Search Results (75)

In this study, lanthanum–nitrogen co-doped titanium dioxide (La-N-TiO₂) thin films were fabricated using Ion Beam Assisted Deposition (IBAD) and subjected to accelerated ultraviolet (UV) aging experiments to systematically investigate the impact of co-doping on the films’ resistance to UV aging. X-ray diffraction (XRD) analysis revealed that La-N co-doping inhibits the phase transition from anatase to rutile, significantly enhancing the phase stability of the films. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) characterizations indicated that co-doping increased the density and surface uniformity of the films, thereby delaying the expansion of cracks and increase in roughness induced by UV exposure. Energy-dispersive X-ray spectroscopy (EDS) results confirmed the successful incorporation of La and N into the TiO₂ lattice, enhancing the chemical stability of the films. Contact angle tests demonstrated that La-N co-doping markedly improved the hydrophobicity of the films, inhibiting the rapid decay of hydrophilicity during UV aging. After three years of UV aging, the co-doped films maintained high structural integrity and photocatalytic performance, exhibiting excellent resistance to UV aging. These findings offer new insights into the long-term stability of photovoltaic self-cleaning materials. Full article

The structural and electrical properties of double perovskite compounds SrLaFe_1−xMn_xTiO_6−δ (x = 0, 0.33, 0.67, and 1.0) were studied using X-ray diffraction (XRD) and dielectric impedance measurements. The reparation of perovskite compounds was successfully achieved through the precursor solid-state reaction in air at 1250 °C. The purity phase and crystal structures of perovskite compounds were determined by means of the standard Rietveld refinement method using the FullProf suite. The best fitting results showed that SrLaFeTiO_6−δ was orthorhombic with space group Pnma, and both SrLaFe_0.67Mn_0.33TiO_6−δ and SrLaFe_0.33Mn_0.67TiO_6−δ were cubic structures with space group Fm3m, while SrLaMnTiO_6−δ was tetragonal with a I/4m space group. The charge density maps obtained for these structures indicated that the compounds show an ionic and mixed ionic–electronic conduction. The dielectric impedance measurements were carried out in the range of 20 Hz to 1 MHz, and the analysis showed that there is more than one relaxation mechanism of Debye type. Doping with Mn was found to reduce the dielectric impedance of the samples, and the major contribution to the dielectric impedance was established to change from a capacitive for SrLaFeTiO_6−δ to a resistive for SrLaMnTiO_6−δ. The fall in values of electrical resistance may be related to the possible occurrence of the double exchange (DEX) mechanism among the Mn ions, provided there is oxygen deficiency in the samples. DC-resistivity measurements revealed that SrLaFeTiO_6−δ was an insulator while SrLaMnTiO_6−δ was showing a semiconductor–metallic transition at ~250 K, which is in support of the DEX interaction. The dielectric impedance of SrLaFe_0.67Mn_0.33TiO_6−δ was found to be similar to that of (La,Sr)(Co,Fe)O_3-δ, the mixed ionic–electronic conductor (MIEC) model. The occurrence of a mixed ionic–electronic state in these compounds may qualify them to be used in free lead solar cells and energy storage technology. Full article

This study focuses on addressing the reflectivity reduction issue in La_1–xSr_xTiO_3+δ during high-temperature preparation, which is caused by oxygen vacancy generation. Bulk samples of CeO₂-doped La_1–xSr_xTiO_3+δ with varying doping contents as a second phase and sintering temperatures were prepared. The phase composition, reflectivity, and valence states were thoroughly investigated. Introducing 10 wt.%CeO₂ significantly suppressed the formation of oxygen vacancies. Thus, the occurrence of impurity levels caused by oxygen vacancies was reduced. This can further mitigate the reflection decrease caused by impurity levels as photon absorption traps. Additionally, the reduced pore structure achieved at 1450 °C contributed to improved reflectivity compared to pure La_1–xSr_xTiO_3+δ. The findings suggest that this approach has great potential for reducing oxygen vacancies sensitivity in high-reflection ceramics under high-temperature conditions and preserving their optical properties. Full article

In this work, a novel potential thermal barrier coating material entropy-stabilized titanium–aluminum oxide (La_0.25Ce_0.25Nd_0.25Sm_0.25)Ti₂Al₉O₁₉ (META) was successfully synthesized by the solid-state reaction method, and its thermophysical properties, phase stability, infrared emissivity, mechanical properties, and CMAS corrosion resistance were systematically investigated. The results demonstrated that META exhibits low thermal conductivity at 1100 °C (1.84 W·(m·K)⁻¹), with a thermal expansion coefficient (10.50 × 10⁻⁶ K⁻¹, 1000–1100 °C) comparable to yttria-stabilized zirconia (YSZ). Furthermore, META displayed desirable thermal stability, high emissivity within the wavelength range of 2.5–10 μm, and improved mechanical properties. Finally, META offers superior corrosion resistance due to its excellent infiltration inhibiting. The bi-layer structure on the corrosion surface prevents the penetration of the molten CMAS. Additionally, doping small-radius rare-earth elements thermodynamically stabilizes the reaction layer. The results of this study indicate that (La_0.25Ce_0.25Nd_0.25Sm_0.25)Ti₂Al₉O₁₉ has the potential to be a promising candidate for thermal barrier coating materials. Full article

