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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]

In this work, an enhanced-performance deep-ultraviolet (DUV) photodetector based on a Ga2O3/lead zirconate titanate (Pb(Zr0.52Ti0.48)O3, PZT) p-n heterojunction is fabricated and characterized for the first time. Compared to a Ga2O3-based device, the heterojunction device achieved a lower dark current of 2.7 10−11 A, a higher photo- to dark-current ratio of 2 103, a higher responsivity of 5.5 mA W−1, a larger specific detectivity of 2.6 1011 Jones and a higher external quantum efficiency of 2.7% at −2 V under 254 nm UV light illumination with an intensity of 500 μW cm−2. The p-PZT/n-Ga2O3 was confirmed to be a potential candidate for the construction of DUV photodetectors with enhanced sensing performance. [ABSTRACT FROM AUTHOR]

Numerical simulations have been performed to study hydrogen interstitial diffusion and ferroelectric degradation in lead titanate films. The computational method consists of two parts: hydrogen diffusion property calculations using density functional theory (DFT) and ferroelectric property calculations using molecular dynamics (MD) simulations. The hydrogen interstitial diffusion path and the activation energy have been obtained using DFT calculations. With the obtained diffusion properties, the distributions of hydrogen impurities have been calculated using Fick's second law and used as input to MD simulations, with various diffusion times and hydrogen surface concentrations. It has been found that magnitudes of remnant polarization and coercive electric fields decrease with increasing the diffusion time and the hydrogen surface concentration. The distribution of hydrogen impurities is another critical factor to ferroelectric responses. Compared to a uniform distribution of hydrogen impurities, the nonuniform distribution diminishes the ferroelectric properties more severely. A heavily defective region due to the nonuniform hydrogen distribution reduces the effective film thickness and induces the in-plane ferroelectric domain formations. [ABSTRACT FROM AUTHOR]

The use of lithium titanate (Li4Ti5O12, LTO) for the negative electrode in lithium ion batteries has attracted enormous attention owing to its fast charging capability, high power, safe operating voltage window and stable structure ("zero strain") during cycling. Researchers have investigated the formation of the solid electrolyte interface (SEI) of the LTO electrode, which prevents gassing issue and leads to longer cycle life. In this study, the solid-state diffusion property of LTO at room temperature was characterized using AC impedance spectroscopy at different states of charge (SOC) during charge and discharge to reveal the dependency of the lithium diffusion coefficient on SOC. Meanwhile the formation and growth of the solid electrolyte interface (SEI) on the LTO electrode using an electrolyte containing Silatronix OS3® additive were investigated using X-ray photoelectron spectroscopy (XPS). The composition of the SEI and its evolution due to cycling with the OS3® additive was compared to that with a commercial electrolyte. Half-cell coin cells of LTO vs lithium metal were formed and cycled at room temperature for over 200 cycles, where the resistance increase, as measured by impedance spectroscopy, is correlated to the SEI growth. Electrode samples were analyzed in the pristine state, after formation, and after 200 cycles. XPS results showed that a thin layer of SEI is formed during the first two formation cycles and the composition of the SEI on the surface of the LTO electrode varied with increasing cycle number. Based on the escape depths of Ti 3 s and Ti 2p regions, the SEI after formation is thicker than 5.5 nm but is less than 7.0 nm for both the OS3® and A7 electrolytes. Based on Ar-ion depth profiling, the SEI thickness in terms of the equivalent thickness of SiO2 after 200 cycles in coin cell configuration is estimated to be near 14 nm for both the OS3® and A7 electrolytes. A much higher fluorine content (F 1s peak) was found in the SEI formed with the OS3® electrolyte than the SEI formed with the commercial A7 electrolyte. [ABSTRACT FROM AUTHOR]

Gassing at elevated temperature is the main reason for the performance degradation of lithium titanate (Li4Ti5O12, LTO) batteries. In this study, an in-situ device was developed and used to study on-line the transient gassing of custom-made 4.5Ah LTO/NCM pouch batteries at 1C cycling at 55°C. The gas volume and internal pressure of the batteries were recorded on-line for 1000 h, and the composition of the gas components at different times was also analyzed by on-line gas chromatography. The results show that H2 and CO2 are the main gas components. The H2 percentage decreases, while the CO2 percentage increases gradually during the process of gassing. According to the rate-controlling step of gassing from H2 formation reaction to CO2, a stage-by-stage mixed gassing mechanism is proposed, where the water decomposition is dominant in the initial stage and solvent decomposition is dominant in the subsequent stage. The gassing of LTO batteries aged at 55°C was studied on-line at different states of charge (0%, 50%, 100% SOC). The results show that the volume and composition of the gas are essentially independent of the SOC of batteries and that formation of SEI at LTO interface is the main reason for the gassing rate reduction when aged and cycled (final phase) at 55°C. [ABSTRACT FROM AUTHOR]

In this work, we report on the fabrication of continuous and uniform thin films by a solid state reaction. The fabrication of spinel Li4Ti5O12 thin films was demonstrated by solid state reaction between TiO2 and Li2CO3 stacked-layers upon thermal annealing. The TiO2 layer was prepared by physical vapor deposition or atomic layer deposition, whereas the Li2CO3 layer was deposited by chemical solution deposition or atomic layer deposition. The solid state reaction and obtained material properties were investigated on planar substrates. It was found that continuous films with crystalline and stoichiometric Li4Ti5O12 can be formed by solid state reaction at temperatures higher than 650°C. The prepared films exhibited Li-ion intercalation characteristics for Li4Ti5O12 spinel with the typical flat plateau at 1.55 V (vs Li+/Li) for both charging and discharging. The theoretical capacity of 612 mAh cm-3 was obtained at slow charging rate of 0.1 C with still 45% capacity attainable at 20 C. Interestingly, it was found that the kinetics is strongly dependent on the current collector substrate used. A TiN substrate provided faster Li4Ti5O12 electrode kinetics than a Pt substrate, despite a thin anatase interlayer at the TiN/TiO2/ Li4Ti5O12 interface, showing the importance of interface or work function matching for high rate lithiation/delithiation performance. In addition, the potential of conformal Li4Ti15O12 thin films on high aspect ratio structures was demonstrated. [ABSTRACT FROM AUTHOR]

