simulations can be used to design more high- Q and temperature-stable microwave dielectric ceramics and devices. • High- Q , temperature stable K60 ceramics are obtained (Q × f ∼ 20,000 GHz). • The diffraction in the directly-mixing process is thoroughly examined. • FEM simulation can precisely predict the properties of layered ceramics. • SPS-cofiring can partially solve the problem of sintering mismatch. [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]

In this paper, we report on the solvothermal preparation and detailed characterization of pristine and intentionally doped zirconium dioxide (ZrO2) nanocrystals (NCs, ~5 nm) with Eu3+ or Ti4+/Eu3+ ions using alkoxide precursors. The results indicated that the ZrO2 NCs were dominantly of a tetragonal phase (t-ZrO2) with a small proportion of monoclinic ZrO2 (m-ZrO2). The high purity of t-ZrO2 NCs could be synthesized with more Eu3+ doping. It was found that the as-obtained ZrO2 NCs contain some naturally present Ti4+ ions originating from precursors, but were being overlooked commonly, and some carbon impurities produced during synthesis. These species showed distinct photoluminescence (PL) properties. At least two types of Eu3+, located at low- and high-symmetry sites (probably sevenfold and eightfold oxygen coordination), respectively, were demonstrated to build into the lattice structure of t-ZrO2 NCs together. The cationic dopants were illustrated to be distributed non-randomly over the sites normally occupied by Zr, while Ti impurities preferentially occupied the sites near the low-symmetry site of Eu3+, yielding efficient energy transfer from the titanate groups to the neighboring Eu3+. Luminescence nanothermometry could measure temperature in a non-contact and remote way and could find great potentials in micro/nano-electronics, integrated photonics, and biomedicine. On the basis of the dual-emitting combination strategy involving the white broadband CT (Ti3+→O−) emissions of the titanate groups and red sharp Eu3+ emissions, t-ZrO2:Eu3+ nanophosphors were demonstrated to be ratiometric self-referencing optical thermometric materials, with a working range of 130–230 K and a maxima of relative sensitivity of ~1.9% K−1 at 230 K. [ABSTRACT FROM AUTHOR]