The increased production of biodiesel results in a corresponding rise in the production of glycerol (GLY) as a by-product. The selective oxidation of glycerol can yield relatively simple products under mild reaction conditions, offering high added value and positioning it as one of the most promising methods for industrialization. In this study, we employed black titanium dioxide (B-TiO₂) as a support and deposited platinum (Pt) to create a noble metal-supported catalyst. Lanthanum (La) or cerium (Ce) was doped into B-TiO₂ to enhance the concentration of oxygen vacancies in the support, thereby improving catalyst activity. Throughout the research process, we also investigated the impact of varying amounts of La or Ce doping on catalyst performance. Analysis of the catalytic experimental data revealed that Pt/30%Ce-B-TiO₂ exhibited the highest catalytic performance. Structural analysis of the catalysts showed that the synergistic effect between Pt⁰ and oxygen vacancies contributed to enhancing catalyst activity. Full article

As a carbon-neutral and renewable raw material, cellulose can be transformed into biomass fuels to reduce the dependence on fossil fuels and carbon dioxide emissions. In view of harsh reaction conditions, low selectivity of product, and easy deactivation of the catalyst, this study studied the use of photothermal catalytic technology to convert cellulose into bio-oil rich in levulinic acid. It was discovered that a synergistic effect between heating and photocatalysis is present in cellulose degradation. Different metals were loaded on carbon nanotubes doped with titanium dioxide to prepare different photothermal catalysts, and their catalytic effects on cellulose were compared. It was found that TiO₂-CNT loaded with platinum metal exhibited the highest catalytic performance. By adopting Pt/TiO₂-CNT as the catalyst, the conversion rate of bio-oil reached 99.44%, and the selectivity of LA reached 44.41% at 220 °C for 3 h. As the photothermal catalysis increased the H/C ratio and decreased the O/C ratio of the liquid product, the calorific value reached 21.01 MJ/kg. This study can promote the further industrial application of lignocellulose to prepare fuel oil and decrease the environmental pollution caused by the massive consumption of fossil fuels. Full article

Thermodynamic calculations were carried out on typical tungsten cathode materials using Factsage software within a temperature range of 1000–3400 °C. The relationship between the phase stability and electron emission performance of the cathode in a vacuum environment and under a protective atmosphere was investigated. The thermodynamic stability of tungsten cathodes doped with different proportions of carbides and oxides was calculated. It was found that when the doped phase (ThO₂, La₂O₃, Y₂O₃, Lu₂O₃, Er₂O₃, Gd₂O₃, TiO₂, ZrO₂, HfO₂, ThC₂, LaC₂, YC₂, TiC, ZrC, and HfC) in the cathode starts to be consumed, the electron emission performance of the cathode will decline. Therefore, the high-temperature stability of the doped phase carbides and oxides also affects the operating temperature of the cathode. To verify these results, this study tested the electron emission performance of W–La₂O₃, W–ThO₂, W–ZrO₂, W–ZrC, and W–HfC, plotting their volt–ampere characteristic curves. The results indicated that the W-La₂O₃ cathode exhibits the best emission performance at low temperatures, while the W-ThO₂, W–ZrO₂, W–ZrC, and W–HfC cathodes showed better emission performance at high temperatures. The experimental results are in good agreement with the simulation results. The thermal stability of the doped phase is closely related to the high-temperature thermal stability of the cathode. Full article

Water molecules from the environment or human breath are one of the main factors affecting the accuracy, efficiency, and long-term stability of electronic gas sensors. In this contribution, yttrium (Y)-doped La₂Ti₂O₇ (LTO) nanosheets were synthesized by a hydrothermal reaction, demonstrating improved proton conductivity compared to their non-doped counterparts. The response of Y-doped LTO with the optimal doping concentration to 100 ppm NO₂ at 43% relative humidity (RH) was −21%, which is four times higher than that of bare La₂Ti₂O₇. As the humidity level increased to 75%, the response of Y-doped LTO further increased to −64%. Unlike the gas doping effect observed in previous studies of semiconducting metal oxides, the sensing mechanism of Y-doped LTO nanosheets is based on the enhanced dissociation of H₂O in the presence of target NO₂ molecules, leading to the generation of more protons for ion conduction. This also resulted in a greater resistance drop and thus a larger sensing response at elevated humidity levels. Our work demonstrates that proton-conductive oxide materials are promising gas-sensing materials under humid conditions. Full article