The effect of the interaction between A-site deficient La-substituted SrTiO3(LST) and 1CeO2--10Sc2O3--89ZrO2 (ScSZ) on the electrochemical performance of SOFC was investigated. (L0.25Sr0.75)0.9TiO3 (LST-0.9) with perovskite phase and (L0.25Sr0.75)0.85TiO3 (LST-0.85) with perovskite phase and little rutile TiO2phase were produced. ScSZ electrolyte-supported SOFCs with LST-0.9/ScSZ composite anode and LST-0.85/ScSZ composite anode sintered at different temperature (1000 and 1200°C) were respectively performed at 1000°C in humidified H2. Rapid electrochemical performance degradation occurred during the initial few hours of the test for the cells with LST-0.9/ScSZ composite anode and LST-0.85/ScSZ composite anode sintered at 1200°C. Inter-diffusion processes of Zr and Sc from ScSZ into LST-0.9 and Ti from LST-0.85 into ScSZ occurred during anode preparation processes and the performance test were respectively considered as dominant degradation mechanism for the cells with LST-0.9/ScSZ composite anode and LST-0.85/ScSZ composite anode. Details of the degradation mechanism for the cells with two kinds of anodes were discussed respectively. [ABSTRACT FROM AUTHOR]

CdS nanoparticles were confined within titanate nanotubes (TNTs) by an ion-exchange reaction and a subsequent sulfurization process. Prior to the ion-exchange reaction, the exterior surfaces of the TNTs were modified by a silane coupling agent to make CdS nanoparticles selectively deposit on the inner wall. The composites were characterized by high-resolution transmission electron microscopy, powder x-ray diffraction, inductively coupled plasma atomic emission spectrometry, N2 adsorption–desorption and UV–vis absorption spectra. The results confirm that CdS in the range of 2–3 nm in diameter are confined within the inner cavity of the TNTs. CdS confined within TNTs shows a significant blue-shift of the absorption band edge compared with CdS nanoparticles deposited on the exterior surface of TNTs. Also the TNTs-confined CdS composite exhibits enhanced photocatalytic activity and photostability for hydrogen evolution under visible light illumination due to the quantum size effect of CdS as a result of the spatial confinement effect of the TNTs. [ABSTRACT FROM AUTHOR]

Sodium bismuth titanate Na0.5Bi0.5TiO3 (NBT) single crystal doped with Nd3+ was grown by a top-seeded solution growth method. Powder x-ray diffraction revealed a pure perovskite structure with the rhombohedral phase. We found that the dielectric and ferroelectric properties were enhanced by the Nd3+ dopant. After poling along the [111] direction, transmittance was enhanced dramatically. The Sellmeier dispersion equation and energy band gaps were obtained. The absorption band around 808 nm has high full-width at half-maximum and large absorption cross-section, which is suitable for AlGaAs diode-laser pumping. A strong emission transition band of Nd3+ at around 1066 nm was observed; a long radiation lifetime 324µs shows a low quenching effect. These results indicate that Nd3+-doped NBT crystal could be applied in photonic or integrated optoelectronic devices as a multi-functional crystal. [ABSTRACT FROM AUTHOR]

A sol-gel method was applied to add a chemically protective lithium titanate (LTO) and/or anatase (TiO2) layer to LiNi0.5Mn1.5O4-δ (LNMO). By TEM imaging, the coating thickness was 5-10 nm or 20-30 nm, depending on the volume of precursor used. Cells were cycled at room temperature and at 55°C. A thin-layer TiO2 coating gives LNMO with a discharge capacity of 113 mAh/g when cycled between 3.4-5.0 V vs. Li+/0 at room temperature (1 C rate), with no capacity fade over the first 100 cycles. At higher temperature, the capacity is similar, with no change in the polarization gap (~50 mV) after 55 cycles. A slight increase in the lattice parameter after cycling hints at oxygen-vacancy formation or transition-metal dissolution. At 10 C rate, bare LNMO showed the highest capacity (87 mAh/g). However, the thinly coated materials showed comparable rate capability. All materials show a similar lithium-ion diffusivity (DLi ~ 10-11 cm²/s, estimated by GITT measurements), but the 10% loss in capacity at 10 C rate for coated samples may be due to differences in electrical conductivity (σ ~ 1.12 x 10-5 S/cm for bare LNMO; 7.15 x 10-6 S/cm for the thicker coated LNMO). [ABSTRACT FROM AUTHOR]

The oxidation state and size of Pt nanoparticles attached to alkali metal titanate nanotubes (MTNTs D M2Ti3O7, M = Li+, Na+, K+, Cs+) via ion exchange (indicated by the added label '-IE') and wet impregnation (indicated by the added label '-IMP') methods varied systematically with the cation of the MTNTs. X-ray photoelectron spectroscopy revealed that the binding energy of Pt was reduced to a low value when the support was changed from LiTNTs to CsTNTs, yielding a Ptδ- oxidation state. Thus, a space charge layer (SCL) was constructed at the interface between the Pt particle and MTNT support; the former carried the negative charge, and the alkali cation and proton in the hydroxyl group of the latter carried the positive charge. Due to a higher M/Ti atomic ratio in MTNTs, a higher electron density accumulated on Pt particles in Pt/MTNTs-IMP than on those in Pt/MTNTs-IE. Sub-ambient temperature temperature-programmed reduction and transmission electron microscopy revealed that because of the difference in reducibility of PtOx/MTNTs, the mean Pt particle size followed the order Pt/CsTNTs > Pt/KTNTs > Pt/NaTNTs > Pt/LiTNTs and Pt/MTNTs-IMP > Pt/MTNTs-IE. DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) showed that owing to its interaction with SCL, cinnamaldehyde adsorbed on Pt mainly through the CDC bond at the Pt-MTNT interfaces, and the small Pt particles in Pt/LiTNTs adsorbed three times more cinnamaldehyde than those in Pt/CsTNTs. Due to the competition between the adsorption of cinnamaldehyde and CDC activation, Pt/KTNT-IMP is the most active Pt/MTNT catalysts, achieving a conversion of 100% in the hydrogenation of cinnamaldehyde at 2 atm and 313 K. The carbonyl stretching of adsorbed cinnamaldehyde was almost unperturbed by adsorption (at 1705 cm-1), suggesting that Ptδ- and the π electrons in the carbonyl group repel each other, so the CHDO group points upward and away from the Pt surface, preventing it from being hydrogenated and causing Pt/MTNTs to exhibit high 3-phenyl propionaldehyde selectivities of 75-80%. [ABSTRACT FROM AUTHOR]

