Effects of particle size and polymorph type of TiO2 on the properties of BaTiO3 nanopowder prepared by solid-state reaction

Barium titanate photocatalysts with silver-manganese dual cocatalyst for carbon dioxide reduction with water

Titanate photocatalysts with suitable cocatalysts are promising candidates for photocatalytic CO2 reduction, with the use of water as an electron donor. Here, several barium titanates with various compositions were examined, and BaTi4O9 (BT4) was found to be the best photocatalyst with the assistance of an Ag cocatalyst for photocatalytic CO2 reduction to form CO. The photocatalytic activity was further enhanced by the use of MnOx as an additional cocatalyst to construct an Ag-MnOx/BT4 photocatalyst, where Ag and MnOx were selectively deposited at different facets on BT4 crystal and functioned as active sites for CO2 reduction and water oxidation, respectively. As for the oxidative products from water, molecular oxygen (O2) and hydrogen peroxide (H2O2) were obtained.

A Facile and Eco-Friendly Hydrothermal Synthesis of High Tetragonal Barium Titanate with Uniform and Controllable Particle Size

The preparation of tetragonal barium titanate (BT) powders with uniform and suitable particle sizes is a significant prerequisite for ultra-thin and highly integrated multilayer ceramic capacitors (MLCCs). However, the balance of high tetragonality and controllable particle size remains a challenge, which limits the practical application of BT powders. Herein, the effects of different proportions of hydrothermal medium composition on the hydroxylation process are explored to obtain high tetragonality. The high tetragonality of BT powders under the optimal solvent condition of water:ethanol:ammonia solution of 2:2:1 is around 1.009 and increases with the particle size. Meanwhile, the good uniformity and dispersion of BT powders with particle sizes of 160, 190, 220, and 250 nm benefit from the inhibition of ethanol on the interfacial activity of BT particles (BTPs). The core-shell structure of BTPs is revealed by different lattice fringe spacings of the core and edge and the crystal structure by reconstructed atomic arrangement, which reasonably explains the trend between tetragonality and average particle size. These findings are instructive for the related research on the hydrothermal process of BT powders.

Facile preparation and dielectric properties of BaTiO3 with different particle sizes and morphologies

BaTiO₃ nanoparticles were prepared by the hydrothermal method, and the effect of 1-(propyl-3-methoxysilyl)-3-methylimidazole chloride on the size of BaTiO₃ particles was investigated. The obtained BaTiO₃ was characterized by XRD, SEM, TEM, and Raman spectroscopy; and the dielectric properties of BaTiO₃ ceramic sheets were tested. The results indicate that the spherical BaTiO₃-N prepared without an ionic liquid was in a tetragonal phase with an average particle size of 129 nm. When an ionic liquid was added, the size of the BaTiO₃-IL decreased and the degree of agglomeration increased. In addition, with increasing quantity of ionic liquid, the tetragonal-phase content of BaTiO₃-IL gradually decreased until complete transformation into cubic phase. The dielectric constant of the BaTiO₃-N ceramics was the highest, and the dielectric constant decreased with decreasing BaTiO₃ particle size. Moreover, two types of BaTiO₃ nanoparticles (bowl- and sea urchin-shaped) were prepared by changing the hydrothermal conditions and additives. The average particle size of the former was 92 nm, the tetragonal-phase content was ca. 90%, and the dielectric constant was large; whereas the sea urchin-shaped BaTiO₃ consisted of small particles in the cubic phase, and the dielectric constant was small.

Development of Yttrium-Doped BaTiO3 for Next-Generation Multilayer Ceramic Capacitors

The use of electronic devices that incorporate multilayer ceramic capacitors (MLCCs) is on the rise, requiring materials with good electrical properties and a narrow band gap. This study synthesized yttrium-substituted barium titanate (Ba_1-x Y _x TiO₃, BYT) using a sol-gel process at 950 °C with varying concentrations of yttrium (0 ≤ x ≤ 0.3). X-ray diffraction analysis showed that the tetragonal phase became less pronounced as the yttrium content increased. The samples had varying grain sizes and porosity, with the BY30%T sample having the narrowest band gap at 2.21 eV. The BYT ceramic with 30% yttrium had a thermal conductivity of up to 7 W/m K and an electrical conductivity down to 0.002 (Ω cm)^-1 at 180 °C. The current-voltage characteristics of the BYT MLCC were also studied, showing potential use in next-generation high-capacity MLCCs. This work presents BYT as a promising material for these types of capacitors.