In hydrogen processes, managing CO emissions and removal by catalytic oxidation is crucial during H₂ production, storage/transportation, and use, ensuring the efficiency and safety of hydrogen systems and contributing to more sustainable energy solutions. Perovskite-structured transition metal oxide catalysts have been widely studied in various energy and environmental applications due to their extensive compositional modifications and electronic adjustments, facilitating catalytic behavior. Here, Ce-based perovskite catalysts with dual active metal doping at varying Co and Ni ratios are investigated to understand their structural and redox properties in CO oxidation. The reaction mechanism involves CO adsorption, oxygen activation, and redox cycling, confirming catalytic turnover. In situ DRIFTS analysis reveals real-time surface transformations with catalytic activity, which vary with Co and Ni doping ratio. Relatively, CO adsorption on Co³⁺ dominates the low-temperature activity, whereas Ni contributes to the efficiency at elevated temperatures. LCCNTxy (La_0.7Ce_0.1Co_xNi_yTi_0.6O₃) with x = 0.3 and y = 0.1 exhibits the highest performance, achieving T₁₀ above 40 °C and the fastest T₉₀ at 230 °C. This study highlights the compositional tuning in dual-doped perovskites and complementary roles of Co and Ni in CO oxidation for developing efficient industrial catalysts. Full article

Relaxor ferroelectric film capacitors exhibit high power density with ultra-fast charge and discharge rates, making them highly advantageous for consumer electronics and advanced pulse power supplies. The Aurivillius-phase bismuth layered ferroelectric films can effectively achieve a high breakdown electric field due to their unique insulating layer ((Bi₂O₂)²⁺ layer)). However, designing and fabricating Aurivillius-phase bismuth layer relaxor ferroelectric films with optimal energy storage characteristics is challenging due to their inherently stable ferroelectric properties. In this work, lead-free CaBi_4-xLa_xTi₄O₁₅ films were synthesized using the sol–gel technique and a weakly coupled relaxor design. On one hand, the introduction of La³⁺ ions weaken the dipole–dipole interactions, thereby enhancing the relaxor behavior. Alternatively, the expansion of grain size is restricted to enhance the number of grain boundaries, which possess improved insulating properties. This leads to a higher breakdown electric field. The results indicate that CaBi_4-xLa_xTi₄O₁₅ (x = 1.0) films exhibit excellent recoverable energy storage density (70 J/cm³) and high energy efficiency (73%). Moreover, the film exhibited good temperature stability and frequency stability. This study not only identifies a promising material for dielectric film capacitors but also demonstrates that the energy storage capabilities of Aurivillius-phase bismuth layer ferroelectric films can be effectively modulated through a design incorporating weakly coupled relaxor characteristics. Full article

The microwave dielectric properties of (1−x)Ca_0.6(La_0.9Y_0.1)_0.2667TiO₃-x(Nd_1/2La_1/2)(Mg_(1+δ)1/2Ti_1/2)O₃ ((1−x)CYTO-xNLMTO) ceramics were investigated in this study. It was discovered that the addition of 1 wt% CuB₂O₄ effectively enhanced the densification and improved the microwave dielectric properties of (1−x)CYTO-xNLMTO, where δ = 0.02. The new ceramic systems of (1−x)CYTO-xNLMTO could achieve ultra-low loss and a high dielectric constant. The novel ceramic systems comprising (1−x)CYTO-xNLMTO exhibited remarkably low loss and a significantly high dielectric constant. Full article

This study examines the effects of La³⁺ doping on (Pb_0.75Ba_0.25)(Zr_0.70Ti_0.30)O₃(PBZT) ceramics, which were synthesized using the conventional solid-state reaction method. X-ray diffraction analysis confirmed that the PBZT structure, including PBZT doped with La³⁺ at concentrations x = 1 at.% and x = 2 at.%, exhibited a rhombohedral (R3c) space group, while higher doping levels of x = 3 at.% and x = 4 at.% led to a dominant cubic (Pm-3m) phase with approximately 30% of a remnant rhombohedral component. Scanning electron microscopy (SEM, JEOL JSM-7100F TTL LV, Jeol Ltd., Tokyo, Japan) and energy dispersive X-ray spectroscopy (EDS) were utilized to investigate the structure and morphology of these ceramics. The findings indicated that the chemical composition of the ceramic samples closely corresponded to the initial stoichiometry of the ceramic powder. An increase in the amount of lanthanum results in a decrease in the average grain size of the ceramics. The electrical properties were further evaluated using complex impedance spectroscopy (IS) over a range of temperatures and frequencies, as well as temperature dependence of DC conductivity. The similarity in the changes in activation energy for DC conductivity and grain boundary conductivity, caused by lanthanum ion modification, allows for the conclusion that grain boundaries are the primary microstructural element responsible for conductivity in these materials. Full article