A titanate conversion coating was made on AZ31 magnesium alloys in a titanium chloride and hexafluorosilicic acid solution. The titanate conversion coating formation proceeded via the formation of a porous magnesium hydroxide and fluoride layer. Compact silicon hydroxide and titanium hydroxide were then formed locally on top of the porous layer. The fluorine ion dissociated from hexafluorosilicic acid contributed to the incorporation of magnesium fluoride in the porous layer. Moreover, a pH rise due to hydrogen discharge caused the precipitation of silicon hydroxide and titanium hydroxide. With continued immersion, the porous layer thickened and the coverage of the compact silicon hydroxide and titanium hydroxide proceeded to a larger extent, which, in turn, reduced the corrosion area fraction and enhanced the polarization resistance of the AZ31. However, prolonged immersion resulted in more cracks with larger openings, which reduced the corrosion resistance of the titanate conversion coating. As a result, the titanate conversion coating formed at immediate immersion times provided the best corrosion protection on the AZ31. [ABSTRACT FROM AUTHOR]

The structural, morphological, and dielectric properties of CaCu3Ti4O12 (CCTO) ceramics without and with 10% HfO2 by weight were investigated in this work. The main effect of adding HfO2 on the microstructure was the segregation of HfO2 subgrains within CCTO grains, which consequently causes the inhomogeneous electric structure of the HfO2-modified sample. The HfO2-modified sample presented the much larger dielectric constant than the pure CCTO one, which resulted from HfO2 subgrains' effect as another new origin of the dielectric constant. [ABSTRACT FROM AUTHOR]

The H2Ti3O7 sheet-like products were successfully obtained during the formation process of titanate nanotubes via alkali hydrothermal synthesis. The morphological features and structural characteristics of the sheet-like products were studied systematically. Results indicate that three types of sheet-like structures, including layered structure, multi-layer nanosheets and single-layer nanosheet of titanate H2Ti3O7, were observed. The structural characteristics of these sheet-like products were determined by high-resolution structure analysis. It is found that the top/bottom surface of these sheet-like structures is the (010) plane of H2Ti3O7. [ABSTRACT FROM AUTHOR]

Barium titanate films grown under a H2-rich atmosphere display a high dielectric constant and therefore can be employed as electrolytes in the all-solid-state supercapacitors. This behavior was attributed to the accumulation of protons at the metal-electrolyte interface over a Debye length (capacitive double layer). Electrical measurements were carried Out On hydrogenated layers (BaTiO3:H) and a trilayer stack (BaTiO3/BaTiO3:H/BaTiO3) to study the active defects at the origin of the conduction mechanisms. [ABSTRACT FROM AUTHOR]

Strontium titanate (STO) is a promising candidate as a highk dielectric for dynamic random access memory application. STO thin films are deposited by atomic layer deposition using Sr(tBu3Cp)2, Ti(OMe)4, and H2O as precursors. Growth and saturation behavior of STO and binary oxides are evaluated by ellipsometry thickness measurements. The precursor pulse ratio controls the amount of Sr and Ti inëorporated in STO films. Stoichiometric SrTiO3 is characterized by the lowest crystallization temperature and largest refractive index, density, and dielectric constant. An excess of Ti or Sr results in an increase in the crystallization onset temperature and contraction or expansion of the cubic cell constant of perovskite SrTiO3. Incorporation of more Sr in STO reduces the leakage current density but also increases the capacitanceequivalent thickness. [ABSTRACT FROM AUTHOR]

Hafnium titanate (HTO) films were deposited within a large Hf-Ti compositional range by atomic layer deposition using HfCl4/TiCI4/H2O precursors. The Hf content of the layers is well controlled by the precursor pulse ratio, as indicated by Rutherford backscattering. The saturation conditions of ternary HTOs are different compared to those of the binary oxides. First-principles simulation confirmed the enhancement of the Hf precursor reactivity in the presence of Ti-OH. Growth curves of HTOs showed a good linearity with the number of reaction cycles. A linear correlation between density, quantified by X-ray refiectometry, and composition was observed. X-ray diffraction indicated that the as-deposited films are amorphous up to 500-700°C, depending on the Hf/Ti ratio. The orthorhombic HfTiO4 diffraction lines in the samples (30-64% Hf) annealed at 850°C were observed. For a Hf content higher than 82%, a monoclinic HfO2-like structure was reported. The dielectric constant and leakage current depend on the Ti content, the film crystallinity, and the anneal atmosphere. The postdeposition anneal in O2 is found to have a drastic effect in leakage current density reduction and could be a key for further improvements of HTO electrical properties. [ABSTRACT FROM AUTHOR]

Highly uniformed barium-strontium titanate nanotube arrays were fabricated using a porous anodic aluminum oxide template from a barium-strontium titanate sol-gel solution. Electron microscope results showed that nanotubes with uniform length and diameter were obtained. The diameters and lengths of these nanotubes were dependent on the pore diameter and the thickness of the applied anodic aluminum oxide template. High resolution transmission electron microscopy and the selected-area electron diffraction pattern investigations demonstrated the perovskite structure and the polycrystalline of the fabricated barium-strontium titanate nanotubes. The characterization of the electrical and dielectric properties had also been made. Compared to thin film material, the intrinsic leakage current density is almost the same. Besides, at 30 °C, the dielectric constant and dielectric loss of the fabricated nanotube is 80 and 0.027 at 1 MHz respectively. [ABSTRACT FROM AUTHOR]