Functionality and Activity of Sol-Gel-Prepared Co and Fe co-Doped Lead-Free BTO for Thermo-Optical Applications

The BTO, BFTC, and BCTF compounds were synthesized by the sol-gel method. The XRD study revealed the formation of single-phase tetragonal perovskite structures with the space group (P4mm). The crystalline parameters were studied as a function of Fe and Co contents and occupation of Ba and/or Ti sites by Fe and Co in the BTO lattice. It was found that the obtained strain increases when Ba²⁺ is substituted by Co²⁺ and Ti⁴⁺ by Fe³⁺. The Raman investigation confirmed the existence of three active modes (B1/E (TO1LO), (E (TO)/A1(TO3), and (A 1(LO)/E (TO), all of which are related to the existence of the tetragonal phase and strongly support the XRD results. The microstructural study showed a clear correlation between the presence of Fe and Co and the grain size distribution. Optical studies revealed the improvement in band gap energy with transition-metal (Fe and Co) co-doped BTO ceramics. The decrease in the band gap is explained by the competing effects of Columbian interactions, microdeformation, and oxygen defects. The results indicate that the presence of Fe and Co dopants enhances the absorption in the BTO ceramic. The dopants demonstrated an effect on thermal conductivity: they decreased the thermal conductivity of BTO, which is in the range of 0.76-2.23 W m^-1 K^-1 at room temperature and 2.02-0.27 W m^-1 K^-1 at elevated temperatures. The microstructure of the manufactured materials and the grain size distribution affect the compressive strength.

Effects of Cu doping on electrochemical NOx removal by La0.8Sr0.2MnO3 perovskites

Electrochemical removal of nitrogen oxides (NO_x) by perovskite electrodes is a promising method due to its low cost, simple operation and no secondary pollution. In this study, a series of La_0.8Sr_0.2Mn_1-xCu_xO₃ (x = 0, 0.05, 0.1 and 0.15) perovskites are fabricated as the improved electrodes of solid electrolyte cells (SECs) for NO_x removal and the effects of Cu doping are investigated systematacially. Multiple characterization methods are carried out to analyze the physicochemical properties of perovskites firstly. Then the performances of cells based on various perovskites are evaluated by the measurements of electrochemical properties and NO_x conversions. The results show that the Cu-doped electrode has more surface oxygen vacancies and a better redox property, thus having a higher NO_x conversion and smaller polarization resistance. The electrode based on La_0.8Sr_0.2Mn_0.9Cu_0.1O₃ has the maximum 70.8% NO_x conversion and the lowest 36.3 Ω cm² R_p value in the atmosphere of 1000 ppm NO at 700 °C. First-principle calculation reveals that the Cu-doped electrode is easier to form surface oxygen vacancy, while the surface oxygen vacancy plays an important role on electron transfer between electrode and NO_x molecule. This study not only provides a new strategy to enhance the electrode performance for NO_x removal in SECs but reveals the fundamental effect of Cu doping on the properties of La_0.8Sr_0.2MnO₃ perovskites.

Sonochemical activation in aqueous medium for solid-state synthesis of BaTiO3 powders

BaTiO₃-based oxide compounds are important ceramic materials for multilayer ceramic capacitors. In this paper, we report a sonochemical activation process of BaCO₃ and TiO₂ in an aqueous medium for the synthesis of BaTiO₃ powders through a solid-state process. Owing to the physical and chemical effects of the ultrasonication in aqueous medium on the raw materials, BaTiO₃ powders could be successfully synthesized at relatively low temperatures through a solid-state reaction, which was significantly enhanced as compared to the case in ethanol medium. Detailed investigations on the resulting BaTiO₃ powders and ceramics were performed, and a model to understand the role of aqueous medium on the enhancement of the solid-state reaction was proposed in terms of Ba²⁺ ion leaching and zeta potential of TiO₂, which are strongly affected by the pH of the aqueous medium. Our results are not only helpful for cost-effective synthesis of BaTiO₃ through the highly reliable solid-state reaction process, but they also provide an understanding of the role of aqueous medium for the sonochemical process using raw materials with partial solubility in water.

Silane-treated BaTiO3 ceramic powders for multilayer ceramic capacitor with enhanced dielectric properties

Silane/ceramic combination provides the composites with several advantages from the advancements of new ceramic composite materials with good thermal conductivity, high mechanical and dielectric properties have wide significant applications in electrical and electronic industries. In this study, to enhance the dispersibility of dielectric barium titanate (BaTiO₃) ceramic powder and additives for the fabrication of multilayer ceramic capacitors (MLCCs), surface treatment of the precursor of ceramic powder was performed using silane coupling agents. Dielectric ceramic sheets fabricated from ceramic powders that had been surface-treated with different amounts of N-[3-(trimethoxysilyl)propyl]aniline (TMSPA) which increased the surface gloss. In particular, the dielectric properties of the multilayer ceramic sheet fabricated by stacking sheets from the TMSPA-treated ceramic powder sintering at 1200 °C, it was confirmed that the dielectric constant increased from 881 to 2382 and the dielectric loss dropped from 1.96 to 1.34% with utilization of the TMSPA treatment. The physical and dielectric properties of the TMSPA-treated multilayer ceramic sheet were also determined by Fourier-transform infrared spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, glossmetry, and electrochemical impedance analysis. The results revealed that the TMSPA-modified BaTiO₃ surfaces considerably increased the dielectric property of the fabricated nanocomposite.