Lead-boron special glass was doped into Ba_0.996La_0.004Ti_0.999O₃ (BLT4) ceramics in order to control the sintering process and grain growth, consequently obtaining materials with a well-developed microstructure. Changes in the microstructure resulted in a significant decrease in electrical permittivity along with a substantial increase in its frequency dispersion. Glass-doped ceramics, similar to pure BLT4, are characterized by a first-order phase transition from the ferroelectric phase to the paraelectric phase. The temperature of this transition shifts slightly towards higher values with the increase in glass dopant concentration. Full article

The remarkable stability, suitable thermomechanical characteristics, and acceptable electrical properties of donor-doped strontium titanates make them attractive materials for fuel electrodes, interconnects, and supports of solid oxide fuel and electrolysis cells (SOFC/SOEC). The present study addresses the impact of processing and thermochemical treatment conditions on the electrical conductivity of SrTiO₃-derived ceramics with moderate acceptor-type substitution in a strontium sublattice. A-site-deficient Sr_0.85La_0.10TiO_3−δ and cation-stoichiometric Sr_0.85Pr_0.15TiO_3+δ ceramics with varying microstructures and levels of reduction have been prepared and characterized by XRD, SEM, TGA, and electrical conductivity measurements under reducing conditions. The analysis of the collected data suggested that the reduction process of dense donor-doped SrTiO₃ ceramics is limited by sluggish oxygen diffusion in the crystal lattice even at temperatures as high as 1300 °C. A higher degree of reduction and higher electrical conductivity can be obtained for porous structures under similar thermochemical treatment conditions. Metallic-like conductivity in dense reduced Sr_0.85La_0.10TiO_3−δ corresponds to the state quenched from the processing temperature and is proportional to the concentration of Ti³⁺ in the lattice. Due to poor oxygen diffusivity in the bulk, dense Sr_0.85La_0.10TiO_3−δ ceramics remain redox inactive and maintain a high level of conductivity under reducing conditions at temperatures below 1000 °C. While the behavior and properties of dense reduced Sr_0.85Pr_0.15TiO_3+δ ceramics with a large grain size (10–40 µm) were found to be similar, decreasing grain size down to 1–3 µm results in an increasing role of resistive grain boundaries which, regardless of the degree of reduction, determine the semiconducting behavior and lower total electrical conductivity of fine-grained Sr_0.85Pr_0.15TiO_3+δ ceramics. Oxidized porous Sr_0.85Pr_0.15TiO_3+δ ceramics exhibit faster kinetics of reduction compared to the Sr_0.85La_0.10TiO_3−δ counterpart at temperatures below 1000 °C, whereas equilibration kinetics of porous Sr_0.85La_0.10TiO_3−δ structures can be facilitated by reductive pre-treatments at elevated temperatures. Full article

The current study aims to synthesize and analyze both pure and La-doped TiO₂, and evaluate the photocatalytic and antibacterial activity of as-prepared samples. Doped and undoped samples were prepared by the non-hydrolytic sol–gel method from titanium(IV) chloride, benzyl alcohol, and lanthanum(III) nitrate followed by thermal treatment. Lanthanum content in synthesized samples was 0.4, 1, and 5 mol%. The resulting nanopowders’ structure and morphology were described using XRD, IR, and UV–Vis analysis. The average particle sizes of pure and doped TiO₂ were about 6–15 nm and anatase was found to be a dominant crystalline phase in the samples. It was observed that particle sizes decreased on increasing La content. The photocatalytic activity of the pure and La-doped sol–gel powders was estimated in the decomposition of paracetamol in distilled water using ultraviolet light illumination. Doping with lanthanum ions has been shown to increase the photocatalytic properties on the degradation of paracetamol. Furthermore, the annealed catalysts (pure and La³⁺ doped) showed increased photocatalytic activity and degradation of the analgesic in comparison with non-annealed materials. In both cases, the highest photocatalytic efficiency is observed at the optimal La³⁺ (1 mol%) concentration. The antimicrobial activity of 1 mol% La/TiO₂ was tested against a reference strain E. coli in the presence of ultraviolet light and in dark conditions. The number of viable bacterial cells was determined by a spread plate method, and kill curves were performed. The results showed that photoactivated 1 mol% La/TiO₂ exhibited a strong bactericidal effect, and in concentration, 1 mg/mL efficiently killed bacteria at an initial cell density of about 10⁵ colony forming units in 1 mL within 15 min. Full article