Starting from the multiorbital Hubbard model for the t2g-bands of RTiO3 (R = Y, Gd, Sm and La), where all the parameters have been derived from the first-principles electronic structure calculations, we construct an effective superexchange (SE) spin model, by treating transfer integrals as a perturbation. We consider four approximations for the SE interactions: (i) the canonical crystal-field (CF) theory, where the form of the occupied t2g-orbitals is dictated by the CF splitting at each Ti-site and three extensions of the CF theory, namely (ii) the relativistic one, where occupied orbitals are confined within the lowest Kramers doublet obtained from the diagonalization of the CF and relativistic spin-orbit (SO) interactions; (iii) the finite-temperature extension, which considers the effect of thermal orbital fluctuations near the CF configuration on interatomic interactions between the spins; (iv) the many-electron extension, which is based on the diagonalization of the full Hamiltonian constructed in the basis of two-electron states separately for each bond of the system. The main results are summarized as follows. (i) Thermal fluctuations of the orbital degrees of freedom can substantially reduce the value of the magnetic transition temperature. (ii) The relativistic SO coupling is generally responsible for anisotropic and antisymmetric Dzyaloshinsky-Moriya interactions. All interactions are rigorously derived and their implications for the magnetic properties of RTiO3 are discussed. (iii) The CF theory, although applicable for YTiO3 and high-temperature structures of GdTiO3 and SmTiO3, breaks down in the case of LaTiO3. In the latter, the CF splitting is small. Therefore, the many-electron effects in the bonds as well as the relativistic SO interaction start to play an important role. It is argued that the combination of these two effects could be responsible for the AFM character of interatomic correlations in LaTiO3. (iv) The SE interactions in YTiO3 strongly depend on the details of the crystal structure. Crystal distortions in the low-temperature structure tend to weaken the ferromagnetic interactions. [ABSTRACT FROM AUTHOR]

The H[sup+]-sensing behaviors of barium strontium titanate (BST) ultrathin films are reported. The sputtering technique was used to prepare the Ba[sub0.7]Sr[sub0.3]TiO[sub3] ferroelectric structure. To obtain better electrical characteristics for the BST membrane, we characterized electrical properties of the BSTISiO[sub2] thin film for the gate oxides in the metal-oxide-semiconductor devices under different deposition times of 10, 20, and 30 mm using high frequency capacitance-voltage and current-voltage measurements. The pHsensing properties of the stack BST/SiO[sub2] layers were also investigated using capacitance-voltage measurements on the electrolyte! insulator/semiconductor. The results show that BST ultrathin film (<30 nm) still exhibits linear pH sensitivities of approximately 50-58 mV/pH ranging from pH 1 to 11. Besides, the drift rate and temperature dependence of the measured pH sensitivity has also been represented. [ABSTRACT FROM AUTHOR]

This paper reports that the lead zirconate titanate (PZT) piezoelectric composites incorporating zinc oxide nanowhiskers (ZnOw) were prepared by the conventional solid state processing. The whisker-dispersed PZT composites (PZT/ZnOw) presented a significant enhancement in the mechanical properties such as Young's modulus, tensile strength and compressive strength. Especially, the compressive strength increased from 153 MPa for the PZT to 228 MPa for the PZT/ZnOw composites. The reinforcement mechanism in strength of the composites was discussed. The mechanical quality factors of the PZT/ZnOw composites increased considerably, while the piezoelectric constants and electromechanical coupling coefficient decreased slightly. The composites with good electrical and excellent mechanical properties are promising for further applications. [ABSTRACT FROM AUTHOR]

A high-k NdTiO3 gate dielectric was formed in films using Ti added to Nd2O3 film prepared under various Nd metal thicknesses through radio frequency (rf) sputtering and annealed at 700°C. The structural and compositional features of these films were studied through X-ray diffraction and X-ray photoelectron spectroscopy. We found that the NdTiO3 gate dielectric using a 3 nm Nd metal film exhibited a reduced equivalent oxide thickness, interfacial density of states, and hysteresis voltage; it also showed negligible charge trapping under high electric voltage Stress. We attribute this behavior to the high neodymium content in the NdTiO3 film suppressing the formation of interfacial SiO2 and silicate layer at the NdTiO3/Si interface [ABSTRACT FROM AUTHOR]

Nafion-titanate nanotube composites were investigated as electrolytes for proton exchange membrane fuel cells (PEMFCs) operating at high temperature T. With the addition of 5-15 wt % of nanotubes to the ionomer, PEMFC performance can be significantly sustained for T up to 130°C. The polarization curves of PEMFCs using the composite electrolytes reflect a competing effect between an increase in water uptake due to the extremely large surface area of the nanotubes and a decrease in proton conductivity of the composites. [ABSTRACT FROM AUTHOR]

In this study, titanium metal acts as the titanium source to prepare oriented titanate nanotube thin film. The effects of preparation parameters, such as reaction temperature, duration and post-treatment conditions, on the film morphology and stability have been examined. A general formation mechanism for oriented titanate nanotube thin film is proposed on the basis of detailed observations of the products using two-dimensional surface SEM studies and TEM images. The overall formation of titanate nanotubes can be summarized as a sequence of four steps: (a) titanium dissolution and alkali titanate hydrogel formation; (b) alkali titanate hydrogel dissolution, increased TiO2-3 , TiO2(OH)2-2 or TinO2m-2n+m concentration and layered Na2Ti3O7 formation; (c) layered Na2Ti3O7 growth; (d) nanotube formation via Na2Ti3O7 splitting and the multilayer scrolling process. The Na2Ti3O7 lamellar structures split between the (010) planes into nanosheets. [ABSTRACT FROM AUTHOR]

The piezoelectric properties of the (KCe)-substituted sodium bismuth titanate (Na0.5Bi4.5Ti4O15, NBT) piezoelectric ceramics are investigated. The piezoelectric properties of NBT ceramics are significantly enhanced by (KCe) substitution. The Curie temperature Tc, and piezoelectric coefficient dss for the (KCe)-substituted NBT are found to be 663°C, and 27pC/N, respectively. Dielectric and annealing spectroscopy present that the (KCe) co-substituted NBT piezoelectric ceramics possess stable piezoelectric properties. [ABSTRACT FROM AUTHOR]

High-quality nanoscaled fluorine and nitrogen co-doped anatase-phase titanium oxide can be obtained from the conversion of ammonium oxotrifluorotitanate by thermal treatment. The photocatalytic activity of titanium oxide treated at 800°C shows the highest photocatalytic activity and is about 1.31 times of P-25 due to higher fluorine and nitrogen doping. The heterojunction of zinc sulfide/titanium oxide prepared by metallorganic vapor-phase epitaxy shows 1.51 times the photocatalytic activities of commercial P-25. Both nanoscaled titanium oxide and zinc sulfide/titanium oxide heterojunction show a proportional relationship between carrier lifetime and photocatalytic activity. [ABSTRACT FROM AUTHOR]

Highly efficient H2 production from water splitting has been achieved by N-doped titanate nanotubes (N-TNTs) decorated with graphene quantum dots (GQDs) in this work. In order to promote charge carrier transmission at the interface, a facile and environmentally friendly in situ growth method was employed to construct a strongly coupled N-TNT/GQD composite photocatalyst. The results revealed that N atoms were effectively doped into the crystal lattice of the TNTs in the form of both interstitial N and substitutional N, and the GQDs were decorated onto both the inner and outer surfaces of the N-TNTs through the formation of Ti–O–C chemical bonds. Photoelectrochemical measurements proved that, in N-TNT/GQD composite, N-doping can extend light response to the visible-light range, and the coupling with GQDs not only enhanced visible-light absorption, but also promoted interfacial charge carrier transfer. Due to the synergistic effect between N-doping and GQD coupling, the closely integrated N-TNT/GQD composite exhibits a much superior photocatalytic H2 production performance under UV–vis irradiation, being 2.1 times higher than that of pure TNTs. [ABSTRACT FROM AUTHOR]

We review all the published literature and show that there is no experimental evidence for homogeneous tin titanate SnTiO3 in bulk or thin-film form. Instead a combination of unrelated artefacts are easily misinterpreted. The x-ray Bragg data are contaminated by double scattering from the Si substrate, giving a strong line at the 2θ angle exactly where perovskite SnTiO3 should appear. The strong dielectric divergence near 560 K is irreversible and arises from oxygen site detrapping, accompanied by Warburg/Randles interfacial anomalies. The small (4 µC cm−2) apparent ferroelectric hysteresis remains in samples shown to be pure (Sn,Ti)O2 rutile/cassiterite, in which ferroelectricity is forbidden. Only very recent work reveals real bulk SnTiO3, but it possesses an ilmenite-like structure with an elaborate array of stacking faults, not suitable for ferroelectric devices. Unpublished TEM data reveal an inhomogeneous SnO layered structured thin films, related to shell–core structures. The harsh conclusion is that there is a combination of unrelated artefacts masquerading as ferroelectricity in powders and ALD films; and only a trace of a second phase in PLD film data suggests any perovskite content at all. The fact that x-ray, dielectric, and hysteresis data all lead to the wrong conclusion is instructive and reminds us of earlier work on copper calcium titanate (a well-known boundary-layer capacitor). [ABSTRACT FROM AUTHOR]

Soft polyethylene oxide (PEO)/chitosan mixtures, reinforced with hard titanate nanotubes (TiNTs) by co-precipitation from aqueous solution, have been used to produce compact coatings by the ‘drop-cast’ method, using water soluble PEO polymer and stable, aqueous colloidal solutions of TiNTs. The effects of the nanotube concentration and their length on the hardness and modulus of the prepared composite have been studied using nanoindentation and nanoscratch techniques. The uniformity of TiNT dispersion within the polymer matrix has been studied using transmission electron microscopy (TEM). A remarkable increase in hardness and reduced Young’s modulus of the composites, compared to pure polymer blends, has been observed at a TiNT concentration of 25 wt %. The short (up to 30 min) ultrasound treatment of aqueous solutions containing polymers and a colloidal TiNT mixture prior to drop casting has resulted in some improvements in both hardness and reduced Young’s modulus of dry composite films, probably due to a better dispersion of ceramic nanotubes within the matrix. However, further (more than 1 h) treatment of the mixture with ultrasound resulted in a deterioration of the mechanical properties of the composite accompanied by a shortening of the nanotubes, as observed by the TEM. [ABSTRACT FROM AUTHOR]

Titanate nanotubes are promising materials for Li-ion battery anodes because of their special morphology and high specific surface areas. These titanates provide high rate capability and low volume expansion upon lithiation. More importantly, their tubular structure helps the transport of ions through the crystal. In this study, we synthesized elongated titanate nanotubes and modified their interlayer distances by changing the pH (2–13). For the structural characterization XRD, BET, SEM and TEM techniques were used. In addition, the effect of interlayer distance on energy capacity and rate capability was investigated. The highest interlayer distance was obtained at pH 10 and with decreasing pH, the interlayer distance dropped until reaching a pH value of 4. Conversely, the specific surface area reached its maximum value of 204 m2 g−1 at a pH of 4. Different from anatase (TiO2), titanate nanotubes had broad peaks in cyclic voltammograms suggesting a pseudocapacitive behavior. The sloping profiles of potential-capacity results also supported the pseudocapacitive property. For the titanate nanotubes obtained at pH 10, an initial discharge capacity of 980 mAh g−1 was achieved. More importantly, titanate nanotubes showed exceptional rate capabilities and the capacities stayed almost constant at high current rates because of their elongated structure. It was found that the interlayer distance and the elongated structure play an important role in the electrochemical performance of the material. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) and two-dimensional (2D) titania/titanate nanostructures are fabricated directly on a self-source metallic titanium (Ti) surface via in situ surface re-construction of a Ti substrate using potassium hydroxide (KOH) under a hydrothermal (HT) condition. The effect of temperature and the concentration of KOH on the variations in morphology and titania-to-titanate phase changes are studied and explained in detail. A growth model is proposed for the formation process of the platelet-to-nanorod conversion mechanism. The field emission (FE) properties of titania/titanate nanostructures are studied, and the effects of the morphologies (such as 1D nanorods, 2D nanoplatelets, and a mixture of 1D nanorods and 2D platelets) on the FE properties of the samples are investigated. The samples depict a reasonable low turn-on field and emission stability. The FE mechanism is observed to follow standard Fowler–Nordheim (FN) electron tunneling. The geometrical field enhancement factor (β) is measured to be very high, and is compared with theoretical values calculated from various existing models to explore the feasibility of these models. The surface modification of metallic Ti by a simple non-lithographic bottom-up method and the low-macroscopic FE properties can provide a potential alternative to field emission displays for low-power panel technology. [ABSTRACT FROM AUTHOR]

In this work, fully a-axis oriented SrTiO3 thin films were synthesized by ink-jet printing of water-based precursor inks. The developed precursor solution or ‘ink’ was optimized in terms of rheology, leading to the ejection of single droplets showing a maximum contact angle of 12° on (100) oriented single crystal LaAlO3 substrates. By using the appropriate ink-jet deposition parameters and thermal treatment, well-textured and dense SrTiO3 films of 130 nm thickness were obtained. The biaxial texture is maintained up to the surface of the films, leading to the formation of (h00)-oriented terraces. As shown by transmission electron microscopy, excellent texture transfer was achieved from the SrTiO3 film to the YBa2Cu3O7 − δ layer deposited by pulsed laser deposition. Outstanding superconducting properties were obtained with critical current densities up to 3.6 MA cm−2 in self-field at 77 K, demonstrating that these sustainable SrTiO3 films meet the requirements to be used as growing template for high quality superconducting coatings. [ABSTRACT FROM AUTHOR]

A novel three degree-of-freedom microactuator based on thin-film lead-zirconate-titanate (PZT) is described with its detailed structural model. Its central rectangular-shaped mirror platform, also referred to as the stage, is actuated by four symmetric PZT bending legs such that each leg provides vertical translation for one corner of the stage. It has been developed to support real-time in vivo vertical cross-sectional imaging with a dual axes confocal endomicroscope for early cancer detection, having large displacements in three axes (z, θx, θy) and a relatively high bandwidth in the z-axis direction. Prototype microactuators closely meet the performance requirements for this application; in the out-of-plane (z-axis) direction, it has shown more than 177 μm of displacement and about 84 Hz of structural natural frequency, when two diagonal legs are actuated at 14V. With all four legs, another prototype of the same design with lighter stage mass has achieved more than 430 μm of out-of-plane displacement at 15V and about 200 Hz of bandwidth. The former design has shown approximately 6.4° and 2.9° of stage tilting about the x-axis and y-axis, respectively, at 14V. This paper also presents a modeling technique that uses experimental data to account for the effects of fabrication uncertainties in residual stress and structural dimensions. The presented model predicts the static motion of the stage within an average absolute error of 14.6 μm, which approaches the desired imaging resolution, 5 μm, and also reasonably anticipates the structural dynamic behavior of the stage. The refined model will support development of a future trajectory tracking controller for the system. [ABSTRACT FROM AUTHOR]

We show that hydrogen titanate (H2Ti3O7) nanotubes form strongly associated reversible nano-bio-conjugates with the vital respiratory protein, cytochrome c. Resonance Raman spectroscopy along with direct electrochemical studies indicate that in this nano-bio-conjugate, cytochrome c exists in an equilibrium of two conformational states with distinctly different formal redox potentials and coordination geometries of the heme center. The nanotube-conjugated cytochrome c also showed enhanced peroxidase activity similar to the membrane-bound protein that is believed to be an apoptosis initiator. This suggests that such a nanotube-cytochrome c conjugate may be a good candidate for cancer therapy applications. [ABSTRACT FROM AUTHOR]

Lead-free barium zirconate-titanate/barium calcium-titanate, [(BaZr0.2Ti0.80)O3]1[?]x-[(Ba0.70Ca0.30)TiO3]x (x = 0.10, 0.15, 0.20) (BZT-BCT) ceramics with high dielectric constant, low dielectric loss and moderate electric breakdown field were prepared by the sol-gel synthesis technique. X-ray diffraction patterns revealed tetragonal crystal structure and this was further confirmed by Raman spectra. Well-behaved ferroelectric hysteresis loops and moderate polarizations (spontaneous polarization, Ps [?] 3-6 uC cm[?]2) were obtained in these BZT-BCT ceramics. Frequency-dependent dielectric spectra confirmed that ferroelectric diffuse phase transition (DPT) exists near room temperature. Scanning electron microscope images revealed monolithic grain growth in samples sintered at 1280 degC. 1000/e versus (T) plots revealed ferroelectric DPT behaviour with estimated g values of [?]1.52, 1.51 and 1.88, respectively, for the studied BZT-BCT compositions. All three compositions showed packing-limited breakdown fields of [?]47-73 kV cm[?]1 with an energy density of 0.05-0.6 J cm[?]3 for thick ceramics (>1 mm). Therefore these compositions might be useful in Y5V-type capacitor applications. [ABSTRACT FROM AUTHOR]

Lead strontium titanate (Pb0.5Sr0.5)TiO3 (PST) nanotube arrays are prepared by a sol-gel and spin-coating process using an anodic aluminium oxide template. The structure and morphology of the as-prepared sample are characterized by x-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results show that the as-prepared PST sample possesses a perovskite structure with a relatively uniform diameter of about 200 nm. Photoluminescence (PL) spectrum of the sample shows emission bands centered at about 2.87eV at room temperature, which consists of three intense emission sub-bands at 3.02, 2.87 and 2.76eV, respectively. The energy corresponding to the central PL peak is lower than the band-gap energy (3.2eV) of PST bulk materials, which may originate from the size effect of the PST nanotube arrays. The multi-peaks in the PL spectrum may be attributed to the radiative recombination of trapped electrons and holes in tail and gap states induced by local defect and oxygen vacancies. The Raman scattering spectrum of the PST nanotube arrays, which are obviously broadened in comparison with the bulk materials, show that their phonon modes are in agreement with those allowed in the tetragonal phase. [ABSTRACT FROM AUTHOR]

Differential analysis of current-voltage characteristics, obtained on the surface of epitaxial films of ferroelectric lead zirconate titanate (Pb(Zr0.2Ti0.8)O3) using scanning probe microscopy, was combined with spatially resolved mapping of variations in local conductance to differentiate between candidate mechanisms of local electronic transport and the origin of disorder. Within the assumed approximations, electron transport was inferred to be determined by two mechanisms depending on the magnitude of applied bias, with the low-bias range dominated by the trap-assisted Fowler-Nordheim tunneling through the interface and the high-bias range limited by the hopping conduction through the bulk. Phenomenological analysis of the I-V curves has further revealed that the transition between the low- and high-bias regimes is manifested both in the strength of variations within the I-V curves sampled across the surface, as well as the spatial distribution of conductance. Spatial variations were concluded to originate primarily from the heterogeneity of the interfacial electronic barrier height with an additional small contribution from random changes in the tip-contact geometry. [ABSTRACT FROM AUTHOR]

Hydrogen/sodium titanate nanotubes (TNTs) were investigated as hydrogen (H2) sensors. TNT films exhibit good sensing properties and a large response, in particular at room temperature. Electrical conductivity measurements performed under different atmospheres from 25 to 300 degC indicate that, for T > 100 degC, conduction is thermally activated and can be attributed to electronic transport, whereas for T < 100 degC conduction is dominated by protonic transport. The T dependence of the H2 sensitivity was determined and related to this variation in the dominant transport mechanism. For low T, H2 sensing originates from the modulation in protonic conduction. Such modulation was attributed to the creation/destruction of surface hydroxyl groups. [ABSTRACT FROM AUTHOR]

A weak-polyelectrolyte multilayer on a surface of titanate nanobelts (Ti-NBs) was utilized as a template for in situ Ag nanoparticle formation in the fabrication of Ag-loaded Ti-NBs nanocomposites. The polyelectrolyte multilayer (PEM) was fabricated using layer-by-layer self-assembly of poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) on the surface of high-surface-area titanate nanobelts (Ti-NBs) synthesized using a hydrothermal procedure. The concentration of Ag nanoparticles in the PEM was controlled by repeating the ion-loading/reduction cycle. The subsequent annealing of the Ag/Ti-NBs-PEM nanocomposites yielded nanostructured crystalline Ag/Ti-NBs. Transmission electron microscopy (TEM) techniques (HRTEM, SAED) and x-ray powder diffraction (XRD) were employed to evaluate the morphological, structural and growth characteristics of the silver nanocrystallites in the Ag/Ti-NBs nanocomposites. The UV-vis photoactivity of the as-fabricated nanocomposites was monitored by the degradation of the cationic dye methylene blue (MB). An enhanced UV photo-efficiency was observed for the Ag/Ti-NBs nanocomposites compared with pure Ti-NBs. As-fabricated Ag(x)/Ti-NBs nanocomposites also exhibited visible photoactivity assisted by the near-field amplitudes of the localized surface plasmon resonance (LSPR) of the silver nanoparticles in the 1D nanocomposite. [ABSTRACT FROM AUTHOR]

Epitaxial thin films of cobalt ferrite (CFO) single layer and CFO-lead zirconium titanate (PZT) bilayers were deposited on single crystal MgO (1 0 0) and SrTiO3 (STO) (1 0 0) substrates by pulsed laser deposition. The structural properties were characterized using x-ray diffraction and atomic force microscopy. The magnetic properties of the as-grown thin films were measured at 10 and 300 K in both parallel and perpendicular magnetic fields. The CFO-PZT bilayer films showed enhanced or reduced values of magnetization as compared with those of the CFO single layer films depending on the substrate of deposition. A strain compression-relaxation mechanism was proposed in order to explain the structure-property relationships in the CFO-PZT bilayer thin films. [ABSTRACT FROM AUTHOR]

A three degree-of-freedom (DOF) micro-motor comprising a hollow cylindrical transducer with slots novelly inserted, mounted to a lead zirconium titanate (PZT) piezoelectric element, was developed. Reversible rotation about three orthogonal axes was obtained at frequencies above 190 kHz. The peak torque about the transverse (x and y) and longitudinal (z) axes was 1.33, 1.23 and 2.38 nNm, respectively, at 21.2 VRMS. An electrical control scheme was employed to demonstrate the ability to operate these micro-motors at the low speeds necessary for many applications, including minimally invasive surgery (MIS). This micro-motor represents a significant step towards the development of true microscopic multi-DOF actuators, which can be integrated with MIS equipment, for example, in order to provide surgeons with better operability, dexterity and control deep within a patient's body. [ABSTRACT FROM AUTHOR]

PZT/LCT/PA (lead zirconate titanate Pb(Zr1[?]xTix)O3/Liquid crystalline thermosets/polyamide) composites of 0-3 connectivity were fabricated by hot-pressing. Commercially available PZT powder was calcined at different temperatures for the optimization of the composite properties. The phase transition during calcination of the powder was studied by x-ray diffraction and the particle size by light scattering and scanning electron microscopy. The relative permittivity er, piezoelectric charge constant d33, conductivity s and elastic modulus E of the composites were found to increase with increasing ceramic volume fraction ph. The obtained d33 and g33 values of this newly developed PZT/LCT/PA composite with 50 vol% PZT using a low poling voltage of 60 kV cm[?]1 and poling time of 30 min are 42 pC N[?]1 and 65 mV m N[?]1, respectively, which are high values for this volume fraction in comparison with the other 0-3 composites reported. Good agreement was found between the experimental data of relative permittivity and piezoelectric constants with several theoretical models (Jayasundere, Yamada and Lichtenecker) of 0-3 composites. In order to assess the correlation of the experimental data with the theoretical models, the experimental data obtained from PZT/PA composites were also included. [ABSTRACT FROM AUTHOR]

Raman-scattering spectroscopy on the microscale is proposed as a method to study the distribution of defects and existing vacancies in lead zirconate titanate (PZT) fibres during industrial processes to monitor the volumetric structural order within the fibre and to estimate the spatial phase transition degree from rhombohedral to tetragonal phase.PZT fibres developed in two different sintering atmospheres, PbO and a mixture of PbZrO3 and ZrO2 (PZ+Z), were studied to determine optimal conditions for the production of defect-free PZT fibres. An estimation of defect distribution along the radius of the PZT fibres is presented using Raman spectroscopy and confirmed by x-ray-diffractometry measurements. The degradation of the spatial-mechanical properties is explained by structural changes produced by electrostatic interactions between Zr and Ti ions. [ABSTRACT FROM AUTHOR]

This work examined charge build-up and re-distribution in SrTixNb1[?]xO3 quantum wells and TiO2-SrTiO3 heterostructure based on thermoelectric power data reported in the literature. In this work, we first identified the equations that best related charge density to the thermoelectric power. Using such equations together with a distributed model that accounted for the layered structure, we computed the charge densities in the two structures over a broad temperature range. Our findings suggested that charge migration from the quantum wells into the substrate was primarily governed by the barrier height at the interface. A very different charge density profile was observed in the heterostructure and the computed charge spread into the substrate was immense (of the order of hundreds of micrometres). By comparing such charge spread with values taken from samples when the TiO2 top layer had been removed, we arrived at the conclusion that it could not have originated from the interface and must have arisen from other sources such as oxygen vacancies (acting as donors) embedded during film deposition. [ABSTRACT FROM AUTHOR]

We present an effective way in this paper to increase the density of lanthanum doped bismuth titanate ceramics, Bi4--xLaxTi3O12 (BLT), thereby significantly improving the performance of the BLT ceramics. Dense BLT ceramicses, Bi4--xLaxTi3O12 (x = 0.25, 0.5, 0.75, 1.0), are prepared by using nanocrystalline powders fabricated by a --gel method and high-pressure technique. The microstructures of the BLT ceramicses prepared separately by conventional-pressure and high-pressure techniques are investigated by using x-ray diffraction and transmission electron microscope. The influence of La-doping on the densification of bismuth titanate ceramics is investigated. The experimental results indicate that the phase compositions of all samples with various lanthanum dopings sintered at 900 degC possess layer-structure of Bi4Ti3O12. The green compacts are pressed under 2.5 GPa, 3.0 GPa, 3.5 GPa and 4.0 GPa, separately. It is found that the density of BLT ceramics is significantly increased due to the decreasing of porosity in the green compacts by high-pressure process. [ABSTRACT FROM AUTHOR]

This paper reports that the transverse laser induced thermoelectric voltages (LITV) are observed for the first time in the step flow growth (1 -- x)Pb(Mg1/3Nb2/3)O3--xPbTiO3 (PMN-PT, x = 0.20, 0.33, 0.50) thin films deposited on vicinal-cut strontium titanate single crystal substrates. Because lead magnesium niobate-lead titanate is a solid solution of lead magnesium niobate (PMN) and lead titanate (PT), there are two types of signals. One is wide with a time response of a microsecond, and the other superimposed with the wide signal is narrow with a time response of a nanosecond. The transverse LITV signals depend on the ratio of PMN to PT drastically. Under the irradiation of 28-ns pulsed KrF excimer laser with the 248-nm wavelength, the largest induced voltage is observed in the 0.50Pb(Mg1/3Nb2/3)O3--0.50 PbTiO3 films. Moreover, the effects of film thickness, substrates, and tilt angles of substrates are also investigated. [ABSTRACT FROM AUTHOR]

We report on an unusual crystallization phenomenon that results in the self-assembly of sub-micron tubules of crystalline SrTiO3. The deposition of the tubular structures was done in the pores of anodized aluminum oxide templates by the electrophoretic deposition of SrTiO3 sols and subsequent annealing. Homogeneous nucleation inside the pores produces a critical number of crystallites leading to their self-organization when the nanocrystals reach sizes that equal the mean free distances between the nuclei. Due to steric constraints the crystals start to organize in order to most efficiently fill the available surface of the pore walls. This process leads to the formation of domains containing a large number of idiomorphic SrTiO3 nano-cubes that are self-aligned into almost perfect cube-on-cube and cube-to-wall registry, which makes up the walls of the tubules. The described mechanism shows the ability of nanocrystals with well defined morphologies to adapt spatial constraints and self-organize into desired geometries. [ABSTRACT FROM AUTHOR]

Piezoelectric actuators outperform other technological solutions in the area of high-speed, high-force and high-accuracy displacement, but are only able to generate strains of about 0.2%. The load capability is generally quantified in terms of a blocking force, which is the force sustained under electric field at zero displacement. Stress-strain curves in a temperature regime from room temperature up to 150 degC on electrically loaded soft lead zirconate titanate (PZT) are generated to determine the blocking stress. The ensuing nonlinear behaviour is discussed in terms of ferroelectric and ferroelastic switching and contrasted to idealized linear constitutive behaviour as often assumed by manufacturers. The blocking stress is shown to increase with temperature due to an additional stiffening effect as a function of electric field. The actual mechanical work done is found to be larger than in the idealized case where linear constitutive behaviour is assumed. [ABSTRACT FROM AUTHOR]

We have investigated by means of noise spectroscopy the transport properties of half-metal La0.7Ba0.3MnO3 (LBMO) thin films deposited on MgO substrates. A reduced metal-insulator transition temperature and a peculiar noise behaviour are observed in the films grown on MgO substrates, when compared with similar films grown on SrTiO3 substrates. In particular, a large increase in noise is observed below the metal-insulator transition temperature, associated with a current induced reduction in the excess noise level. This finding is explained in terms of the spin torque effect between regions with depressed Curie temperatures among the ferromagnetic metallic domains. The proposed theoretical model, taking into account the half-metal character of manganites, describes well the experimental data. [ABSTRACT FROM AUTHOR]

Multifunctional transparent ferroelectric ceramics have widespread applications in electro-optical devices. Unfortunately, almost all currently used electro-optical ceramics contain a high lead concentration. In this work, via coupling of spark plasma sintering with high pressure, we have successfully synthesized bulk lead-free transparent nanostructured BaTiO3 (abbreviated as BTO) and SrTiO3 (STO) ceramics with excellent optical transparency in both visible and infrared wavelength ranges. This success highlights potential ingenious avenues to search for lead-free electro-optical ceramics. [ABSTRACT FROM AUTHOR]